Q – I haven’t done much to my 91 Carrera Cabrio for a couple years, and this spring, it is really showing it’s age. The rear window is cloudy and I think I might want it replaced. The top only releases from the top edge of the windshield, but it won’t go down; and neither of the windows are moving! I am wondering if all the expense is worth it. – David
A – Well, David, that last question puzzles me. It is a Porsche. If the body, engine, transmission, the fundamentals are all there, how could it not be worth it? I don’t stay up on values, but the C2 or C4 Cabrio is very desirable and I don’t think their value will drop any time soon. What would you do with your poor wounded car anyway? Donate it?
The only expensive part of your question is the rear window. Usually when they get nasty, the rest of the top is in equally shabby condition. So that IS going to hurt. Since it is a summer car, I suppose you could just leave it down and not drive it on rainy days. But then there is that problem with it not going down.
The top components that usually cause your symptom include the combi relay (on my car it was under the passengers side toe board) the micro switches (there are a few of them) the drive motor, cables and transmissions. I have seen a later style drive motor installed in a C2 that had the early style terminal (wrong size) plugged in and it worked…and for quite a while, with no problem. Then one day, the loose fitting terminal stopped making contact leading to an unnecessary and annoying repair bill to find it.
It could have been much worse. Obviously the original motor had failed and had already been replaced. It is a shame that the Bozo who replaced it didn’t replace the terminal at the same time. Maybe that same guy did yours too, and all it needs now is a terminal repaired. You can only hope, and hope that its easy to find.
Whether you replace the whole top or not, clearly you need to have the lack of function diagnosed. After that you can decide to have the cover repaired or not. If you don’t, it will soon become very annoying to crank it down and up manually. To determine the basic problem probably won’t be too expensive. Fixing it? Well, that is another chapter.
Since the windows worked last fall and went down once this spring, check the fuse first. If you find the fuse blown, replace it but don’t count on that being the end of the story. My guess is that one or both of the switches is failing. The switch paddles are under constant spring tension and the plastic will eventually fatigue and allow the paddle to go adrift. When this happens, the window motor may continue to receive power when you release a switch. This burns out the motor or if you are fortunate, blows the fuse. Of sometimes the switch simply fails to make contact internally from just laying dormant over the winter. Try some contact cleaner (available from Radio Shack) or try swapping switches.
On this generation, the switches are a lot easier to replace than on the early cars. In 1989 and prior, the switches had individual wire terminals that had to be plugged in one at a time. On your car, they simply unplug and plug right back in.
A useful tip: Those cheap switches in the unmarked white boxes may be tempting, based on the price. But the only good ones are European. Funny, those off brand switches even have names that sound like “Euro”, but don’t be fooled.
You know, David, the one thing you forgot to mention is oil leaks. If you haven’t noticed them, maybe you still have the under engine sound tray on the car. Or maybe you are in denial. That is one of the issues that could be a deal breaker for me. If I am facing a $3,000 bill for the top, and if the oil leaks are as bad as some I have seen, you could get upside down in this car quickly.
Knowing all this, I would have the car evaluated overall. I would have an experienced Porsche tech look at the whole car; not just to nail down the issues you know about, but for purposes of long range planning. Even with oil leaks, the car can still be a lot of affordable fun. Naturally, you should have the best car you can afford, but few of us can afford the newest version. And in the immortal words of C.S.N.Y.: “When you can’t be with the one you love, love the one you’re with”. – MC
Q – What does the intermediate shaft do and where is it?
A – The IMS is located in the lower section of the engine block, below the crankshaft and it is driven by the crankshaft. It is connected to the cylinder heads via the timing chains and it also drives the oil pump on many Porsche’s. In some of the newest engines, it has been eliminated altogether.
Q – I have never heard of a problem like this on any other engine, why does it happen to the Premier sports car of my dreams?
A – I assume that like all car companies, there is a raging battle between engineering and accounting. If the engineers made all the decisions, the accountants say they couldn’t afford to build it. So we the consumer, become the guinea pigs and when the warranty runs out, we pay the tab…but I digress. The failure of the system is rooted in the use of a sealed bearing at the flywheel end of the IMS. Sealed bearings are widely used in many parts of the car with great success. The problem is not the bearing itself, but the application in which it is used. A sealed bearing is filled with grease and the seal keeps the grease in (and presumably, contamination out). They are “lubricated for life” (oh yeah, I forgot, that is what marketing says!) The seals in these bearings rarely fail from the inside. The seal is usually breached from the outside. In the case of the IMS bearing, the outside is the inside of the crankcase which is bathed in hot, nourishing oil. (Confused yet?) The problem is, engine oil gets into the bearing past the seal, washes out the grease and leaves too little lubricant behind. The seal only allows enough oil in to do the dirty deed, not keep the bearing alive.
Q – Since you saw wetness at that seam, what should I do?
A – Now that the problem has become well exposed and documented, the oil leak at the rear of the engine should be checked out immediately. It was common to blame the crankshaft seal for a leak not realizing that a failing IMS bearing would cause the IMS flange seal to leak.
Q – Can you hear the bearing failing? Is there any other way to detect it?
A – My experience has shown that once you hear a bearing failure, damage is being done and in many cases, it is too late. With a stethoscope, we listen to the general vicinity of the IMS bearing at every service but usually the sound is subtle. I prefer oil analysis instead. A comment was made at the tech session that one could look for particulate inside the oil filter and I would take that concept a step further by having the oil analyzed to see what analysis reveals in the oil that one cannot possibly see with the naked (or even magnified) eye. Like the sound of a failed bearing, if you see particulate in your filter, you are in deep S*%$!
Q – What can I do to prevent it?
A – Change to a thicker viscosity oil of the proper Porsche specification. I use two brands here at the shop, Motul (French) and Pentosin (German), both are 05W40. Castrol Syntec 5w40 also carries Porsche approval. I still recommend Mobil One 0W40 for many cars but for these newer cars, I prefer the 05W40. On older engines, this recommendation does not apply so as always, follow the manufacturers recommendations! I also recommend using the correct oil filter specified for the engine, not a generic substitute. Other than that, I do not know how to prevent it. If I owned one of this generation, I would budget and plan to do the bearing retrofit.
Q – Who do you recommend for the IMS bearing retrofit?
A – I would only choose an experienced shop that employs ASE certified engine repair technicians. Delving into the bowels of a five figure Porsche engine should never be taken lightly. This is one operation where experience counts. I remember the first engine rebuild that I ever performed in1967. After three tries, I got it running but it never stopped leaking oil from the moment I fired it up. The moral of the story is: Don’t give this job to the “new guy”.
The IMS retrofit procedure isn’t much harder than doing an IMS flange reseal, so if the shop you’re thinking of using has done these procedures (as most that are familiar with Boxster, Cayman, or 911s are), a retrofit kit installation won’t be any more difficult than this. If your preferred shop is not on the list, have them contact us.
Why doesn’t the bearing on the other end of the intermediate shaft fail?
Well, there isn’t technically a bearing. The other end of the intermediate shaft rides in a bore of raw aluminum, splash oiled. Earlier aircooled Porsches and even later water-cooled GT2, GT3, and Turbo engines use split plain bearings (actually a VW Type 1 double-thrust camshaft bearing) that are oil fed on both ends of the shaft, with decades of proven reliability.
As supplied, the original IMS bearing employed a sealed bearing and relied on a permanent lubricant (grease) to lubricate the bearing. (Similar to the sealed bearing that fails in the gearboxes found in MY97-08 5 and 6 speed manual).
The problem with a sealed bearing with a permanent lubricant is that during the life of the bearing, the seal is subjected to oil temperatures near the maximum rating for the seal, eventually degrading the seal. At this point, the seal fails to retain the permanent grease, which is washed out by the engine oil. When this happens, the little amount of oil in the bearing is not sufficient to lubricate AND cool the bearing, leading to accelerated wear.
Several solutions have been suggested from more frequent replacement of the bearing and or seal and a lubrication schedule to replenish the permanent grease.
With our IMS Retrofit and IMS Upgrade, we chose to use a ceramic hybrid bearing which requires less lubrication and is designed specifically for poor lubrication environments. Coupled with the lack of grease seals, the new bearing is lubricated by splash as well as submersion lubrication
We do not recommend IMS retrofit kit installation as a do-it-yourself project – installation is best left to your trained independent mechanic or Porsche dealership. That said, typically the job is a billable 10-14 hours and average labor rates around the country are $140/hour. Later Tiptronic 911s require the engine and transmission to be removed together, so expect those cars to be very expensive when it comes time to do an IMS retrofit kit.By
Hi MC, You test drove my 2002 Carrera when I first bought it and I was concerned about the clutch. You mentioned that although the clutch felt fine and did not slip, you detected some oil seepage at the flange between the engine and transaxle. You cautioned me about the possibility of a seal failure and intermediate shaft concerns and I appreciated that info. Now after owning the car for a year or so, I am thinking about having the transmission removed and getting that oil issue looked into. I only have about 26,000 miles on the car. What is your opinion? Bill
A – Bill, first of all, thanks for allowing me the test drive. It’s the best part of my job! In this column, I have mentioned a concern about engines like yours for some time. When the cars were new or newer, Porsche took a very protective and supportive stance on the issue not even allowing independent technicians such as myself to gain an understanding of the failure by subsidizing replacement engines. If you wanted the old, broken engine, the core charge was almost as much as the replacement engine. A seasoned Porsche tech told me that it was an inside joke around the shop that part of the 30,000 mile service was an engine replacement!
So now the chickens have come home to roost. As these cars age, and as the problems have become apparent, the seal failures that have plagued them take on a new dimension now that Porsche is not helping out as they used to.
A couple weeks ago, I had the pleasure of visiting a colleague’s shop for a tech session where the matter of intermediate shaft (IMS) failure was very well covered in a slide presentation. Kudu’s Howard! If you get the Porsche E-brake news, it discussed in exhaustive detail there as well. I have excerpted some of the highlights and added some of the questions frequently posed to me as an adviser.
Q – I have a 1987 Porsche 924S and there is a water leak into the car. Every time it rains the passengers side floor gets wet. I don’t think it is the windshield since it leaked prior to having the windshield replaced and it still leaks with the new windshield. Joe
A – Under the battery, there is a clear path for water to enter the passenger side of the car. My advice is to remove the battery, clear the debris out of the area that may be blocking the drains and scrape the area clean. If the floor of the battery box is rotted out (which I am betting on) you can repair it in a few ways. 1) You could take it to a body shop where they can weld in a patch, 2) You could fashion a patch out of plastic which you can purchase at a plastic supply house, and glue it in with sealant, or 3) A piece of galvanized steel from a heating and cooling shop can be used. If you are going to have a body shop do it, they should be able to refinish it so it will be many years again before it rots. If you are going to do it yourself, a product called POR-15 can be applied over the rusty metal which then bonds to the rust. This provides a good basis for either a plastic patch or the steel patch. Bonding the patch to the area works well since the battery holds it in place until the sealant dries. That will cure the wet floor for years.
One thing to note is that both the positive and negative cables are black! Make sure you mark them before you remove the battery. If you don’t, and you are not sure which is which, use a volt/ohm meter to confirm which cable is ground. It is not worth taking any chances on this topic. – MC
Q – I am thinking of buying another Porsche. I have owned a 930 turbo, a 993 Cabriolet, and after I sold the cab, I got a muscle car. It is just not the same. I am looking at a Cayman S at the local dealer and I wonder if I should be concerned based on issues with the engine on the older cars. I am also considering buying a car from a private owner and then purchasing a service contract. Your opinion please. Tom
A – I know what you mean about those muscle cars, I once owned a Chevy 2 with a 350 and it was only fun in one mode, full throttle ¼ mile. It is a good thing that more muscle car owners will never drive a “furrin” car or the prices of pre-owned Porsches would skyrocket. Of course there is one muscle car that I like, my Hudson Hornet, but I admit it is a personal thing.
The Cayman will be an excellent choice for a number of reasons. All the bugs have been worked out. The engine is bulletproof. If you are buying from a Porsche dealer and the car is Certified Pre-Owned, the warranty is even better than a new car. Naturally you will pay more for the car than you would from a private owner, but when you buy a car from a dealer, you should expect that.
The warranty from Porsche is excellent. If you buy from a private owner, you can purchase a warranty but before you buy it, you had better have an attorney look at the contract and find out how they pay for repairs. I recently managed an order where the client had an extended warranty that reimbursed at a labor rate which the warranty company determined was the national prevailing rate. This resulted in extra out of pocket expense that cost hundreds of dollars for the “covered repair”. Even worse, numerous issues were not even covered at all due to various “weasel clauses” built into the contract. The factory sponsored warranties are far more comprehensive and fair. – MC
Q – On my 89 944 the hood shocks failed and I bought new ones but they are too long. I can’t get them on! Charlie
A – Yes they are too long and tricky to install too. If you disconnect them and lift the hood high enough to get the new ones on, you can break the windshield. I know, I have done that and it was quite expensive! So the trick is get two buddies to help. Have your friends hold up the hood while you install the bottom of the shock first. Then, with all your weight, get the shock compressed enough to slip in the top pin. They are super strong and you may curse a little but you can do it. Just don’t try to do it alone. And never grip the polished shafts with pliers or you will ruin the shocks. One last caution…when you are trying to lean on the shock to compress it, grip the body of the shock as tightly as you can…you’re going to be trying to pilot it into a bracket with a sharp corner, and if you slip, you can gash yourself pretty bad. Good luck! – MC
Q – On my 85 Carrera, after a 10 to 20 mile trip, I get a vibration and high pitched noise from the chassis that is driving my crazy. If I push the brake pedal hard, the noise goes away for a fraction of a mile then it comes back. I was convinced that it was a bad wheel bearing so I had my shop take the car apart and inspect the wheel bearings. They were fine and naturally, the noise was still there.
Then they thought it a splash shield rubbing on the rotor and indeed, there was a shiny spot on the splash shield. They bent it out of the way and on the test drive there was no noise. Then I drove it just over 10 miles or so and the noise came back. Next they thought it might be the brake rotors or pads so they serviced the rotors, and serviced the pads and indeed, the noise changed! After that, it would start after about 30 miles! Then they installed new pads. They drove the car about fifty miles and were very excited to report that the noise was GONE. I was thrilled! Then I took a trip north to the Flint area and about 60 miles out, the noise came back. I am so p—– off, I can’t see straight! Of course, every time I take the car in, they drive it and the car is quiet as a mouse! I know they are making an earnest effort to fix the car but they are simply out of ideas. Help! Larry
A – Holy cow, you have really suffered and it sounds like the shop has too. I hope you didn’t pay for all the guess work. Yes Larry, I do have an answer. I can’t promise you that it is the correct answer but it worked for me. The last “hair ball brake noise” that I choked on was due to a stress crack on one of the brake pad spreader clips. The clip was not obviously broken. The crack was nearly invisible. (Note the term “nearly”.)
With a fresh set of clips on the front calipers, no more noise. In case you wonder why the clips cured it, when you apply your brakes, the spreader clip moves outward and allows the pads to exert even pressure on the rotors. When you release the brakes, the “square cut seal” in the caliper bore and these clips help the pads move away from the rotor. When the clips are weak (or damaged) the pads can be just close enough to the rotor to vibrate at that annoying frequency that you were hearing. – MC
MC – Last issue we were resurrecting a 944 that had been stored for 10 years. The clutch was the next system to consider. On an older 944 the clutch system is fairly simple. Unfortunately, it is located in the front of the car sandwiched between the engine and the central torque tube. This makes access somewhat difficult and after 20 years, you could have a problem after you begin driving the car.
First, let’s take care of age issues that I consider routine maintenance. When you push the clutch pedal down, does it return by itself or do you have to pull it up with your foot? If it goes down but won’t come up, you might have fluid loss, mechanical binding, or an adjustment problem with the “over center” linkage adjustment. If it’s like most I’ve seen, though, it is likely a hydraulic problem.
The clutch hydraulic system receives its fluid supply from the brake master cylinder reservoir. Just like the brake system, rubber parts don’t age well. It is reasonable to expect, if the car is more than ten years old, that you will eventually need to replace both the clutch slave and clutch master cylinders. Since this is a budget job, though, we’ll see what we can do while spending very little money.
To get a look at the clutch master cylinder you will need to be a contortionist and screw your skinny little upper body up under the dash to look at the clutch master boot and linkage. If you find it wet or dripping, the clutch master cylinder will need to be replaced. If it is dry under there, you are in luck! You can wiggle your way out of the car and get underneath the car now. This is fun isn’t it!
Jack up the car, put it on jack stands and look at the side of the bell housing just forward of the starter. You should see a round 40mm rubber plug (or just an open hole where the plug used to be.) Pull the plug out carefully, you’ll want to re-use it later. Through that hole, you can view the action of the clutch slave cylinder while you have one of your buddies push the clutch pedal assuming that the clutch master is producing pressure. If it works, you are in luck…your system is producing some pressure. You should start by bleeding the system (see below) and then checking for proper disengagement. You will still need to plan on replacing the slave and master eventually, but you may be able to buy yourself a little time. Check again for leaks at the master after the bleed. The seal on the master may be deteriorated just to the point that it will hold pressure for a while, but leak down later. If you DON’T plan on performing the maintenance listed below for the slave cylinder, check it REALLY well for leaks after the bleed or you’ll be sorry later.
Even if the system will hold pressure, you can bet your bottom dollar that the innards of the cylinders are not in prime condition after the car has been sitting so long. Even if I was going to replace the slave later, I’d still want to try to clean it out, if only on principle. I would remove the clutch slave from the trans housing. On a bench, dismantle it and clean it well. If the bore is rusty or the rubber boots or seals are ugly, replace it. Typically, the slave cylinder lives only half as long as the clutch master cylinder which is not surprising considering the environment it lives in.
The other clutch components that should be serviced at this time are the clutch fork, pivot shaft, and bearings. In typical Porsche fashion, the pivot shaft runs on needle bearings. These bearings dry out since they are located inside the bell housing and get bombarded by clutch wear particulate. The shaft develops wear pockets where the needle bearings ride on it and between the dry bearings and pocketed shaft, the pedal can feel a little stiff and crunchy on an older 944 (and 911 as well).
You can remove the shaft and lubricate the needle bearings without major disassembly and this is a very smart thing to do. If you find that the shaft is not smooth and a little pocketed , you can gain another lifespan out of it by grinding another “flat” (where the set screw holds it in place) 180 degrees opposite the original flat. With this, the bearing rides on a fresh bearing surface. It only takes a couple of hours on average, and is well worth it in terms of both pedal feel and smooth actuation.
At this point with everything apart take a good look at the clutch and flywheel assembly and see if you can find any chunks of black rubber debris in the bell housing area. If you do, you might as well plan to replace the clutch since the clutch disc is “chunking”. (not a technical term) On many Porsche, the original clutch has a rubber center to dampen vibrations and eventually they fail. It you find no rubber parts, you win and you can start putting it back together.
So you have inspected all the parts, you have the shaft cleaned up, and the slave checked out. If you’re like me and want to maintain everything in beautiful shape, you’ll want to take this chance to clean and prep the bell housing area. The first word of caution is: Do not try to clean the internals with any spray cleaner. If you do, you can contaminate the clutch bearing or wash debris into the clutch. I use a long Q-tip with mineral spirits to clean the rubbing surface as best I can. The lubricant that I use for the bearings is a Wurth product called HSS-2000, a penetrating grease that sprays on with the consistency of WD-40. The carrier fluid evaporates and leaves the gooiest, stickiest grease I have ever seen. While the shaft and clutch slave are out of the car, you should spray some MolyKote dry lubricant on the rubbing surface of the clutch bearing, clutch “fingers” and the clutch bearing support. Now you’re ready to reinstall the slave, although you may want to take the time to clean off all the nuts and bolts, lube up the holes with anti-seize compound, that sort of thing…the next guy to take this apart will thank you, especially if it’s you!
Once everything is back together, you are ready to bleed the system. The first surprise is that when you push the clutch pedal down, it does not return. Remember the over center mechanism? This is the linkage designed to help you keep the clutch pedal down on the floor while you are at a stop light. You have to overcome this linkage and pull the pedal back up to continue your bleeding process. Try a piece of rope wrapped around the pedal.
After bleeding, the pedal should return on its own. If it does not, the mechanism may need adjustment or the master may not be able to hold a “prime”. Occasionally, in spite of your best efforts, you can get everything right and find that the master gulps in air when you release the pedal. Assuming it all works as expected, you have probably spent a full afternoon on this process. But, the clutch action should be silky smooth. If you’re lucky, you won’t have to do it again for years. Oh…and one last thing, if you want that 40mm rubber plug to stay in place, glue it in. MC
Q – Last month you gave me some great advice about how to get my 944 out of storage after ten years and now I wonder what else? Gino
A – Clearly having a running engine is number one and now the next process is resurrecting the brakes. In many cases, the brake pedal will be high and the brakes may actually function. Don’t trust them! They will fool you and after a few trips around the block, they may be smoking and barely stop the car.
The plan is to verify that the brake calipers are freely moving and that the pistons retract after extension. Remove the wheels and remove the pads, one caliper at a time. Have an assistant gently depress the brake pedal and watch the pistons move out. If they actually move, have him/her release the pedal to watch them retract ever so slightly. The pistons will often move out, even when they are stiff. If after ten years of the pistons function, you are truly blessed. If not, you will need to consider your options regarding the brake system in general. Consider the pads, inspect the caliper boots, slide mechanisms, try opening a bleeder valve, inspect the hoses, inspect the rotors (pretty rusty aren’t they) and with the pads out of the calipers, how do the rotors spin and how do the bearings feel.
If you want the brake system to work perfectly, all those things need to be serviced and If you drove your 944 for 10 years and it sat for another 10, every rubber part of the system is suspect. For instance, the internal rubber components of the calipers, ever if they work today, cannot work like new after 20 years. And the flex hoses, even if they look fine externally, they tend to swell internally and then they act as check valves. So after resurrecting your car, brakes are the next major system that will need to be addressed. Stay tuned for next month where we get into the clutch system. – MC
Q – When I start my 996 up in the morning I hear a sloshing noise in the right side of the car near the back seat. It sounds odd and passengers have commented about it. What is it? Terry
A – That gurgling that you hear is the oil in the tank getting heated up. I can’t explain why the noise goes away when the engine is hot, and I can’t understand why the engineers did not figure out a way to keep it from making that embarrassing noise. – MC