Difficult to change spark plugs in C4??

Can this be done on a C4 with 12 plugs with the use of exotic or special tools??

I don't think it requires any "exotic" tools, but you do have to take a section of the exhaust off to get to all of the lower six plugs .

It's easy to do the plugs once you get a few things out of the way - as Bill said. While you've got all that stuff off, you might as well do your valve adjustment - if you haven't already done them yourself yet. You have to drop the exhaust to get to the bottom plugs anyway - you're only a heat shield and a valve cover away from the valves. On the top, you've got to lose the heater blower on the left, the air filter housing on the right, then you're at valve covers up there. Kind of a pain in the back getting to the last ones on the top - but well worth the savings over dealer cost of getting to it.

Thanks for the tips. I have not yet done a valve adjustment on a Porsche, though I have done so on a variety of other engines. Is there a reference that you would recommend? I have only the Hyanes manual so far. Is the tech article on the subject of valve adjustment applicable to the 3.6?

When you said "drop the exhaust," did you mean only the heat shielding, or did you mean the muffler & pipes as well??

Originally posted by ServerDude:
It's easy to do the plugs once you get a few things out of the way - as Bill said. While you've got all that stuff off, you might as well do your valve adjustment - if you haven't already done them yourself yet. You have to drop the exhaust to get to the bottom plugs anyway - you're only a heat shield and a valve cover away from the valves. On the top, you've got to lose the heater blower on the left, the air filter housing on the right, then you're at valve covers up there. Kind of a pain in the back getting to the last ones on the top - but well worth the savings over dealer cost of getting to it.

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Steve
'89 C4

The Tech Article on Pelican is very mappable to the 964. I just finished mine this weekend and was thinking about writing up an article to be more 964-centric. I'll keep you posted.

I say, start from above. Get the heater blower and pipes out of there, then disconnect and shove the O2 sensor wire through to below. The right side is easy - just remove the airbox. It helps to have the fuel line removed, but you might not want that open while working. This is also a great time to replace the fuel filter. It is a hard reach under the power steering pump, but manageable - don't mess with it.

For the bottom - drop the undertray and stow neatly in the back corner of your garage never to be used again. (That's my opinion anyway.) For the exhaust, you can leave the primary muffler - the one under the bumper cover be. It is strapped in place and is fine where it is. the catalytic converter and secondary muffler have to go though. Four bolts on the catalytic converter and another one on the round clamp headed to the muffler and it is gone. The secondary muffler on the passenger side is two bolts and the clamp. It weighs a good bit so be ready to hold it. Under the muffler/cat you've got a heat shield each, and you're home free.

Re-installation is best from ground up - but I only say this because I kept forgetting about that O2 wire which is not possible to reconnect with the heater blower in place and a wrist greater than 1/2" in diameter.

No matter how many times I do the adjustment, I'm always amazed at how wonderful a finely tuned 911 engine is. My favorite two times of the year are the test drives immediately following my valve adjustments.

Good luck!

ServerDude wrote:

"For the bottom - drop the undertray and stow neatly in the back corner of your garage never to be used again. (That's my opinion anyway.)"

...and good advice it is!

According to Steve Weiner (hope I got the name right) of Rennsport, a fair number of the problems encountered with the cylinder head leakage found on '89 through early '91 production models were heat related. He implied that if the tray is removed the cooling improves greatly and it can help reduce/eliminate the problem. I don't need to really worry about this (I think...but I'll probably take it off anyway) since I have a '91 C4 with the factory installed cylinder fixes, but the primary reason for that part is to reduce noise to some type of Euro-spec, noise levels and help the aerodynamics of the car at very high, Autobahn-like speeds....neither of which apply to us in the U.S. .

Just thought I'd throw that in.

Bill Wagner

The only "good" thing I found with the undertray is that when you parked at a friend's house for a few hours - it caught the oil before leaving a signature on their driveway.

Regarding Bill's comment: "problems encountered with the cylinder head leakage found on '89 through early '91 production models"

Exactly what kind of "leakage" are we talking about here? It almost sounds like oil leakage due to thermal warpage of the head?? I'm presently puzzling over oil leakage on the garage floor, as well as "lugging" noise in low rpms. I'm hoping a valve adjustment (which I now plan to do this weekend for the first time) will cure the "lugging" noise, but while I'm working I'll be looking for oil leaks. Any checklist on where to find the pesky oil leaks? Also, any recommendations on plugs, wires, etc.?

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Steve
'89 C4

Serverdude: Do you recommend that the catalytic converter gasket and the muffler exhaust doughnut be replaced??

I never change the muffler doughnut ring. I get my valve cover gasket kits from Vertex Auto and it has 4 new bolts for the catalytic converter and the gasket for the cat, but the others seem to reuse pretty well.

I know there are a few articles on valve adjustments for other models but I haven't seen one specific to the 964's - so I wrote one. If you want to take a peek and (hopefully) give me some thoughts as to if I missed something or did anything wrong, I'd definitely appreciate it. It's on my web page. I just wrote it today so I haven't proofed it too many times yet. I also want to take some pictures during the next one to show some better illustrations. I tried to keep it simple and cover all the questions I had when learning mine. Hope it doesn't sound too simple.

Plugs I use are Bosch Super 3-node copper (FR5DTC) and are about $4.50 a peice. I haven't replaced the plug wires. Can't see spending that much on wires unless they are truly degraded. I also just switched to Mobil 1 on this last oil change. Even with close to 120k on the clock - didn't notice any extra "leakage" caused by synthetics. I'll keep you posted.

Brian



[This message has been edited by ServerDude (edited 02-22-2001).]

As far as your oil leakage goes, I wouldn't panic. It could be a lot of things. Keep in mind these cars aren't exactly new and it's normal for cars to develop leaks with age and mileage. It could be an oil leak from a valve cover gasket, oil lines, seals, etc. etc. If you drop your tray off and a ton of oil comes pouring out of it, then you probably have a serious problem of some type, but who knows how long it's been building up? Is your oil consumption high?

The early C2/C4s didn't have head gaskets and relied on a tight metal to metal seal to prevent oil leakage. When exposed to heat, some cars would indeed apparently cause the studs to distort hence causing the leak to occur. The fixes are to either replace the cylinders and pistons with new updated ones with the cylinders using a gasket, or have the heads re-machined. One of the owners of a local shop told me that if the car develops this problem the leaks are BAD, and they usually occured between 20K and 50K miles. If you do have this problem, I believe the leak will show up where the cylinder meets the engine block.

I've looked at a LOT of 964s, and I've never seen one that was a hard core leaker (Bruce Anderson implied the problem isn't that severe or common in his PORSCHE 911 PERFORMANCE HANDBOOK). I have seen a fair number of 964s develop minor leaks for other reasons (oil lines, seals, gaskets, etc.) and I just attribute it to age and/or mileage. I've never seen a car with oil pouring out of it because of the cylinder problem. It's difficult to really determine how serious this problem is or was. I find it VERY hard to believe that every single car I've looked at has had it's engine semi-overhauled with no documentation of it at all, and I know of a fair number of people who own 964s that have gone well over 100K without any leakage problems at all....but I have encountered a fair number of cars approaching 100k miles that DID need some seal work done.

As far as your lugging noise goes, I can't help you except to tell you that the owners manual says not to lug the engine (not that I'm implying you're doing that). I can't hear your lugging noise from here, but it sounds more like a transaxle problem rather than a motor problem. The oil leaks MAY be from other sources as well (like the transmission, and the power steering pump which is a known leaker). While your at it, check ALL the fluid levels in the engine, transaxle, and diffs.

How many miles are on your car?

Bill Wagner
91 C4, 18,700 miles

Brian's valve adjustment procedure article is EXCELLENT! Nice job, Brian, and thanks for giving me the confidence to press forward on my first adjustment. I'll let you know how it turns out.

Bill: Thanks for the historical background brief. My car has 38,500 miles. I have been on my back with it up on ramps while idling and definitely do not have a gusher anywhere!! I don't think it is the valve covers, and I don't think it is the return tubes. However, the leak does seem to have gotten worse over the past six months. Possibly, I'm just more sensitive to it because I'm driving it a lot more than I used to. I don't think I'm consuming much oil at all - I think most of what I "use" is just leaked. I'll give it a good hard look this weekend, and will hopefully find the source(s).

I think you are correct about my "lugging" noise coming from the transaxle or differential. Can you advise me on the checks I should make, point by point (I'm trying to locate some factory manuals, but still don't have good documentation.)

Thanks to you both.

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Steve
'89 C4

An often over looked source of leaks is the forward end of the right cam where the power steering pump drive is.

sms1305:

I wish I could give you a point by point description of how to check stuff out, but I just got my car a month ago after researching them for about a year and a half, and I CAN'T FIND ANY MANUALS ANYWHERE!!!

Do you know of a source? Currently the only resource I have is from www.alldata.com (better than nothing!) but it tends to be limited to fairly simple maintenance and repair items. It DOES, however, have all the TSBs for the car. If you have nothing else, you can subscribe to it for $20/year. Not great, but it's better than nothing. At this point about the only thing I could tell you is to make sure you do have oil in the transaxle and diffs...if that was the source of your leak it would certainly explain the lugging noise.

Good Luck,

Bill Wagner.

P.S. If you know of a source for the manuals, please let me know, and I'll be happy to do the same for you!

Serverdude: I used your article to the letter. It was superbly organized and easy to follow. I only got stuck on one minor point. After I got the car up in the air, I forgot to put it back in neutral. Thus, when I attempted to rotate the crank via the fan pulley, I got no movement! After going through the belt tightening process several times, I finally realized my stupid mistake.
My second thought is that you might want to add the suggestion of doing a quick compression test after the valve train is adjusted. Maybe it's just habit, but I couldn't close everything up not knowing what my compression numbers were. It took too long to get there. It took only minutes to satisfy my curiosity. Anyway, I give your article two thumbs up. Thanks.

Bill: Regarding manuals, I found a source on ebay that has many auctions for a variety of tech manuals for different cars. He's auctioning off a complete microfische manual set for the 89-94 C2/C4's. I e-mailed him asking if he had a paper copy or other microfische copies that he would be willing to sell. Although he didn't have a paper copy of the books, he said he had extra sets of microfische. Anyway, we settled on a total of $32.50 for the set (including shipping), and it's in the mail already. The current bid on that set is now at $42.00! If you're interested, his ebay name is "ranbye," and like I said before, he has a bunch of on-going auctions, and many positive endorsements. I don't know if this will work, but try: http://cgi6.ebay.com/ebaymotors/aw-cgi/eBayISAPI.dll?ViewListedItems&userid=ranbye
for a listing of his items. I'll let you know if the goods are delivered as promised. Thanks for your help.

Interesting to read through the messages for the valve adjustment. Very informative. At what frequency do you adjust the valves on a C-4. I drive my 911 approx. 3,000 miles a year. Thank you for your recommendation. Jim V.

James:

It depends on the year. Some of the specs Porsche put out get a little confusing, as some say every 12,000 miles, and others say every 15,000 miles. You also need to get the brake fluid changed every 2 years, which, believe it or not, is apparently VERY critical as the ABS system tends to be hard on it. It's function is not limited to the ABS either, I think it's tied into the AWD system and the clutch.

As I said before, I still need manuals so verify everything I'm saying with a Porsche shop.

Good Luck,

Bill Wagner

Thanks for the excellent feedback. (If you like this article, you should read my book on Windows 2000. Sorry, gratuitous plug.) Hey, I've never done a compression test. Could you give me a run down on it? I'll do a search here as well.

Valve adjustment frequency: You find every recommendation under the sun here from the die hard 30,000 milers to the people who do it every oil change. I think the most prevalent is on the once or twice a year routine. Now that I have been doing it myself, I go for twice a year. The cost is much easier to swallow when doing it yourself as opposed to having a dealer adjust them. But I put a LOT of miles on in a year. Even though you're only driving 3000 a year, I'd still do the adjustment yearly. Also, listen for the 'ticking' valve train. It is the best indicator of loose. Too bad the tight yet silent valves are the really dangerous ones.

Thanks again for the comments, and I'll add a note on putting it in neutral.
Brian
'91 C2

What brand of valve gauge do you recommend? In your article you mentioned purchasing a new more expensive gauge for the next valve adjustment. From your article I will be attempting to adjust the valves...sometime this summer. Jim V.

The metric dial gauge at Pelican is listed with a price as NA, so I don't know what is up with that one. You will need the Z-block, but I believe that many people get metric dial gauges from Sears or the like. Can't say too much as I've never done it this way yet. I'll do another adjustment in the fall probably and will get a gauge by then. I'll let you know when I update the instructions.

So glad to hear people doing this adjustment themselves. It really is easy - as long as you don't mind spending some time in the garage with your Porsche... like any of us would.