95C4VanIsle

I have a 95 C4 purchased last year (car currently has 43,000 miles) and have had no problems with the car until recently. After a recent oil change I noticed a tapping noise coming from the engine area. It is hard to describe but it is louder under the engine than from above and it sounds like tap.... tap,tap......tap..tap,tap......tap...tap etc.

The noise is not rhythmic as in tap..tap..tap..tap.. I took the car to an independent mechanic who seems to have a good reputation with other Porsche owners in the area. He said when he listened to the car he would also hear an occasional pinging sound which I have not heard. He said the ceramic portions of the exhaust valves may be a problem, the valve guides are probably going and said I would need a top end rebuild. The car is still at the mechanics shop 100 miles away so I really can't help any more with input on the situation as far as diagnostics go.

The only reference I found with regard to the tapping noise was one by Harvey Yancey "Adventures with a Top-End Rebuild". He found out that he had three bent valves which necessitated a rebuild. There were also several threads regarding "lifter noise" but I wouldn't know how to acoustically distinguish between lifter problems or bent valve problems.

I've searched the archives and most top end rebuilds are performed when oil consumption starts to increase or power is noticeably decreasing. I have put 8,000 miles on the car since I've had it, done annual oil changes (Mobil 1 5W-50) and only use a liter of oil every 2,000 miles. The car does not leak oil either.

I guess I am just concerned that the mechanic said straight away I would need a top end rebuild. If that is what it needs, so be it, but if there are other avenues to explore prior to dropping the engine for the rebuild ( ie. replacing lifters) it would seem prudent to explore them first.

Any advice would be appreciated.

Barney1

Get a second opinion, I think lifters... A bent valve would also give you a miss because of leaking compression.

95C4VanIsle

There are no competent mechanics close to me but I will be going over the MikeJ's in Vancouver in a couple of weeks. I'm sure he might have more of an idea what is wrong. I was hoping to drive with Mike to the Canada west meeting in Sun Peaks in a couple of weeks.

I will have to go back and get the car (100 miles and the return trip home) and then drive it over to Mike's (125 miles which includes an hour and a half ferry trip). Will this amount of driving hurt the car?

Thanks in advance.

Steve Weiner-Rennsport Systems

Bret,

A few thoughts,.....

1) Tapping sounds can be caused by many things including arcing plug wires, lifters, and valve issues. I would recommend a VERY thorough inspection and test of the entire ignition system to see if thats the culprit. Lifter noise is isolated by using a stethoscope (long handled screwdriver) placed on the valve covers to determine if thats the source.

2) Pull the distributor caps to ensure that the drive belt is intact.

3) Perform a leakdown test to check the general health of the engine taking careful note of where any leakage is coming from.

Hope this helps,

mike993c2s

It's hard to say unless you can actually inspect the valves or the guides visually. There was a ticking sound with my car almost 2 years back and I've had one mechanic tell me that it's the lifters..... so I went out and replaced all the lifters myself, but the sound did not go away. I took the car to another shop and they finally took the exhaust manifold off and found a piece of a valve guide missing! Ended up getting a top end rebuild and the car's been running smoothly ever since! Good luck with the 2nd opinion.

95C4VanIsle

Thanks for all the input, especially Steve. I think what I will do is actually ask the mechanic to do the leakdown to check the engine in general prior to doing any work. I would then be able to do the other things you mentioned Steve.

I still think I might get Mike to look at it as well prior to getting a rebuild at this point. His input would be invaluable. There are some other reputable Porsche repair people in Vancouver (Scan Automotive) that might be able to give better diagnostics and repair services as well.

Thanks for the help.

rconnon

Bret if it's any consolation, after changing my oil from M1 15W-50 to M1 5W-50 i also started to receive the exact same noise. Tapping noise that was NOT rhythmic with the RPM of the motor, its most noticeable between 1200 - 2000RPM... and with the car HOT

The only thing i can think is the change in motor oil - maybe i have a lifter on the way out and with the change in oil thickness i can hear it clearer now..

I plan on switching back to 15-50 to see if that makes a difference..

95C4VanIsle

Hi Rob,

I believe 5W 50 is what Mike put in the car last year which is the reason I stuck with the same oil weight. When adding oil over the winter I added 10W 30 but only a couple of liters during the 6,000 miles plus that I put on the car.

In my original post I described the sound as a tapping sound. On reflection it actually sounds more like an "arcing sound", definitely not a tapping sound. Is this the sound you are hearing? I'm not skilled in mechanics but I do believe I have heard the sounds of lifters going bad on other peoples cars and mine doesn't sound like that at all. If what my memory is telling me is correct, a lifter problem is truly more of a tapping sound.

Any other input?

Thanks

rconnon

i found it was really hard to isolate without pulling everything apart, my next project is replacing the ignition wires as they are original and the car has 90,000 miles now. It very well could be arcing as when the last oil change was done we also replaced the plugs.

Its soo hard to tell, the noise i hear is loud enough to hear while i'm in the drivers seat (while parked and noise reverbing from a wall) and if it was arcing i'd likely hear it at idle.. in my case it's 1200-2000 RPM.

95C4VanIsle

I can only hear mine when the car is at idle, and only when standing at the rear of the car. The snapping (arcing) sound is louder with the hood up. If I rev the engine the normal engine sound obscures the sound.

Doing further search, and talking to Mike, I will check out the possibility of arcing in the dark. Unfortunately I won't get the car back til Thursday to check it out.

I hope we both figure it out!

Mike J

Hi Bret,

A simple test for ignitiion arcs is to idle the the car in the total dark, pop the rear good and look underneath...often its not hard to see any arcing since it will spark like crazy in the dark. Also look around the coils (there is a pair, they are connected on the short leads from your distributor and mounted on the left rear of the engine) to see if you see any discharges, etc.

Given your low oil consumption and low mileage, I doubt its guides. Given you do not rev the hell out of your engine, I doubt if its a bent valve. It might be lifters, but if its sounds more like arcing it could be a bad spark plug wire.

Don't forget to lay by the car and look underneath when its idling. The lower spark plug wires towards the front of the car tend to have 180 degree bends which often cause the wires to crack as they get old.

We should also check your caps and rotors...I can't remember if we replaced them before?

Cheers,

Mike

Robin 993DX

Welcome to the ownership of an air cooled motor, they all tic and toc and rattle. Unless you are buring excessive motor oil I say save your money.

First thing to fail on the 993 motor would be the lifters, but when one fails you would know, it is loud sounds like you have a bad bearing. And frequency will change according to the RPM until about 2k rpm.

95C4VanIsle

It definetly is not a loud sound, like a bearing going bad and the frequency doesn't change. Hopefully I'll be able to get the car over to Mike's, have a look at the car, and schedule it for repair as I have that week off from work. Unfortunately I don't think I will be able to attend the Canada West Region PCA event in Sun Peaks which my wife and I had really looked forward to all year.

Once again, thanks for your input.

95C4VanIsle

I will be getting the car back from Nanimo on Thurday on the way back from Victoria and I will do as suggested. I'm definely leaning more towards the arcing possibilities.

According to the service records the distributor caps and rotors were replaced at the 30k service in Aug 2006 so I would think they would be OK. There is no mention of replacement of plug wires so I'll have to look into getting them replaced.

I'll try to PM you Thursday evening after looking for arcing. I'm actually hoping that is what is causing the problem.

Should I call Scan Automotive to try and schedule an appointment in a couple of weeks for an electrical inspecion of the car, or do you recommend someone else. Obviously I'd love to have you do the repairs needed if you had the time and inclination.

Thanks again Mike

Mike J

Bret,

You mentioned on the phone that its sporratic, and it does not appear to be syncronized with the rpm, right?

Cheers,

Mike