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Join Date: Feb 2004
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1986 Porsche 944

MOTOR VIBRATION........

Good day to everyone.

I bought a 944 with high miles 149k.

The good:
Motor seems strong.
Shifts good.
Breaks good.
Electrics and charging system good.
Suspension tight.
Great oil pressure 40-50 lbs.

The bad:
Motor was noisy.
Motor front seal leaked.
Balance shaft seals leaked.

Repairs that I did:
Motor noisy: replaced the timing belt and balance shaft belt; tension set without a tension gauge, motor quite now.
Motor front seal: replaced
Balance shaft seals: replaced
Set timing for motor and balance shaft per Clark's repair manual online

The motor is noisy when idling (vibration)

Could this be motor mounts?
What do you think?

Jim

PS. Should I have used the directional seals for the balance shafts?


Last edited by jimpen; 04-23-2018 at 05:17 PM..
Old 04-23-2018, 12:45 PM
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If it is vibrating at idle and tends to smooth out when you give it gas, then most likely motor mounts.

If the vibration continues or gets worse with higher RPM's, then the balance shaft alignment may be off. I had to do this a couple of times before getting it right the first time I did the belt job.
Old 04-23-2018, 07:02 PM
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Quote:
Originally Posted by RedCarGuy View Post
If it is vibrating at idle and tends to smooth out when you give it gas, then most likely motor mounts.

If the vibration continues or gets worse with higher RPM's, then the balance shaft alignment may be off. I had to do this a couple of times before getting it right the first time I did the belt job.
Thank you. What mounts are the best? Jim
Old 04-24-2018, 07:23 AM
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It looks as if the lower balance shaft seal may be leaking. I replaced the all recently.

Are there any good/best seals around to stop the leak?

Thank you, Jim
Old 04-24-2018, 07:25 AM
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Is the oil pressure OK at 40-50 lbs?

Thx, Jim
Old 04-24-2018, 07:27 AM
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Disclaimer: I can't comment on long-term durability, but I suggest to get the cheap motor mounts, the same suppliers make them all.

Is that oil pressure cold or at operating temperature? That's about 3 bar, which is good for a warm engine. What oil are you using? It is strongly recommended to use a high-zinc 20W-50 for warm climates.
Old 04-24-2018, 09:12 AM
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I am using Mobil 1 10W40 High mileage synthetic oil.

The oil pressure with a cold engine is closer to 50 psi. When hot it stays at 40 psi.

Thanks for the information on the motor mounts.

Jim
Old 04-24-2018, 10:06 AM
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Don't use/buy the cheap motor mounts - the Porsche mounts are the only ones that are hydraulic, they are expensive but they will last MUCH longer. The cheap mounts are just rubber and metal, they will wear out quickly. Read this first hand experience for more info.

Last edited by 944fan2018; 04-25-2018 at 12:12 PM..
Old 04-24-2018, 12:03 PM
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My experience with aftermarket motor mounts has been consistently miserable. Its one of the components on a 944 that for me, must be OE. Id rather put a used original that measures to spec rather than go aftermarket. YMMV.
Old 04-24-2018, 07:10 PM
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I had the same experience with my 59k 1984 model regarding the vibration. Did full engine service and it ran fine but at idle it would vibrate the interior plastics. Off idle was fine but it was so annoying to be in a pristine low mile classic sports car that I felt like I had to make excuses for. So I replaced the motor mounts and that proved to be the issue. I used the $38 Meyles from Pelican with good results. I understand they may not be up to OEM standards, but $500 for a pair of pedestrian motor mounts from Porsche seemed crazy to me. It's not rocket science to make a set of molded rubber bits with threaded mounts and a metal bracket.

Someone asked an important question about the vibration. Does it continue at higher RPMs? For setting the balance shaft and timing belts, there is a guy on YouTube who's work was stellar. I cannot recall his name but on my thread about this within the last year, I specifically praised him and identified him as a great video choice. You might watch his video and decide if you got this down, or missed a detail or two. Just search on my name - others here recommended this guy.
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84 944, 87 Vanagon, 88 Mitsubishi Van Wagon, 88 Supra Targa, 1990 Audi 90 20V Quattro sedan, 1992 Lexus LS400, 1993 LandCruiser, 1997 LandCruiser, 2017 Subaru Outback.
Old 04-24-2018, 08:46 PM
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OK, I put in new motor mounts (Meyle). The fit is good and they did away with the engine vibration.

While running the engine, the throttle body started to stick. I tried oil but that did not help. So, I pulled it off and took it apart to see if the sleeve/bearing was bad. I found that one of the roller bearings was almost seized. So, I got my hands on a used one in good condition and installed it. It seems to work OK except the idle is at 1400RPM.

Any suggestions?

Next question, do I need to let excess air out of the cooling system, if I remove the radiator and drain the cooling system? I noticed that there is a bleed valve on top of one of the radiator hose connections to the engine.

Thanks, Jim
Old 05-18-2018, 12:57 PM
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Carefully check (with proper procedure) those balance shaft alighnment notches again...especially the bottom one - easy to get this backward without very explicit directions.

Doug...might you be referring to Van Swenson?
Old 05-20-2018, 05:10 AM
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Quote:
Originally Posted by OK-944 View Post
Carefully check (with proper procedure) those balance shaft alighnment notches again...especially the bottom one - easy to get this backward without very explicit directions.

Doug...might you be referring to Van Swenson?
Double checked the belts, they are good thanks.........
Old 05-20-2018, 07:16 AM
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For the issues with high idle...

If this was a used TB, are you sure the seals are good? Replacement seals and O ring kit is under $30, and the work effort is not bad.
Double and tripple check the TPS is properly positioned to measure closed throttle condition. I screwed this up twice.
Follow Clarks /factory procedure for adjusting idle with the screw on top of the Throttle body.

Old 05-20-2018, 08:32 AM
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