New here, Question on a strange noise from the engine
 

Hi everyone,

I picked up my '86 944 w/ 43k miles about a month ago. In that time, I've performed all of the preliminary maintenance (flushed/bleed coolant system, replaced DME relay, new plugs, oil/filter, etc.) and am now preparing for some bigger projects; first up will be the timing/balance shaft belts and rollers. It's been 10 years since they were replaced (the car sat in storage for most of it's life).

Before I do that job, I'm trying to make sure everything else relating to it is up to snuff. My next investigation involves a strange rattling noise that occurs above 2200 RPMs. In the video below, you can clearly hear it come in and taper off and is consistent with the RPMs. There's also some very noticeable belt whine, but from what I understand that appears to be normal.

Any ideas on what this could be from? It does appear to be "in" the engine.

https://youtu.be/VZ9TrIMi-CA

Thanks!

I don't recommend running the engine any longer until you've done the belts. That whine is from a balance belt that is way too tight. Because of it's age, if it breaks, it can easily break the "old" timing belt and wipe out your valves. While you're in there (WYIT) I recommend replacing the water pump and any seals that are leaking on the front of the engine. There's a lot of other items that you might consider, due to it's age and sitting for so long: Throttle body shaft "O" rings, Vacuum lines (silicone ones), Tires (they shouldn't be over 6 years old) and fuel filter. Also pull the battery and see if the floor of the battery compartment is rusted through. If it is, it'll leak water into the DME. The other stuff will present themselves through time.

First off, welcome! And congrats on finding a low mileage example.

"The other stuff will present themselves through time." (so true, these cars are very possessive of your time.)

Thanks for the warm welcome! I was able to solve the rattling in the video; the idle control valve was vibrating. Thankfully nothing major.

As for the belts, I'm shopping around now for a good deal. I'll be replacing the rollers too. Is it true that Gates and the OE belts are the way to go? And my water pump was replaced by the P.O. 2k miles/10 years ago, would it be safe to assume it's still ok if I haven't had any leaks or other issues with it?

I would venture that the WP's probably going to be ok. I'm just a believer of "while you're in there". I believe the Gates or Conti belts are fine but remember to re-tension after around 1500 miles. By the way...congrats on getting what most of us believe is a great car.

Ok good to know, thanks! And yes seems like retensioning is just as important as replacing the belt in the first place. I'm going to be ordering a set of the arnnworx tools to complete that job. Otherwise, fuel pump, fuel filter, and oil gasket have been replaced. No leaks of any sort that I can find so far. Just idles a little rough for a moment when she starts cold, but adjusting the idle speed did help.

It's been a joy to own so far. Makes me happy just looking at it! It's my first Porsche and just going through it and seeing the attention to detail and quality of the vehicle, even at 30 years old, is astounding.

One other unrelated question; when I got the car, the oil pressure gauge was always "pegged" as soon as the ignition was turned on. I identified an open circuit in the oil pressure sending unit and replaced it with a new one from Bosch. Now the pressure reads properly, but it's always sitting around 5 bar when driving. If it's been (really) warmed up and driven for about half an hour, it will bounce to between 3 and 4 while idling, then go right back to 5 when you start moving again. I'm running Valvoline VR1 20W-50 and that's a pretty thick oil but does this sound normal to you guys, pressure wise? I've been fearing it could be related to the pressure relief valve, and I have the old style so it's pretty expensive to replace.

oil pressure usually gets pegged at 5 when cold cause the oil is so much thicker when cold, but normal pressure is between 2.5-4 mine usually moves up to 4.5 when driving hard. I drive with brad penn 20w/50

Thanks Alex, that leads me to think there may be something wrong then with my constant high pressure. Would the oil pressure relief valve be effecting this?

The only other oil besides the great VR-1... that I would recommend would be Valvoline Harley Davison (Motor Cycle 20W-50 Oil)... cause it has a high temp. break down point by about 40-60 degs. higher than the VR-1 and that little bitty tinny wiener stock (OEM) oil cooler is just not getting the job done when you are running in a DE or Racing Class on hot 85+ Deg. days. +++ here... it also has a lot more additives that helps with the coating of all the moving parts better the VR-1 (SAE)has. AND... it's about a $1 cheaper per QT> than the VR-1!!!!!!!!!!!!!!!!!!!!!
JMHO.... when it come to oil pressure and keeping your high $ engine together!
Ron

I appreciate that info, RR. I'm going to order some of the Valvoline HD as I'm now in need of fresh oil. I've got another active thread on here where I'm troubleshooting an oil cooler seal and I just flushed out my milkshaked VR1.

Ain't it the truth! All the "stuff" so far seems to be related too (overheating, losing coolant/gaining oil, now leaking OC seals). Come to think of it, the only thing that hasn't been related to my other issues was this rattling noise I originally posted about, go figure!

Rattle... "Rattle... Boom-Boom... Bang"... that rattle noise is more than likely the heat shield by the turbo short exhaust exit down pipe to the main (3) bolt down pipe ... take a long screwdriver and pry it away from the turbo short down pipe and (3) bolt down pipe the rev. the engine back and forth to idle and see if it goes away?
Ron...

His car is an N/A.