964 engine noise - please help

[TorqueHead]

I have a strange noise coming from the back end of my 92 C4 (non turbo).
The noise started yesterday.

This car had been in storage for about 15 years and I recently got it running. The noise appears to have started after the following service work I performed:

Replacement of distributor belt/installation of vent kit.
Change of oil/filter
New spark plugs
Setting valves (none were excessively loose or excessively tight)
Purge of fuel system and installed new fuel pump
Removed CAT and installed a gutted CAT.

Additional info:

Car has only 25,000 miles on it.

Previous owner had significantly overfilled the sump with oil. But now has the correct amount. Car was run briefly in the over-filled condition.

Car has never been driven since I purchased it.

Car has never been revved high since I got it running after its 15 year hibernation.

The car sat for several months after I got all the maintenance done and was then started up just yesterday and the noise was there almost immediately.

It is possible the noise has been there all along and was masked by the exhaust noises. As of yesterday when I first noticed the noise, there is no exhaust noise to mask engine noises because I have piped the exhaust out of my garage.

The noise sounded like it was coming from the AC pump so I removed the belt, but the noise is still there. I have included a video of the noise which was taken today, after the removal of the AC pump belt.

I checked for any interference between the fan and fan housing. I could not see any rub marks and an 0.008" feeler gage easily fit between all of the blades and the housing

I hope someone can give me some guidance.

https://youtu.be/nNM8E5zEwL4

[bazar01]

Tom, i watched and listened to your video clip.
It sound like it's coming from the alternator/fan bearing.
You can remove the fan/alternator belt and run it for a few seconds and see if the noise disappears.
Make sure you have a fully charged battery.

[bazar01]

This fan bearing can dry up and make a noise.

[bazar01]

[TorqueHead]

Thanks so much bazar01!
I sure hope it is something simple like that.
Cheers.

[TorqueHead]

Ok, so I got the alternator belt off. Do I have to remove the fan belt too?

Just using newbie logic here. If I put the alternator pulley back on without the belt and tighten the nut and then test run the engine, that should allow me to determine if the noise is coming from the alternator or if it is coming from the fan hub double bearing.

If I hear the noise then it has to be the fan hub double bearing right? Or am I missing something here?

[bazar01]

Leaving the fan belt should work.
If noise is still there, with the alternator shaft not turning, then it's the fan hub brg. Just make sure the pulleys are secured and tight.

[TorqueHead]

I think this is bad news. I may be in for a world of hurt...

With AC belt and Alternator belt removed, the noise was still there.
Next I removed the cooling fan belt and the &**%^$%$& noise was still there.

What could it be? I had the distributor out to do the upgrade- belt replacement and vent kit install.
I set the valves, but surely this is not a valve related noise??
I installed a cat bypass but I have looked for loose sheet metal and not found any?

Could this be timing chain related?

I really need some expert advice. This is my first Porsche. I have bought a ton of books including Adrian's Enthusiast's companion and Technical Data Without the Guesswork and I have researched various forums but there is no substitute for someone who has heard this noise before.

Even if you have not heard the noise before, I would appreciate your opinions and guidance.
Here is a video link to the noise with all belts removed.

https://youtu.be/WYkwrr6rP6c

[budge96]

Have you checked the level on the power steering fluid reservoir ? For the life of me sounds like the pump for the power steering running dry ..
Bert

[bazar01]

+1.
Got the fan and alternator eliminated.
Sounds like cavitation in the power steering pump .
Check that coz I don't think there's a major problem with your 25k mile engine.

Was the noise there when you started it the first time?

[TorqueHead]

Thanks guys,

I am not certain if the noise was there on the first start, which was mostly at idle. The noise seems to come after applying a bit of throttle. Also the noise (if it was there) would have been partially masked by the exhaust and by the fan noise, neither of which are at play now.
But thinking back, this new noise is pretty loud, so I would say it was probably not there on the first starts.

The power steering reservoir is low, but fluid is visible. It was leaking at the rack so I added some power steering stop leak. Could that be the cause? Should I top it off and try again?

If I recall what I read, removing the power steering belt is not an easy task.

[BLACK3.2]

Try filming a video while turning the steering wheel. See if that changes the sound.

I found this video of someone experiencing three exact same sound and it turned out to be the power steering pump:. https://www.porscheclubgb.com/forum/tm.aspx?m=992265

[bazar01]

Yes top it off to the mark. If the noise is still there, get an engine stethoscope and start probing.
You can plan on doing the rack reseal later but try to enjoy driving the car first once you got the noise issue resolved. Just keep an eye on the reservoir. You got most of the important maintenance items done anyway.

Once I had to remove the power steering belt and pulley and cover to replace an engine oil leak at the camshaft ps pump seal. Not a fun job. But my 1993 has already 74k miles and used to have a lot of oil leaks when I got it. Now it's dry.

If the reservoir fluid level is visible, there should not be pump cavitation then. Not sure if there is a screen in the bottom of the reservoir. Sometimes they clog up and cause pump cavitation. May need to research the filter to make sure or just flush the stop leak and old fluid and pull the reservoir and clean it.

What is the oil pressure at idle when cold?

[TorqueHead]

Black3.2 - that video clip does sound a lot like my noise! I will try the steering wheel trick on the next startup.

Bazar01 - Yes I would love to enjoy the car for a bit before dealing with a rather slow rack leak!
I think I will pump out the reservoir, remove it, and clean the screen. I will also try the stethoscope as you suggested. Oil pressure is 4 on the scale of 5 so I assume that's good?

I appreciate all the help guys. This is a rather nerve-racking experience and it sure helps to have this support. I will keep at it, and keep you posted.

[TorqueHead]

I did not have much time yesterday to work on the car, but I did start on removal of the power steering reservoir and quickly ran into issues. The top hose which I understand is the supply hose is crimped to the reservoir but the other end of it goes to the pump and that had a hose clamp which I undid and the hose came off fairly easily. So far so good.

However the return line is the opposite arrangement; it is permanently attached to the end that goes to the rack and the end that goes to the reservoir has a hose clamp. I got the hose clamp undone, but cannot pull the hose off the reservoir. I can barely get at it because the crimped supply line is directly above it. I have tried pulling on the hose with my hands but am afraid of snapping off the plastic stub from the reservoir if I pull too hard or pull at an angle. I have tried some gently prying with a screwdriver. I have loosened the reservoir but it won't move far due to the connected hose so that was not much help.

Today I am thinking maybe if I warm up the hose with a heat gun it might expand/soften the rubber enough to help it slide off.

[TorqueHead]

Also my research indicates the reservoir does have a non-removable screen, but I should be able to back flush it and inspect it when I get it on the workbench. Otherwise I have to get a new reservoir in order to get a new screen.

[TorqueHead]

Quick update of last two days and then some stunning news.

I was able to remove the reservoir and back flushed and forward flushed multiple times with varsol.
From the very first flush, it flowed really well and all the flushing did not produce any dirt so we can rule out the reservoir screen/filter as a cause.

One thing to keep in mind is that when pumping out the reservoir, I found the fluid to be very thick, possibly due to my use of Lucas stop leak and the fact that my garage was at around 12C.

I was just about to re-assemble and continue with a steering fluid flush when I thought I would take a peek inside the pump with an inspection camera. I was NOT prepared for what I found. To be continued on next message with photos.

[TorqueHead]

With the supply line to the pump disconnected, I slid an inspection camera in there to take a quick look. The photos below, show my setup where you can see the flexible camera lead going into the pump and shows what I saw on the camera.

I apologize for the poor quality, but it is a picture of what was displayed on my handheld inspection camera so there is some loss in resolution.

[bazar01]

Can't see it clearly on my phone screen. What is it you were not prepared to see?

[TorqueHead]

Hi bazar, I got the same complaint from another person. I have annotated the picture and have included it here but in case you still cannot see it clearly, I will explain. I am seeing what looks like a mangled O ring. It is shiny, black and looks about the right size for an O ring although it may not be round in cross section. It could be rectangular.

Seeing as it is on the suction side of the pump, where in the heck did that come from?
It almost looks like the sealing rings that come with a pump rebuild kit but I am stumped as to how these could become dislodged inside the pump.