PortlandTom

Well, I talked to Blackstone Labs, and they can tell if the oil overheated or if a bearing is failing. So I'm going to send in an oil sample for analysis. That should give me a good indication of how to proceed.

Assuming the problem is overheating oil, I'm going to replace the oil thermostat spring, as it sounds pretty simple. In the diagram below, is it part # 42 or 44 that gets replaced? Or both? And are parts 32-39 involved with oil pressure or cooling? Should I replace those springs as well?

I'm also thinking of checking over the rest of the oil cooling system. Can a radiator shop check the cooler to see if it's flowing properly?

Finally, is there a simple place to plumb in an oil temperature sensor? That could be handy if the problem turns out to be overheating.

Thanks,
Tom

Chris

You need to replace 42, 43 and 44.

Chris

mark kibort

could the pressure regulator also be a possibliity? (#33 spring)

Interesting,if you dont have the oil cooler, you dont install any of those components. 42-43 and 44 are removed and the stuff around spring 33. I can understand the cooler associated components, but why are the pressure regulator gysmos removed? how does that system keep pressure regulated?

mk

Chris

33 is not used with the external oil cooler, it is just there to prevent excess pressure from reaching the 'weak' cooler in the radiator.

PortlandTom

I got the oil analysis back (posted below). I talked to a guy at Blackstone and he said that a difference between zinc and magnesium of more than 200 ppm. indicates overheating. He also said the wear is above average, but nothing to worry about. So I'm proceeding on the assumption that it's oil overheating, not a bearing or something major like that.

I also got the thermostat replacement parts and have started installing them. I got the oil pressure sensor off, but the thermostat cover doesn't want to budge. I even used a 2' breaker bar, but no luck. I'm soaking it with Liquid Wrench and tomorrow, I'm going to try rapid heating and cooling to break it free. Any other tips on getting it off? I'm afraid of using too much force since it's threaded directly into the block.

I also took off the oil cooler. It had quite a bit of dirt on the forward face. I cleaned that out as much as I could and took it to the local radiator shop to have it tested to see if it flows OK. Hopefully these steps will keep my oil nice and cool.

Tom

Chuck Schreiber

Tom,

Tell me if you figure out how to loosen that up. When I did the 79 sending unit, that was all I could get off. The cover (housing above it) that you are referring to, I could NOT get off no matter how much brute force I put on it, so I just ended up replacing the sending unit and that was it.

wds928

Here is my oil analysis from about 2 months ago. I use Mobil 1 15w/50. Miles on the motor is now 149k and I just ran an autoX a couple of days ago, with no issues.

Porsche oil analysis no header 4-2008.pdf

heinrich

When Keith called me to discuss this issue of yours Tom, 2/6 failure was my thought as well. My first thought was oil overheat, but since Keith assured me your tems had remained normal, I ruled that out. Your oil analysis does not lead me to believe you have bearing failure.

PortlandTom

Well, I got the thermostat cap off yesterday. Repeated healing and cooling did the trick. I used a heat gun and freon spray from Radio Shack. It took a lot of patience, because of all the thermal mass to heat and cool. After two cycles, it broke free using a 2' breaker bar. And the threads on the cap and on the block show no damage at all.

So Monday I'll get the oil cooler back, and assuming they don't find any problems with it, I'll put the car back on the road and see if the problem is gone.

I did notice one strange thing, however. Parts 32-35 on the PET diagram (posted above) seem to be missing on my engine. On the picture below, the two threaded holes just below the split in the crankcase are for the oil cooler hoses. Just above that and to the left is part #39. To its right is the hole where parts 32-35 should be. Instead, there's just an unthreaded hole. Were these parts deleted for the GTS? What are they for anyway?

thanks,
Tom

P.S.

wds928: Thanks for the copy of your oil analysis. It was interesting to compare it with mine.

PortlandTom

I should have reread Chris's post before I posted. So parts 32-35 protect the oil cooler. Did they strenghten the oil cooler for the GTS? Or just decide they weren't really necessary? And what do parts 36-39 do?

Tom

callgeorge

Whenever I idle or drive slowly uphill, above warning comes on; reading of oil pressure is about 1 bar and vehicle idles roughly, then when I increase rpm on more level surface, oil pressure is 5 bar and signal disappears; I have replaced what appeared to be low oil(usually burns 1 quart per 1000 miles) but do not want to overfill--dipstick does not have markings but is 3inches full from bottom of dipstick; I have been religious about oil changes; something about reading is positional--I do not think more oil will cure reading above. Please advise...

dr bob

George--

Your dipstick has oil level hash on it, and a twist in it at the high- and low-level marks. If it's for a...

What kind of car did you say you have, and what year?


... S4+, the markings are pretty obvious. If it's an earlier car, 16V, the markings are pretty obvious. So get the correct dipstick, and confirm the oil level is OK. What oil are you using? The owner's manual tells you what to use based on ambient temps range. 10W-40 covers a lot. I use 15W-50 Mobil-1 in our warm SoCal climate. Maybe an oil change, with the correct oil, adding the correct quantity, will help the problem. If nothing else it will help rule out the oil and the level as possible causes. Save a clean sample of the old oil for analysis in case new oil doesn't help directly.

Rich9928p

On 11/30/2008 I posted a thread regarding cam chain tensioner replacement on my '87 S4.

See:

https://rennlist.com/forums/928-foru...alve-only.html

When the cam covers were removed we discovered that one of the plugs that cap-off the rear oil passages had fallen into the engine. Even since I had purchased my '87 I noticed the oil pressure was about .5 to 1 bar lower than my 928GTS. As part of the cam chain - cam tensioner replacement he rubber caps were replaced by newer pins to plug the oil passages and the oil pressure is back to where it should be.

What I don't know is if the GTS also had the rubber plugs in the back of the heads or if the newer pins were installed.

This could be a cause of lower oil pressure in any of the 1987 and newer 928s (that have the shorter cams) that use the rubber plugs.

Rob Edwards

GTS heads ('93, anyway) still have the rear rubber plugs.

EDIT: crap, now I'm not sure. Found this pic from when I was disassembling, showing pins but no rubber plugs. There was no evidence the valve covers had ever been off, but then you sure wouldn't have known anyone had been into the rod bearings either....

callgeorge

Yes, I have 93 GTS; recently had intake manifold job done; valve covers were replaced at this time.