Bondospecial

At the beginning of July I picked up a 176k mile 86.5 automatic 928S that had been sitting since 2001. I am mechanically experienced with old American V8 engine rebuilds, some american automatic trans builds, and EFI conversions on American stuff but I am a newcomer to these cars.

I got the 928S running with a new fuel pump and filter and a flush of the fuel tank, and it seemed to run smooth, but I did not drive it off my street because it immediately was evident the water pump had a huge leak. Since I had been cautioned that I should not drive the car at all on the very old timing belt I figured a timing belt, tensioner, and water pump job plus plugs, wires, oil change, etc should put this car in a condition where it was at least safe to run so I could shake down the other systems.

Other problems I found upfront with the car:

-The coolant that was in the engine when I got the car was a milkshake, and very oily, but the engine oil that came in the engine when I got the car was very clean, and only about half a quart low. The milkshake coolant seemed to have a combustion gas/old nasty engine oil smell to it but I wasn't 100% sure on that.

-The automatic trans did not power the car when I initially got it running, and I found the trans was nearly a gallon low but had no visible leaks. I filled the trans correctly, while running, and then a short test drive up and down the street revealed it seemed to shift great.

My diagnosis at that point based on the very low trans fluid and the milky coolant, but not milky engine oil, was that the internal trans cooler in the radiator must have failed, so I bought an all-aluminum 4 cooler 928S radiator and planned on replacing that concurrent with the timing belt, tensioner, and water pump job.

Well I just finished the timing belt, Porkensioner and water pump job, and I verified the cam timing marks continued to line up at TDC as I rotated the engine over multiple times by hand, so I decided to do a compression check since I had the plugs out already, before I put them in and buttoned the car back up to hear it run again (at which point I would celebrate how smart I was). But Oh boy:

BAD news on the cranking compression check.

Driver's side head shows 90 psi across all cylinders. This looks to be a few psi under the 6.5 bar minimum service spec in the factory manual - tired but it did run. On to the other side...

Pass head from front to rear shows 60, 20, 35, 70 psi

Yikes.

I own a leakdown tester kit and a coolant pressure tester. Here is my plan of action before I take the head off

1. Take old radiator off car and pressure test the oil cooler and ATF coolers to see if either leak into the coolant, and pressure test the coolant passages and see if that leaks back into either cooler. If the radiator checks out fine, which I fear it may,

2. Leakdown test the cylinders 1-4 with low compression and see if I get noticeable pressure out the intake, exhaust, or coolant passages.

3. If neither of the above turn up anything time to take the intake and heads off and look for obvious blown head gasket, and have valves pressure tested if not.


Can anyone comment as to whether given the milky coolant but not milky oil, and very low compression on the entire passenger side head, whether this is likely a head gasket/warped head? I figured a blown head gasket across that many cylinders would have turned the oil into a milkshake but it hasn't.

The other thing I'm thinking is because the water pump was completely blown on this car when I got it (you could rock the pump shaft 1/4" side to side in its bearing, I have never seen anything so bad that still ran) that this car was badly overheated by the previous owner and warped the head(s).

Just thinking aloud, I welcome any comments from you guys. I intend to fix this car one way or another since it is intact and generally in decent shape, plus I just dropped some money on this car and hope to at least be able to drive it. I have dropped $3k in parts this month to rehab it from its sad state. I have a fascination with reviving cars people gave up on, sometimes it works out great and sometimes it doesn't.

If anyone wants to see pics of the car and my progress on it I keep albums here of pretty much everything I do (and on any other cars too).

http://bondospecial.smugmug.com/1986Porsche928S

Here it is in its current state:







I thought I had gotten somewhere w/ the timing belt, w/p, tensioner (and brakes, wheels, and tires) completed but tonight's compression test results really put a halt to my sense of progress!!

Thanks!!

Steve

Speedtoys

The low compression could be stuck rings...I dont recall how to 'free' them up..but..its worked before.

Bondospecial

I will add "squirt oil into plug holes of cylinders 1-4 and re check cranking compression" to my list of things to do. I find it weird though that one whole bank is so much worse and less consistent than the other.

IcemanG17

Since the car sat for such a long time, its safe to say it effectively turned into a "battery" in the radiator-engine and that toasted the head gasket....I am SURE there is significant corrison on the main studs as well.....I saw one that sat for 10+ years and one of the studs literally rusted through, broke and caused a head gasket leak.... How much rust was on the original waterpump....that probably looked horrible

A leakdown test will quickly tell you where its leaking.....stuck rings due to gunk is possible.....thats your ideal scenario...but given the milkshake oil......its time to pull the engine for headgasket work

Bondospecial

The oil wasn't a milkshake, only the coolant was. The water pump wasn't corroded at all, just had a very broken bearing(s). This engine had almost no coolant in it when I got it, so it was likely sitting nearly dry for 12 years. Sounds like best case scenario is that I will get away with having to replace head gaskets and have the heads leak checked and flatness checked. Time to read up on engine removal...

Cosmo Kramer

Like others said could be stuck rings and/or sticky valves. Some run time may improve the numbers. Does the cooling system hold pressure?

Just an FYI, judging by the pictures I would say your PS cam gear is done., pretty shiny looking where the belt rides meaning the hardened coating is gone.

Bondospecial

I am going to put the new radiator on and check the cooling system, and I will do a wet compression test to check rings. Will report back shortly, thanks

Mrmerlin

its a safe bet that you have to pull the engine out and do a valve job and new headgaskets.
Further testing will eventually lead you there.
With a refreshed top end the engine should run well that is of course if the rings are not rusty from a leaking headgasket

86'928S MeteorGrey

Unless you get a break with your next compression check, you will be on the engine removal train. The 32V engines before the S4 have studs that prevent the heads from being removed in-car. Some have tried to pull the studs... TRIED. Don't try it. Put the motor on a stand and do it right.

Bondospecial

Thanks for the tips. Will I be able to reuse the studs if I don't try to pull them? Or are they a one time use item?

Mrmerlin

studs can be reused if they are not damaged from corrosion
The studs are glued into the block with green locktite so they are very difficult to remove,
you need to heat the block to loosen the sealant

Landseer

My 85 was out of commission for over 10 years.
It had oily water.
Not sure the source, but it seemed to be partly from coolant hoses breaking down inside.
Flushing, running and coolant changes cleared it up. Just turned 20,000 miles since the refurb, runs great.

Your issue is bigger, likely dictating the pull.

Bondospecial

Surprising results. I just squirted oil into the cylinders with the lowest compression (20, 35, 60 psi) and cranked them, and I got 150+ psi in all 3. I have the old rad out in the garage right now, I am going to pressure test the coolers to see if the oil in the coolant was atf or oil from a cooler (dual cooler car). Maybe I have a ring sticking issue alone, or possibly a ring sticking issue combined with a very small head gasket leak on that bank. Not sure but I'm investigating, once I see what the rad coolers look like pressure test wise I will put the new rad on the car and do a leak down test on the engine and assembled cooling system.

mickster

You're going to fit in nicely here. I love that color!

Bondospecial

Hey thanks mickster! Ok radiator cooler test results are in, both ATF and oil coolers hold perfectly @ 60 psi test. So the milkshake coolant and sticking rings on bank 1-4 combined tell me I might have a small head gasket issue on bank 1-4 leading to the addition of stuck rings from sitting. I will put a rad back on the car and do a cooling system pressure test and leakdown just to see if I find anything else that seems to make sense with this theory.