mark kibort

not a lot, but a little , and it could have been due to the engine over heating for a second, or being stored with no water for so long? (oil seepage) I guess I could drain it , refill and make sure, but how does this happen?

compression good 200psi each hole. no water in the oil, but a black (or red due to amsoil) haze at the top of the resevior. car runs strong, no steam out the exhaust, things look good, except........

what are the possibilities.
mk

marton

Do you have the standard 928 radiator with the oil cooler in the plastic side tank? If so the oil cooler could be leaking.

Landseer

Possibly, as in my case with a 10 year sitter, sludge/ degradation of old hoses.

James Bailey

What radiator ? new old ??

mark kibort

Old original radiator
worth fixing?

Ducman82

id take it to a rad shop and have the side tank pressure checked...

IcemanG17

since the compression is so good......my thoughts are a slightly leaking end tank....but headgaskets don't like to sit either?

tveltman

You can do a leakdown test with the cap off of the water tank, and if you see bubbles in the expansion tank when the cylinders are pressurized, you've got a blown gasket or a cracked head/block. If it's just a little oil, and the car isn't burning oil or water, then I think it's unlikely. Of course, I suppose that a negative test result doesn't mean the problem isn't there. "The absence of evidence is not evidence of absence", as it were. Good luck!

mark kibort

Thanks. I totallly forgot that the side tanks can leak into the radiator. BUT, why would that be a one way valve? if there was an oil leak, (I suppose the tank is under full oil pressure, right?), why wouldnt water enter the oil tank when the engine was shut off? could it be that the water is only about 1 bar, whereas the oil is more like 5 bar, and maybe that leak wouldnt really be a leak at 1 bar?

Ill do the leak down test to see if there is any bubbles by pressurizing the cylinders with air.

Help me understand how else the oil can get into the water jacket. if its head gasket, wouldnt it be more likely to have water in the oil? where are those high pressure oil lines going to the heads?

tveltman

Well there are water passages in the block, and the oil must get into the heads somehow, so there must be oil passages. There will be a gasket between the heads and the block (obviously), and if the gasket fails at that point, then you will get crossover. I suppose that if there is no water in the oil, then you wouldn't expect to see oil in the water, but who knows...

GregBBRD

Mark:

Fluid exchanging problems are usually hard to figure out, when they first start. Try the oil cooler in the radiator first and hope that is what is wrong. It gets ugly quickly, if that is not what is wrong.

If the oil cooler is bad in the radiator, I can send you a radiator that you can steal the cooler from.

mark kibort

Thanks greg! I hope I didnt cause the engine any damage, by the slight overheating. The temp started to climb but I was moving and It was always very cool out. turns out those little vents in the nose had shut. it seemed the light went on before the gauge went to the second white line, so as soon as it went on, i shut it down. It also was doing a lot of backfiring when I would floor it, due to the cracked distributor cap. thought that might have damaged soemthing. I didnt think of the oil cooler as a sourse, but that makes the most sense. first because there is no water in the oil, no steam and all the plugs are all carboned out due to the rich mixture, and not water cleaned.

Ill try the leak down test and see what that tells, and if that shows negative, Ill take you up on the radiator oil cooler salvage offer. Thanks again!

how does the oil cooler attach to the radiator? and if there is a leak where oil is pushed into the radiator, why is it that the water isnt pushed into the oil cooler and then the oil supply? I hope this is what it is, I dont need any more issues!!

Mark

IcemanG17

MK
If there are some small cracks in the plastic end tank then it should leak oil into the water...since the oil is at a much higher pressure vs the water.... its pretty easy to pull the radiator and get it checked..... I think the typical end tank failure is where it leaks water out of the radiator...

Another idea is that some oil got in the water while it was out...maybe just a bit dripped in an open hose line or something....could be nothing.....it doesn't take much oil to make a sheen on water

GregBBRD

Here's how it happens:

Oil at 5 bar, goes through a little tiny crack in the cooler. Water less than 1 bar...which will only be greater than the oil pressure with the engine shut off. The crack has to be small enough that it only lets fluids through it at pressures greater than 1 bar.

Sounds silly, but that is what happens with little cracks. They usually get bigger.

Make sure the radiator shop tests the cooler at 120+ psi, not 14 psi.

mark kibort

Thats kind of what I was thinking, and I hope that is the case. sure sounds like it, because that radiator took quite a hit, and I thought it was a miracle that it survived, so maybe it didnt.

I guess Ill pull it and the shop will know what to do, and Ill mention the 120psi test.

I was checking out some block pics and noticed the single hole that the oil is pumped up to the heads through. I guess it enters the head through the front on the driver side and the rear on the passenger side under pressure. If it doesnt leak into the water jacket at that point through the head gasket, I dont see how it can push through anywhere else, unless the heads are cracked. all the other oil paths are big and open as the oil just falls to the pan with gravity from the heads after it finished its job with the cams.

So, in overthinking about it, it sure sounds like the radiator cooler.

Again, thanks for the offer of the radiaotr with good oil tank. Is it a straigth forward job for a radiator shop, or should I find one with porsche 928 experience?

Mark