Damn! Blown oil cooler!

ahdoman · 04-12-2009, 02:17 PM

Is this what happens when a thermostat sticks in the open (hot) position on a cold start? Any other ideas what would cause the oil cooler to blow apart at the seams in the center of the cooler?

turbobrat930 · 04-12-2009, 02:23 PM

I have a perfect condition used one...if you are interested.. I would have it sonic cleaned before use.. but perfect condition.. cam e off of my 3.3L turbo...

ahdoman · 04-12-2009, 03:39 PM

Thanks for the offer Turbobrat but I've got another one at the ready. I just want to know why this would happen so I doesn't happen to the other one!

turbobrat930 · 04-12-2009, 04:22 PM

I would think that the thermostat was open when the oil was cold.. causing the excessive pressure with the thick oil...

Eagledriver · 04-12-2009, 08:52 PM

The oil cooler gets full pressure even if the thermostat is closed. That damage looks severe. Are you sure the cooler didn't get hit or bent by some external event? If the damage is due to pressure then you have a pressure relief problem.

-Andy

ahdoman · 04-13-2009, 05:13 AM

How does it get full pressure if there is a Thermostat in front of it? Does the cooler see the full pressure with less flow when the oil is cold? This occured at startup with the engine stone cold.

J P Stein · 05:59 AM

My pressure gauge will peg at cold start(8 bar +). This lasts for 3-5 sec then drops quickly to a reasonable number...6 bar or so at 2k rpms.
I doubt the thermostat is a perfect seal but is should protect the cooler(s) from this initial jolt....assuming it is a slow leak. Pure speculation here.

T77911S · 04-13-2009, 05:57 AM

mine will hit 100+ in the winter. i keep the rpm's low so it will not go over 100. i hear that will blow an oil cooler. i would think the T stat would protect it, but i a not taking a chance.

Flieger · Flieger's Garage

The pressure relief pistons in the case are what relieves the pressure. The auxilary thermostat (and the engine thermostat, too) are not open at start-up. They will keep the pressure from getting to the front cooler.

Eagledriver · 04-13-2009, 03:15 PM

The outlet of the cooler is connected to the main oil galley that goes to the bearings and squirters. That galley sees full oil pressure therefor the oil cooler sees full pressure. The cooler isn't feeding that galley like it does when it's hot but that doesn't make a difference.

Basically both sides of the cooler see full pressure when the engine is cold (therefor no flow). When the engine is hot the input side of the cooler sees full pressure and the output side sees slightly less pressure (therefor the oil flows through the cooler).

-Andy

lucittm · lucittm's Garage

ahdoman,
What brand and weight of oil are you using? It might be a bit heavy for your application.

I would think that if your oil pressure caused the cooler to deform like that, there must have been a structural integrity issue. When I have oil components (tanks, valves, coolers) hydrostatically pressure tested, I specify 2X working pressure which is, rounded up, 250 psi. That would be exactly 232psi (2 X 8 bar) for the cooler in my car since the safety valve is supposed to open at 8 bar. The tank vent is rated at 180 psi but that is not your problem.

Eagledriver is right. I would recommend that you pull your relief valve and your safety valve and check for clogging.

If your oil gauge is pegging then you have no idea what the real oil pressure is in your engine. Even cold, the thicker oil should not peg the gauge if you are running the proper viscosity oil and the dump valves are working correctly. I have heard of people shimming those valves. Don't do it. They are there for a reason and they are engineered to be ultra reliable.

Good Luck,
Mark

ahdoman · 04-13-2009, 05:45 PM

Hey guys, this is great info thanks!

Andy - I need to pay closer attention to my oil flow chart. I see now how the thermostat doesn't keep the oil out of the cooler but it's more of a flow direction regulator.

Mark - I'm in SoCal and was using 20/40. I'm also trying to make sure the pressure relief and safety pistons are working. Anybody have a good way to remove them from their bores from the outside of the case (obviously the plugs and springs come out)? I tried a magnet but it isn't strong enough to pull them out. Also, if their stainless that won't work.

E Sully · E Sully's Garage

The oil cooler only see's the low pressure scavenge pump. When the thermostat is closed the cooler see's no pressure.

TimT · 04-13-2009, 06:04 PM

Quote:

The oil cooler only see's the low pressure scavenge pump.

In the schematic you posted, the engine mounted cooler is on the pressure side..

The fender mounted cooler is on the scavenge side..

lucittm · lucittm's Garage

ahdoman,
I think 20/40 is too thick for your car in Cali. I ran 10/40 in the summer in my 911S when I lived in San Dog. Consider that many are running synthetic 0W-40 now. But whatever the owner's manual says is good, go with that. In any case, I might try 10/30 and see if I can keep the gauge from pegging even at startup.

To remove the dump valves, remove the captive nuts and the pressure springs. Start the car for a few seconds and the relief pistons should pop out. Oh, and put a big pan under the engine first.

Later,
Mark

ahdoman · 04-13-2009, 07:29 PM

Mark - I've tried that and they won't pop. Although the problem may be the fact that there's a big hole in my oil cooler and all the pressure relieves itself there instead of at the valves! Also, since I have such a large oil leak I don't want to run the car too long and risk other interior damage. I do however have another idea;

If anyone has a couple of the pistons could they please measure the inside diameter? A picture of the backside (the side the spring sits in) would be nice also. I may need to make a rubber compression tool to pull them out. Also if anyone has a case split it would be good to see the orientation of these passages in a case (2.7 CIS 7R case).

Flieger · Flieger's Garage

Here is a case half:

lucittm · lucittm's Garage

ahdoman,
If those valves don't come out under even partial oil pressure, you have found your problem. I cannot help you with the size right now but it appears that you will be replacing them anyway. You can take a large wood screw and use it as a puller. Hopefully, your cases are not damaged.

Mark

eclipse66 · 04-15-2009, 09:58 AM

Hello ahdoman. Check out this story as well:

Need help. Too much oil pressure blowing up coolers

Best, Dave

ahdoman · 01:38 PM

Thanks again for the input everybody. I pulled the engine and took the thermostat out and it failed the boiling water test; the passages didn't change. I'm going to take it apart and see if something is obvious.

In regards to the relief pistons; check out this "piston pulling" tool I made. It's a 5/16" concrete lag with a piece of shrink tubing over it. It worked great! Put it in the bottom side of the piston, turned the bolt a couple of turns, it opens against the piston and then pull it out! The pistons weren't severly stuck it's just I had no pressure in the oiling system with the blown cooler to push them out.

Dave - Thanks for the other thread. I've checked it out but it brought up another point; one of the posters mentions that there are two different spring lengths for the releif pistons (long 86mm spring vertical, short 70mm spring horizontal). However, according to the PET for the 2.7 it only shows one part number for both springs and pistons. Both of my springs are the same length. Are they supposed to be 2 different lengths?