Big Oil leak!

[DDS]

Hi guys:

I have a leak that appears to come from my oil cooler. The engine is newly rebuilt with a blueprinted pump for FAT and the high pressure relief pistons. The gauge pegs at 70psi when cold, and drops to 10psi or so at idle when hot, up to about 60 when revving.

Should it be that high when cold?

The leak runs at the rate of an annoying faucet drip, and can leave quite a puddle if the car is left idling. The oil seems to be coming from inside the cooler or possibly at the seals. I though I had assembled it carefully, though I was told I was missing some thick aluminum washers. I tried pressure testing the cooler with compressed air and a pail of water, but could detect no leaks, though it was more like at 10psi than at 70.

Is there an easy way to pressure thest the cooler? Is that the likely culprit?

Any other suggestions?

Many TIA, Dave

[Jake Raby]

did you install washers between the cooler and thecase?? was the cooler leaking before? what is the history of the cooler? what seals were used?

[Dave at Pelican Parts]

Whomever told you that you were "missing" washers was thinking about Type I/II/III engines, not Type IV or 914 engines. There aren't any on the 914 cooler, at least not between the cooler and the engine! (Tom Wilson's book is a little misleading here, as he talks about all the Types of engines at once.)

It is common to see cold oil pressures going very high, because oil is much thicker when cold than when hot. 70-90 PSI is not uncommon. The pressure drops when the oil warms up. You want to see at least 10 PSI per 1000 RPM, up to the point where the pressure relief opens up. (~50-80 PSI or thereabouts.) Less than that is a problem, more than that by a reasonable amount is not.

Prime suspects are the oil cooler seals (they can get in there crooked every once in a while if you work at it, LOL!) the oil pressure sender just aft of the distributor, the distributor shaft O-ring. The coolers themselves do leak, but pretty rarely. It does seem to be becoming more common, though.

--DD

[DDS]

Thanks gentlemen. The washers were not between the cooler and case, but between the cooler and nuts, there is nothing between the cooler and case but the seals which I had installed pretty carefully (I thought) torquing to the requisite insanely low torque. Seals came with a german mf'd gasket set I bought - I forget whose. Are some troublesome? They appear to be sitting 'true' in the case still. I did forget the bolt that secures the bracket on the other end of the cooler... Could it have been vibrating around?
The cooler was with the engine which had sat for years, so you never know.
I was unable to detect a leak at the sender base or the dizz (a new Mallory), so I'll proceed under the assumption that is the seals (appears unlikely) or the cooler. Thanks!

Dave

[Dave at Pelican Parts]

OK, you do want washers between the cooler and the retaining nuts. You also do want the outer end of the cooler supported. I don't think lacking those would instantly cause a large leak, though.

Not sure off the top of my head where else the oil could be coming from.

--DD

[DDS]

thanks Dave. It is a bit odd. The leak wasn't all that instant, It seemed suddenly to get worse. Now, I was running the car in early April, in temps just above freezing, something I didn't do last fall, so that may have caused the oil cooler to fail.
I spoke to a rad shop today about pressure testing and they were pretty gun shy about oil coolers (they seldom test them in water cooled cars - pressure differential always causes oil in coolant). the guy told me that oil coolers that test fine often do leak under heat, pressure and vibration, so testing isn't necessarily conclusive anyway. I think I'll just replace it, and verify the dizz and oil pressure sender and case bolt and oil pump torques anyway.
This gets me thinking about supplemental oil cooling.... I'll start another thread.
Thanks again.

Dave

[silver2.0]

I had my cooler go bad very recently, and I can tell you what happened. I thought I had put mine together carefully too, but the bracket that secures the end of the cooler was bent slightly. When I tightened it, it sqeezed the cooler just enough to make it leak. It was a 30 year old cooler, so it probalby wasn't in the best of shape before, and I just sent it over the edge. I bought a new cooler, and fixed my clamp, and now no oil leaks!

[DDS]

Just to close the loop - the (well, that )leak is gone. It was the oil cooler, and it had failed. I bought a new one (nice, German) from California Import parts. Thanks for all the input.

Dave

[John Rogers]

When I had my big 4, it had tremendously high oil pressure when cold and I had a bright orange line on the VDO temp gauge to remind me to "NOT REV OVER 3500 RPM UNTIL TEMP GETS TO HERE", 140 degrees. Good luck