Oil cooler height a problem?

[4vpc]

I built an engine for a guy and he fitted it, it's a basic 4 pot, turbo, crank mounted oil pump, nothing special. The previous ones had suffered multiple failures, poor engine building and bad mapping had seen blown head gaskets, melted heads, run crank bearings etc so he came to me and and my mapper who I know is good.
When he'd done and had it mapped he brought it over for a look and it's running low oil pressure. It's about 10psi at hot tickover, 30 - 40 psi cold tickover, but picks up ok with some revs to about 90 at 6k hot, which doesn't mean death, but it's not great and it's lazy on the capillary gauge. Given it's just spent some hours on the dyno and the oil filter was clean as a whistle I know we haven't got bearing damage. He said it had low oil pressure right from the first start.

Anyhow there is the background, the only thing I can offer up as an anomaly is that a different oil cooler has been fitted much higher up (about a foot) than the original was, I'm pretty sure it's draining its contents into the sump when the engine is off and is also probably accountable for the slow rise in OP when the car is started, but here is the main question; can it be held responsible for continual low OP? Can you get an airlock in an oil cooler if it's mounted higher than the pump and filter?
It's getting to the point where i'm going to strip the front of the car, undo the cooler, let it hang down and see if it makes a difference.

[Kevin Johnson]

http://www.speedzilla.com/forums/ducati ... #post43166

[4vpc]

http://www.speedzilla.com/forums/ducati ... #post43166

I'm looking for some facts really, not just a random conversation I found via Google.

[Kevin Johnson]

The link is a gentle suggestion that you need to provide more facts about the particular system and exactly how it is plumbed.

[pamotorman]

if the oil cooler inlet and outlet are at the top it will not drain when the engine is shut down. every 90 degree fitting in the plumbing will reduce the oil pressure 5+ pounds. also the fittings can cause a restriction if their inside diameter is too much smaller than the inside diameter of the hose

[modok]

Most oil filters have anti-drainback valves.....and they do work. Strange oil cooler setups do NOT usually cause low pressure.

Low pressure at idle only is often caused by:
-loose oil pump clearances
-poor sealing of oil pressure control valve(s)
-loose clearances of overlooked less critical items such as cam bearings, lifter bores, balance shafts, or just plain leaks in some odd part.


An air leak on the suction side of the pump, or any air bubbles in the system, causes strange fluctuations in pressure, it will wander around from almost zero to 20, but not just plain steady low pressure.

[cjperformance]

You say a different oil cooler has been fitted? Can you retest it with the old cooler and associated lines/fittings jigged up?
Id be looking 1st at different cooler flow restriction and as mentioned the fittings if they have also changed.
The height of 1' all else being ok is not a problem, well not in anything i have done which is mainly 6cyl and V8 stuff.

[Kevin Johnson]

Not a good idea to use the actual old cooler from a previously failed engine as it will often have debris lodged in it that releases upon reuse. A duplicate but new one could be used in the experiment.

[Momus]

Run it with the cooler bypassed first.

[4vpc]

Thanks for the responses, a few things for me to think about there. I'll do the simplest most obvious suggestion first and hook up an original style cooler and see what happens, it shouldn't take long to do this.
I'll have a good study of a stripped engine and an oil flow diagram to see which way everything is going to for certain.
Regarding ADBVs in filters, it does have one as the filter is mounted upright (threads at the bottom) and it does work well, but as far as I know this is to hold oil in the filter and nothing more.

You know when you do such a good job of an engine and it comes back in looking like new with no oil leaks whatsoever? That's where i'm at, so initially i'm trying to avoid taking any pumps or sumps off as I know it'll never seal as well again once i'm trying to do it from underneath whilst still installed

[4vpc]

Run it with the cooler bypassed first.

That's not a bad idea either, but i'd have to have a link hose made up or blank off the outlet & inlet. Putting an original style cooler is easier as I have one anyhow.

[bentvalves]

as long as it remains at 10psi hot idle, and doesn't slowly start losing pressure over time, I wouldn't worry about it that much.