6.5 Optimizer Oil leak, possible low pressure

[kontour]

Hello, new to the forum but there seems to be a lot of great info here.


I own a 1985 HJ75 that has been fitted with a 6.5 Optimizer running a turbo and intercooler. Purchased it already converted from the previous owner who estimated it had done around 70000kms.


Couple of questions, my oil pressure sits somewhere around 10-15psi at a hot idle and when cruising at approx. 2000rpm it sits around 30-35psi. Is this ok or does it indicate an issue?


The second question may be related as I have noticed a small oil leak from the intercooler plenum and when I pulled it off today it appears oil has been leaking from the plenum gaskets, however the inside of the intercooler and the rocker covers looks pretty clean.


https://imgur.com/GVUEftQ.jpg


Anyone have an idea what may be causing the oil leak? The bolts on the plenum were not torqued particularly tightly at all but I'm aware there really should be any oil on that side of the intake. There is an oil catch can fitted to the engine already.


Any ideas would be greatly appreciated as I've reached the limit of my knowledge on this. Thanks!

[DmaxMaverick]

Welcome aboard!

Your oil pressure is fine, and quite typical. I don't believe it to be related to a leak. Any leak that is associated with oil pressure drop would be a LOT of oil leakage, and you'd notice a lot more than a bit of seepage, anywhere.

I'm not understanding where from it's leaking. If the intake plumbing is clean inside, as it appears, the leak must be coming from somewhere else and is just accumulating there. The plenums aren't a source of fluid leakage, otherwise. The corrosion in the bolt holes look like they need some attention, though. The rubber gaskets require minimal torque to seal properly, but do require balanced torque to remain healthy over time.

By "oil catch can", do you mean the crankcase vents to atmosphere, rather than to the intake? That leaves the only place oil can be introduced into the intake would be from the turbo. If no oil residue is in the plumbing, then there should be no oil to leak out of it.

[kontour]

Welcome aboard!
By "oil catch can", do you mean the crankcase vents to atmosphere, rather than to the intake? That leaves the only place oil can be introduced into the intake would be from the turbo. If no oil residue is in the plumbing, then there should be no oil to leak out of it.

Thanks for the reply!


The crankcase still vents to the intake, but in between the PCV and the intake is a metal can that is designed to separate any oil out of the gas coming out of the crankcase, sending air back to the intake and hanging on to any oil.

Its probably been 1000kms since I last serviced the engine, so this has happened since then. I'm using a full synthetic 15w50 oil.

I'm having trouble working out where this oil is coming from, the main areas appear to be around the plenum gaskets, there was a little on the top of the plenum itself as well as a thin coating on the rear of both rocker covers with some build up in the v between them and the head. Also on closer inspection I've noticed a little bit in the V under the fuel pump, as well as a coating on the underside of the oil pan and the bell housing.

There is no other oil on the bottom of the intercooler, bonnet etc and the front of the block is clean too

The photo was taken after I'd hit the areas around the plenum with degreaser as I didn't want anything ending up in the intakes when I pulled it off.

If it was the turbo of a main seal or something I'd be expecting to see more oil around the turbo etc.


This has me stumped!

[DmaxMaverick]

What you describe sounds like a valve/rocker cover leak(s). It is the most common, and nothing else comes to mind at the moment. I suggest cleaning it up and watch it closely, often. The rear of the engine valley has a drain, so any accumulation of fluids there will drain down the back of the block and onto the rear pan and bell housing area. The valve covers are simply sealed with RTV (NO gaskets!). Many old and recent posts here on the procedure, but we can go over it again, if you need.

[DmaxMaverick]

Also....

Your "catch can" appears to be very effective. Much more than most, in my experience. Make sure it is not blocked and is venting freely. If not, it can allow higher crankcase pressure, leading to leaks (valve covers are most vulnerable). A properly operating CDR valve (PCV - the tuna can on the R/H valve cover) will maintain slight crankcase vacuum, which prevents most external leakage opportunities. If it's failed, it could explain the sudden leakage. I don't think any of this is related to the intake plenum.

[Robyn]

On most 6.5 turbo installs the CDR "TUNA CAN" vents to the air inlet close to the turbo inlet housing.

This creates the small vacuum needed to scavenge the crank case gases.

You mentioned that yours was vented to the intake ????

Can you post some pictures of the setup please ???