I recently used a bore scope to see if I had a leaking coolant at the crossover pipe. I saw liquid and assumed it was coolant. Thinking that I had to do the crossover pipe, I pulled the intake manifold. Turned out to be oil!
Two things surprised me. One, the engine was rebuilt 20k miles ago. Look at the pics of the intake manifold valves....they look like they've been in there for 100k miles! Second. I found oil all around the rectangle cooler in the little nooks and crannies. The oil was evenly distributed all around the rectangle cooler. I did not see any leaks running down from the valve covers. I know that the intakes can have oil in them but that is generally seen when you pull the intake and tip it a certain way causing oil to drip out. I can only guess that the source of the oil is the gasket that runs around the oil cooler.
So a few questions about replacing the gasket.

1) Can I just remove the cooler bolts and pull it up while carefully sliding out the oil cooler pipe? If I go that route, will a ton of coolant shoot back towards the now open top of the block? I can drain the coolant from the lower radiator hose if that's advisable.
2) Idle was a lilt bit rough after I replaced the intake manifold. I carefully torqued the 8 bolts and checked all vacuum lines. Can a leak at the oil cooler gasket cause a vacuum leak?

oil located around cooler on LR4 5.0


lr4 5.0 valves with 20k miles

 

Any advice on replacing the gasket on the oil cooler? Assuming I should drain coolant first. Once bolts are off, just like it back since the oil cooler tube is in the water pump?

 

I rebuilt the top end of my engine a few months ago. But looks like my oil cooler or just it's gasket is leaking. Where I've replaced it before, I'm not too worried. But how'd it go for you? Fix the problem?

 

I haven’t done this job, but a little oil sitting on top of the engine doesn’t necessarily indicate a leak in the oil cooler or gasket. The PCV system is not great on these cars, and a lot of oil seems to get past and into the air intake - pretty well documented in the forums. I wouldn’t assume there’s a gasket leak just because you see oil there with the intake off.

 

Thanks for the info. I'll take a closer look at the air intake plenum and related gaskets. I have noticed oil in the plenum before as I was redoing head-gaskets. And I noticed that one of the air hoses on the back of the plenum is a simple rubber sleeve that could fall off and maybe be a source of oil from PCV system to drip into valley.
So, it's all worth looking into.

The oil seems to eventually leak over the front lip of the valley and down the front cover area. In fact, I started my investigation assuming I had a leak in the front cover or the front crank seal. But it seems pretty clear that the source of the oil on the front cover (and, eventually, the ground) is from the valley. How it gets outside of where it should be to accumulate around the oil cooler is the small mystery.

 

Interesting. Let us know what you find. Pretty common oil leaks towards the front of the engine are the valve covers, timing chain covers, and vacuum pump (internal seal leak). The vacuum pump is something to check. On the V8, it seems to be connected via vacuum hoses to the intake, and when it fails, oil leaking inside the vacuum pump can actually get sucked into the air intake in large enough quantities to cause smoke on acceleration. I haven’t heard of oil cooler gasket leaks being a problem on this car, but that’s obviously a possibility as well.