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View Full Version : RB25DET Oil leak from exhaust manifold?


Ptrain
11-08-2020, 05:56 PM
I've been having an issue with my 95 skyline gts25t being very hard to start and when it does start it has a really rough idle. It came out of nowhere. Today when I started the car up it was billowing smoke out of the exhaust and leaking a lot of oil.

The oil looks like it's coming from in between the head and the exhaust manifold right at cylinder 6? I'm pretty sure the oil isn't leaking from the valve cover. And I can clearly see bubbling coming from where the exhaust manifold gasket would be.

Also, am I missing an exhaust manifold gasket stud? The car is 100% stock so it would be weird for someone to have messed with the mani.

Here's a video with the engine running. Any thoughts?
https://imgur.com/a/2BiYWYU

S14rebuild
11-08-2020, 07:58 PM
dont continue to run/drive the car

Is that oil i see where the coil packs go?

Check compression and plug condition....

Ptrain
11-08-2020, 08:17 PM
Na I think that's the wire loom for the coil packs that is shining in the light.

Yeah i'm going to do both tomorrow and report back. I'm very interested to see if the spark plug is covered in oil.

jedi03
11-09-2020, 11:56 AM
you thinking bad valve cover gasket? could cause it, hope the plug is clean and its not ring issue...

Ptrain
11-09-2020, 08:55 PM
Cyl 6 and 5 spark plugs had oil on them, the rest were ok. Cyl 6 compression was 150, the rest were 130-135psi.

I'm going to do a leak down test tomorrow.

SpaceKADET
11-10-2020, 05:58 PM
Looking at that video, I don't think it's your valve cover leaking as it looks pretty dry in that corner. You are definitely missing a stud there though.

Based on what you've said so far, I'm almost suspecting a blown turbo oil seal. Now I don't like suggesting big things like that right off the bat, but that's the only thing I think would cause an issue with the rough idle. Is the car regularly driven?

Is it possible that at some point, someone put a stud or bolt in where you are missing one and it was too long and punctured into the head because they just sent it in there?

Higher compression on that one cylinder suggests that some sort of fluid is getting into the combustion chamber, but I'm curious as to how. Is the turbo manifold a top mount or bottom mount? If it's a top mount, that would again point to possible issues with the turbo.

Ptrain
11-10-2020, 10:31 PM
The turbo is the stock bottom mount. So the oil must be coming from the head gasket or the valve stem seal.

It doesn’t get driven that much but I’ve driven it probably 1000mi since I’ve bought it without issue. It’s only been recently that i first got a rough idle and it felt down on power. And about 40mi later after parking it for a week it smoked like crazy and is showing this leak.

None of the auto parts stores had a leakdown tester so I ordered one off Amazon and will see what it says tomorrow.

SpaceKADET
11-12-2020, 09:51 AM
Is it possible the fluid isn't oil and the fuel injector for 6 is either stuck open or some other injector fault is present?

Ptrain
11-12-2020, 10:19 AM
The leakdown test was inconclusive. Maybe the cheap leakdown setup I got off amazon is crap. The best leak percentage I could get on any cylinder was 60%. But none of the readings were repeatable. Another thought I had is every place I read said you should warm the engine up before doing the leakdown test. And I haven't tried starting the engine at all since I discovered the oil leak.

Yeah unfortunately it's definitely oil on the spark plug.

When this all started it was just a rough idle and I was down on power. I tried unplugging each coil pack one at a time with the car running to see if that would make the idle worse. Unplugging 1 and 2 made the idle worse. Unplugging 3 made no difference. I swapped it's coil pack with the pack from 2 and the issue remained with cylinder 3. I figured maybe the injector for 3 was clogged. I replaced all the injectors with OEM sized injectors. Tried starting the car up and it ran fine so I thought that was the fix. But a week later when I went to start it up again it wouldn't start and that's when I got all the smoke and the leak.

SpaceKADET
11-12-2020, 10:37 AM
I had that exact issue on an RB a few weeks ago and it ended up being that the trigger signal wasn't being sent to cylinder 1 from the ecu. Ended up being a bad ECU. It went from running like a top to missing bad on ine cylinder. Not saying that's your issue, but if you have a dead cylinder and swapping coils and plugs from another cylinder doest pick the cylinder back up, it's something to consider.

Ptrain
11-12-2020, 11:06 AM
Interesting, how did you end up diagnosing that issue?

S14rebuild
11-12-2020, 11:11 AM
I had that exact issue on an RB a few weeks ago and it ended up being that the trigger signal wasn't being sent to cylinder 1 from the ecu. Ended up being a bad ECU. It went from running like a top to missing bad on ine cylinder. Not saying that's your issue, but if you have a dead cylinder and swapping coils and plugs from another cylinder doest pick the cylinder back up, it's something to consider.

This wouldnt cause oil to build up in the cylinder or massive smoke pourn out the exhaust

SpaceKADET
11-12-2020, 12:10 PM
Interesting, how did you end up diagnosing that issue?
I had good power and ground at the coil pack, moved the coil and plug to a different cylinder and the issue stayed with the cylinder. Compression was good across the board. I ohmed out the trigger wire from the coil pack all the way to the ECU and checked to make sure it wasn't shorted to ground, the wire was perfect. To confirm the diagnosis, we had to get another ECU with a basemap on it, plugged it in and picked the cylinder back up.

Yes S14rebuild, having the ECM drop signal to a cylinder wouldn't cause the issue with the oil, but it's possible the car has multiple issues.

Ptrain
12-12-2020, 04:36 PM
Well update on the skyline. Early on in diagnosing this rough idle i thought it might be a clogged injector. I pulled the rail and most of the injectors were missing parts of the plastic pintle cap. So I bought some 370cc stock flow deatschwerks injectors and installed them. Soon after I started get the smoking issue.

I didn't realize that deatschwerks didn't have the greatest reputation and thought maybe one of them was stuck open or one of their o-rings failed and was flooding the cylinder. So I figured i'd pull those out and go with legit oem injectors. I just installed them and no change to the smoking.

But fluid (oil or gas, now i'm not sure?) is no longer coming out in between the head and the exhaust manifold. Instead i've got a coolant leak coming from somewhere near the back of the block. It's a pretty good leak at this point.

So symptoms are a lot of white smoke (like a lot a lot) out of the tail pipe, some light smoke around the exhaust mani and turbo area, a coolant leak near the back of the engine. Also the stock boost gauge on the dash was showing 0 psi at idle. I just noticed that today, before it would show some vacuum at idle. I may have just not reconnected the vacuum line to the boost sensor. I've got to figure out where that is.