So I knew I always had a bit of an oil leak at the rear of the intake manifold.
I took my car for its MOT this time last year, when the guy did the fast idle emissions test (@2500-3000rpm) the intake started to leak bad and put a patch of oil on the floor about the size of a large footprint in around 2 minutes.

I got around to taking the intake off about 6 months ago and put new gaskets in and RTV'd it all up.
I thought I'd cured it until recently when I've been smelling a bit of burning oil when parking, its wasn't dripping on my driveway so I didn't worry about it.

I've just had my latest MOT today and during the fast idle test it literally started raining oil underneath It must have laid down a patch three feet across in 2 minutes??

Should it be that bad? What would make it blow oil that badly? Are my rings shot?

The other problem that may be related is the fact that the tester had a hell of a job to get me through the lambda test, it took two extra guys to stuff up the tailpipes with rags to bring the lambda down to acceptable levels.
Is this related at all do you think, maybe another sign that the rings my be worn?

PCV system appears to be intact and the valve is doing what it should.
Engine has covered 58,000 miles.

Cheers!
Scott

 

I have never heard of such a bad leak before. I know you need a tall bead on the intake rear to keep it from leaking. I have heard of several guys redoing there intake several times and end up with a leak until they got the right height and installed the intake perfectly. Are you able to tell exactly where it is coming from?

 

I used the Right Stuff sealer that comes in the cheeze whiz can. I also dremeled a trough in my intake and on the China wall of the engine block to hold a bead in there (last rebuild). That last part isn't really necessary, but it really works well. A lot of guys have had luck with the Right Stuff on the intake manifold leak - it is better for that gasket than RTV in my opinion, and I've used various RTVs for everything under the sun in the last 30 years, and although it will work, I think the Right Stuff is better somehow.

 

I can't imagine an intake leaking that much. IMHO, oil would have to be under pressure to leak that much, that fast. I would be looking for another culprit (maybe the oil pressure sensor-it's in that same area).

 

"it took two extra guys to stuff up the tailpipes with rags to bring the lambda down to acceptable levels."

Stuffing the tailpipes with rags is a significant blockage of the exhaust system. The exhaust has to go somewhere, in this case blow-by past the rings, which will pressurize the engine crank case. Oil pan gaskets, valve cover gaskets, etc. are probably leaking due to over-pressure condition as they are not designed for a pressure environment like a head gasket. As the exhaust gas escapes through the various gaskets, it brings oil with it, right past the gaskets. I suspect this is not something a gasket will "recover" from so likely to leak more and more each time you do this.

As a general rule, avoid mechanics, even emission test shops, that stuff rags up the exhaust.

 

Poor guy - emissions testing in UK - do what you gotta do I guess.

 

Reminds me of the good old days (pre-OBD), bring uncle Benjamin with you and the sniffer goes into a different car.

Not sure man-made blow-by is the best idea to divert exhaust gases; not sure what that does to the piston rings. You might be better off installing a cut-out and just opening that up a bit when you get there for the test?

 

I'm glad they did shove rags up my tailpipes, it worked!! I watched the lambda reading come down well into the specified limit and held it for the required 30 seconds. Before the rag idea came out it was just over and would have been a test failure and 50 pounds wasted for nothing. I had no choice but to let them continue as it would be illegal to drive my car until it passed the annual MOT inspection!

Of course I can't be exactly sure it is coming out of the manifold, but it sure is wet back there, its all over the egr pipe and has even run along and down the roof of the transmission tunnel above the bellhousing.
There does not appear to be any other obvious source, I was under the car as soon as I got home and all the floods of oil could only have been coming from the area at the back of the manifold/above the back of the heads.
I do find it odd that so much oil would come out of somewhere where not that much oil should be.
It really looked like I had thrown a rod or two under there
Maybe the oil pressure sensor is leaking, that's another thing I'll be looking at.

I'm going to take the manifold off again and investigate further, I might try the sealant compound you guys suggest if I can get it over here.
I was toying with the idea of using a strip of neoprene rubber sheet maybe stuck or screwed onto the "china wall" part of the intake. I have some 3mm sheet laying about that I could use - what do you guys think of that as a last resort?

 

No. Don't do that. The small block chevys had a cork gasket for that place and it never worked that well, the sealer works better if you clean everything really well and do it up right. When the cars first came out, a lot of us got the leak during the first year of driving, and got it fixed under warranty, But after that we figured out how to fix it ourselves. We also thought that the proximity of the EGR pipe from the header might heat up the back of the manifold and cause problems so we also tried to (carefully) bend that away or insulate it with fiberglass wrap. Most of us ended up removing the EGR and blocking it off, but if you have to keep it, maybe these tips will help you out. If you do try to bend it, be aware that there is a possibility that you will crack it, so be careful if you go that way.

 

All you have to do is install the intake and gasketing correctly and it will be fine. No reinvention needed. I would still get back there with some brake cleaner and clean up the oil mess, so you can better pinpoint the problem. I'm betting on o/p sensor or fittings.

 

I wanted to take a pic but the flash on my camera won't work so heres a short clip of the carnage back there.

[autostream]http://autostream.com/camaroz28/?page_type=firebirdplayerthumbnail&framepage=2551& transactionid=1330137626-8618040147&posted_by=CamaroUK_www.camaroz28.com&yo utube_video_id=CSBMuHAhfeo[/autostream]

This is immediately after an 8 mile drive earlier this evening, engine is at full operating temp but switched off for the camera. I didn't give it much gas on the way home cos i didn't want to provoke anything.
Looks like my previous silicone work has failed somewhat, but I agree on giving it a clean so I can see whats really going on back there.

It doesn't appeared to have leaked too much since the emissions test.

 

I notice the intake manifold above the sensor and beneath the EGR valve looks a bit wet, so unless the oil crept uphill I think you may be right.