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Mystery Oil Leak on Back of Engine


jonboyb
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This is on my 2.6 Raider but nothing different out back. When I got it the PO warned of an oil leak that would leave a drop or 2 when parked. He was 100% correct and truthful. Like clockwork it leave a few drops after parking. The engine is REALLY close to the firewall in the Raider/Montero so not alot of room to feel around but a flashlight reveals the firewall to be a little damp behind the head and the top of the bellhousing is just nasty from years of the seep. However, I've now done a headgasket, new cam packing seal, and new VC gasket and RTV in the corners around the cam cap. It's BONE DRY on the back of the head. However, the same few drops when parked and the firewall damp from head level down (about the block surface elevation).

 

There's no oil plugs on the back of the head or engine in this area (there is an oil gallery plug in the back of the block but it's under the bellhousing so no way it's leaking that high). There's also no oil pressure along the back of the engine (all drainback galleries from what I remember) so how the "H E Double Hockey Sticks" is oil spraying onto the firewall. Even if the headgasket were leaking on the back, the head cracked back there (which it isn't), or even the block cracked on the back.....there's no PRESSURE to spray oil over to the firewall. Any ideas???

 

On another note I've been daily driving it for 2 weeks and no oil has been needed to topoff so the leak is very minor....however, leaks irritate me and I hate driving a vehicle with one.

 

http://i954.photobucket.com/albums/ae29/awb1102/BackOfHead.jpg

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No....leak is still there for sure 100%. I degreased the firewall and it was wet again after a couple hundred miles. On another note, the sides of the engine are bone dry so it's not leaking elsewhere and blowing back. Edited by jonboyb
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Yeah Jon,

 

The only thing I can think of is the rear cam cap. I usually put a small line of sealant around it. They are one use only as the rubber seal is a crush type seal. Now in saying that, I have used one twice and it didn't leak but ya never know. It will also leak around the corners of the valve cover gasket onto of the cam cap. I always put a dab in the corners there because the valve cover gasket doesn't match up perfectly to it.

 

Might be worth pulling the valve cover off to check.

 

Lance

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Valvecover has already been off twice with a new cam packing seal with a RTV skim coat and RTV in the valvecover corners. She's bone dry on the back of the head. I've built probably 40 of these engines since the early 90's so anything "normal" has certainly been checked...LOL :) This is going to be a weird one.
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lol, I am with you. Prolly a microscopic pin hole clean through the back of the casting that you will never find. lol. I hate oil drips tho, I am with you. Almost need to set up a micro video cam in there and watch it while you run.

 

Good luck and let us know what you find.

 

L

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How about the oring around the tin plate for the upper balance shaft or its bolts.

 

There's a hose off the valve cover for the crankcase pressure even on an n/a engine. What did you do with that?

Edited by Indiana
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Leak is south of the valvecover for sure. Just pulled the VC and rocker assembly.....again......to inspect that back area and put in another cam packing seal. There appeared to be a tiny bead of oil where the rear cam cap bolts to the head (see picture below on old head). Now that little area SHOULD be a machine fit with no RTV needed but it was the only sign of oil period along the back so I put a thin skim coat of RTV there before bolting the rocker assembly back in. Fingers crossed.....giving the RTV a couple hours to set then off driving again.

 

Note....I'm actually talking about between the 2 aluminum surfaces...not in the corners where RTV is supposed to go.

 

http://i954.photobucket.com/albums/ae29/awb1102/BackOfHead2.jpg

Edited by jonboyb
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If too much sealant is used on that rear plug, as in trying to seal up an old used one, when you tighten down that cap the sealant oozes under the cap making a gap you can't seal. That will also not provide the correct bearing journal for the same. Oil will seep from the gap under the gap if that happens. The plug has a shallow depression groove and only a very small amount of sealant should be used there.

 

Some rear plugs look like a cap, some look like as they are shown in this picture. Get a new plug and just put on a thin film. The plug seals into the head because its coated in silicone and has a soft outer surface but the film of sealant you apply is to keep the oil from leaking not to keep the plug from coming out.

 

http://www.b2600turbo.com/images/1d75.jpg

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You ever feel like you can't win for losing. Can't get it to produce a drop of oil now.....but a lifter has decided to be noisy :mad: I bled them and checked them since I had the rocker assembly off. Going to give it a few miles and if if doesn't quieten down off with the VC again....LOL. Car has excellent oil pressure too so no reason a lifter shouldn't pump up.
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Wow....this one just got weirder. I let the car run for over 30 minutes including a drive and never got a single drop. Came back out this afternoon and the same little spot was there....WTH. Cranked her back up and let run FOREVER....even at revs to keep oil pressure up and no drips. Turn the car off and immediately get a few drips. I'm totally confused now. Doesn't leak a drop running or driving but as soon as I turn it off the drips start...and still can't tell where it's coming from. Confirmed this several times throughout the day. It's so grimy that I'd have to pull the tranny to do a real degreasing of it so tomorrow I'm buying some UV oil dye and going to test it with my trusty blacklight. Never used the dye before but have several buddies who swear by it.....most find their leak in minutes.

 

The only leak I could think to fit this bill would be the oil pan when the oil drains back into the sump once the ignition is cut.....but this is definitely not from the pan....it's clean. The drips always come off 2 tabs on opposite sides the side of the tranny......like it runs along top of the bellhousing (which the grime confirms)

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  • 7 months later...

Sorry to pull this thread out of the grave, but I have the exact same symptoms. Did you ever figure it out?

Would you say its a strang leak??

 

Headgasket?? Trans input shaft seal??

 

-Robert

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