Oil leak on front of engine

[twistedtree]

I've got a nasty oil leak on the front of one of my engines.  The real gusher of a leak was due to a missing socket bolt holding the PS pump bracket to the upper oil pan.  I fixed that and it stopped gushing, but I still have a persistent leak somewhere in the front.  As best I can tell it's origin is behind the water pump, in the lower area where the pump nests into the scoop-out in the block.  I can see the upper part of the pump housing a little bit in that area and it looks dry, but the lower part, especially around the alternator adjustment arm mount point is wet.

From what I've read I think the possible culprits are:

1) The small head bolt who's tap hole extends through to behind the pump housing.  I checked this today and the bolt is present and tight.  Also, I'd expect the top of the pump housing to be wet with oil if it were coming from there.

2) The pins that retain the chain rail could be leaking.  I believe this engine was worked on and recently reinstalled in the car, but not run more than a few minutes if at all - otherwise the gusher of an oil leak would have been tracked down and fixed.  I'm thinking maybe these pin heads were not sealed when reinstalled?

What else could it be?  I've looked at a disassembled block and it looks like the two guide rail pins, the head bolt, and one of the water pump bolts are the only ones in that area that pass through to where there's oil.

Any other ideas?  My goal is to only take the whole front of the engine apart once.

Thanks,

Peter

[ja17]

Hello Peter,

Start by checking for the small bolt in the chain gallery. You will need to take the valve cover off.

[twistedtree]

Joe,

Yes, I checked that today.  The bolt is there and tight.  I was hoping that's all it would be, but it doesn't look like luck is on my side with this one.

[ja17]

If your car has AC, any of the bolts going into the block can leak oil.  Also the power steering bracket at the block is also a source of leaks. Check the metal banjo fitting for the injection pump oil line also. The chain tensioner leaking on the outside of the block (under the thermostat housing) can also be the cause of a leak.

[twistedtree]

OK, thanks.  No AC on this car.  I luckily have a stripped block lying around so I can inspect the various bolt holes and see which penetrate the block and are potential sources.  I'm mostly trying to narrow it down as much as possible while I can still run the engine and check for leakage.  Once I tear apart the front, I won't be able to test any repairs until it's all back together again, and I can't count on the source being obvious once I get things apart.  If there is anything I hate, it's having to do a job over again.

[twistedtree]

I had an epiphany today, at least I hope so.  You know that little head bolt that hides in a pool of oil and is subject to leaking down behind the water pump?  Well, when I pulled the valve cover the other day to check it, the bolt was not in a pool of oil.  I could see it just fine.  I though nothing of it at the time, but today it occurred to me that the pool of oil must have gone somewhere, right?  I don't think there is any way for the oil to get out of that little pocket other than past the bolt and down around the back of the water pump.  I think I may have found my leak after all.

[twistedtree]

I wasn't so luck.  I left the car for a month and when I returned there were a couple of puddles on the floor 

I removed the valve cover and once again found the little pool with the bolt in the bottom in the chain gallery empty.  The only place for that oil to go is down past the bolt, so I set about removing the bolt to reseal it.  On removal, I found a lock washer under it, which doesn't seem right for a bolt hole that needs to be sealed.

What should be under the 6mm allen bolt?

1) A lock washer?

2) A flat washer?

3) Nothing?

Either way I'll put sealant on the threads of the bolt, but I'd like to also get the right washer under the bolt.

Thanks!

[Jordan]

Peter, do you have a picture showing what it is you are talking about and where it is exactly?  Thanks

[twistedtree]

Not at the moment.

The front of the head has 4 small bolts that help seal up the timing chain gallery.  These are in addition to the 14 big head bolts.  The right-most bolt is inside the chain gallery under the tensioner.  The head casting is such that oil pools in the area, submerging the bolt.  There is probably 1/4 to 1/3 of a cup of oil in the pool. You have to know the bolt is there or you would never find it.  The hole that the bolt threads into in the block often passes all the way through and emerges outside the block over and behind the water pump housing.  If this bolt is left out or not properly sealed, oil will leak down behind the pump housing and all over the place.  Because of it's location, it is often assumed that the front crank seal is leaking when it's not.  I know all this only because of this web site.

I'm pretty sure this is the source of my leak for a few reasons:

1) My leak only happens over an extended period of time with the car sitting.  Things like oil seals don't keep leaking when the engine is shut off.  The source needs to be from some standing pool of oil.

2) The pool in the chain gallery is empty when it should be full.  There is nowhere else for it to go except down the bolt hole.

3) The engine is wet all around the right front of the engine.

4) I can't believe the bolt should have a split lock washer because it will always be subject to leaking.  My assumption is that there should be a flat washer or no washer under the bolt.

Hopefully this is clearer, and I'll try to get a picture later today.

[Naj ✝︎]

Hi, Peter,

2) A flat washer under each of the 4 bolts

Naj

[twistedtree]

Awesome, thanks Naj.  I sure hope this stops the leak.

[Naj ✝︎]

Hi, Peter,

The DIN part # N 000433 008406 for these washers would suggest they are ordinary 8mm steel washers.
The other head bolt washers have specific MB part #s.

Naj

[ja17]

As a general rule, you will find that factory does not used lock washers in direct contact with aluminum parts. There may be some rare exceptions.

[Naj ✝︎]

Hi, Peter,

The bolt in the oil well sits on a ledge. If your resevoir is completely empty, consider changing the 'O' ring seal on the chain tensioner. They get well roasted and leak as well.

Naj

[twistedtree]

Excellent pictures.  I'll double check the tensioner, but my recollection is that it appears dry on the outside.  Unfortunately it will probably take several weeks to determine whether properly sealing the bolt solved the problem.  Last time when I tightened it, there were no drips after several days and I thought I had fixed it.  But after 4 weeks there was a puddle.

[gvillayandre]

Hi,

I have the same problem.

It seems that oil is leaking from the timing chain tensioner.

Do I have to take any special care to change this O ring

Thanks in advance.