I have a coolant leak that only shows up as the engine begins to cool down. I cannot see the origin. It appears to be from the block somewhere. On the forward left (driver's) side close to the end. Drips from behind the exhaust manifold (why I can't see it) collects on the lip of the oil pan and drips down to the v clamp on the exhaust where it drips off the bolt. I have replace the dreaded thermostat housing not long ago (along with all the hoses) and a quick inspection with a mirror under it shows it dry and tight. The water pump was replaced under warranty and also is dry (in case it was leaking around from the back). The block is dry on either side and I can find nothing from the top side that is leaking. Could a head gasket do this? In any event it does not appear to be coming from something I can change. The Haynes manual does not have a picture of the block with the exhaust manifold removed.

Any thoughts?

Thanks.

 

On an S, there is coolant that runs through the oil filter housing and to an oil cooler that is bolted to the housing. I don't know if there is coolant in this area on the non-turbo motor or not, but it is in the area that you indicate the leak is coming from.

On my car the seal failed between the oil filter housing and the block, and this resulted in an oil leak. Jack the car up, and look with a flashlight up the block to see if the coolant leak appears to be starting near the oil filter.

Mike

 

It's very near that area. Even if there is no line through the filter housing the block might have the port and the housing would just block it off. Something to look at.

Thanks.

 

I looked at realoem.com, and the gasket between the oil filter housing and block looks identical to the one that was leaking on my car. take a look at the diagram, and see if that makes sense.

http://www.realoem.com/bmw/showparts...29&hg=11&fg=30

Have fun,
Mike

 

Yes it appears the housing to block gasket set is identical between the base and S models which would lead me to believe the coolant passthrough from the block is the same. I have seen several articles on oil leaks from this gasket but didn't find any concerning coolant. Guess there's a first time for everything. Does appear that I will need to remove the exhaust manifold and Cat to get at it though. Have to decide if I want to do that or not.

 

Its probably a $600 bill for the dealer to do it. For my repair, the worst part was removing the heat shields, there is not much room to get in there. It was about 5 hours for me to do it the first time. It looks like less fun on the base engine, because it appears that the exhaust is solid from the tubes at the head to the v-band flange.

I would probably invest an hour into taking off the upper heat shield so that you can really see what you have got there. You may be able to get to the oil filter housing bolts without removing the exhaust, but I don't know for sure....

Mike

 

So here is a picture looking into my mirror to see what appears to be a hunk of the gasket sticking out by the top bolt of the oil filter housing. Never touched this area so it's been like that a while (100K) on the car. This would correspond to the location of the coolant passage. On the base model the down pipe is also the catalytic converter and it appears to be one with the exhaust manifold. I did actually remove the upper heat shield but the lower shield still hid everything with the Cat right there. Looks like your hunch was right though.

Thanks,
Bill

 

Well, at least you know more now. You can carry some extra coolant with you while you figure out if you want to tackle this or not. ECS tuning has been very helpful on matters like this, they can likely provide part numbers so that you can get an accurate estimate on how much $$ it will cost for parts.

You will also need to drain the coolant and plan on an oil change at the same time (in case any coolant got into the oil system). You should also plan on a new exhaust V-band clamp, yours will be rusty and difficult to get off. Realistically, you are looking at $100 or so in parts. I don't know if there are other potential repairs that should be done while you have the front of the motor apart, but now is the time...

Good luck,
Mike

 

Probably do a valve cover gasket too. There was quite a bit of oil in one of the spark plug wells when I did the 100k service. Since the cat is part of the header, the exhaust manifold gasket is also spot welded to the aft heat shield and is one component! Hope the header bolts come out freely. May do the O2 sensors as well, they don't last much longer than 100K.

Thanks for your help and insight.

Bill

 

Well that did it! No more drips. Thanks for the tip. What a job though. Took me all of Saturday. Putting the front end in Service Mode is a must as the exhaust manifold, cat, and down pipe are one and must be removed to get at the housing. I did hit the manifold nuts, upper O2 sensor, and pipe clamp with break free Friday night. Everything came apart fine, the manifold nuts are either red brass or copper plated (though no removal of the plating was evident on the threads) and broke free easily, spinning off by hand. The clamp was going to come off regardless with the pneumatic impact driver, but actually looked to be reusable though I had bought a new one. So a few things;
1) Even though I had drained the coolant by disconnecting the lower radiator hose, a lot of coolant came out when I finally removed the housing.
2) Definitely disconnect the battery, the lower exhaust heat shield is very close to the alternator battery terminal and must be wiggled out.
3) You will strip out a couple of the plastic fasteners holding the wheel well liners as well as break the plastic clips holding the fender trim on. Have some of those. That added two hours searching for available fasteners that would work on a saturday. I have a trim tool and that didn't help much.

I see why it leaks though. The bolt pattern on the housing is not spaced well at all leaving the lower side unsupported for almost the full length of both gaskets (oil and coolant). At 7 years and 100k the gaskets did seam on the hard side. I also replaced the valve cover gaskets and those seamed hard as well.

 

Glad you got it done and it is working well for you. Even though you lost a whole Saturday, it was probably worth the money saved by not having the dealer do it. Now you just need to make up for the miles that you lost by not driving on Saturday.....

Have fun,
Mike

 

Think I may be running into this very problem :( Replaced my thermostat at 62k, and am now on 73k with a very small coolant drip that i can't seem to source...Guessing it's this gasket :(

 

Sounds like it could be the pipe between the pump and thermostat housing, both mount against the mid-pipe on both the pump end and the thermostat end. If it leaks on the thermostat side it usually leaks down the pipe which makes it difficult to pinpoint.