M42-Help me guess the location of this coolant leak!

[dblmikeusa1]

I have a coolant leak coming from somewhere...

Here is what it is doing... Leaking from above, at the backside of the engine bay. Coolant is rolling down the passenger side of the transmission and dripping from the point where it meets up with the engine, making tracing the starting point difficult.

I have tried to feel around the coolant hoses at the intake area, but have not found anything...

Any ideas?

What makes this even weirder is it does not always leak... it is random and when it does leak, the puddle size is usually no bigger than a silver dollar.

[ansonivan]

The m42 uses a plastic coolant flange on the back side of the head, the plastic degrades over time and starts to leak. There are two coolant hoses (heater core line and a small diameter line whose purpose I can't remember at the moment) which attach to said flange are also common leak sources.

It's a nasty tight area to work in (that's what she said) so unless one or more of the components in question have been replaced recently I would recommend replacing the flange and both hoses all at the same time.

[dlmrun2002]

After an engine rebuild and install I had a similar leak on the back of engine dripping down tranny. I re-tightened some hose clamps on a few hoses and that did it. I think it was hoses on the heater check valve.
dlm

[gearheadE30]

I'd pull off the upper intake so you can see in there better. My first guess would be heater plate mess or the plastic hose with the coolant blowing back onto the tranny. The heater core hoses are in the wrong place to leak there, but the check valve might do it.

Out of curiosity, what is the purpose of that valve? It seems like it might make the engine warm up faster by diverting coolant, but I can't really tell. I actually took it out when I did the hoses because the new ones didn't have a place for it.

[KenC]

My guess is going to be the huge mess of coolant hoses between the head and firewall. One or more of them is probably cracked and leaking. Definitely a tight area to work in, but doable with a stubby flathead and/or finger-ratchet and some patience.

[dblmikeusa1]

The m42 uses a plastic coolant flange on the back side of the head, the plastic degrades over time and starts to leak. There are two coolant hoses (heater core line and a small diameter line whose purpose I can't remember at the moment) which attach to said flange are also common leak sources.

It's a nasty tight area to work in (that's what she said) so unless one or more of the components in question have been replaced recently I would recommend replacing the flange and both hoses all at the same time.

Ugh... I have tried searching the pics at www.realoem.com but I am not sure where this part is you mention...

Is it where hose 23 attaches to the head?

[ansonivan]

Sorry, I was thinking of the m44 which uses the plastic flange on the rear of the head.

[dblmikeusa1]

for the record... it was hose 23 that split on the topside just aft of the connector. Coolant was collecting in a small area below that and when I would pull into my driveway from a certain direction it would run down. I finally got to it when the hose decided to finally split completely off causing a nice rush of coolant to go everywhere.

[Beach Bum]

I do love it when someone comes back with the solution to a problem. I hate seeing unfinished threads.