Help: Leaking coolant - only when engine is cool - from behind oil pan .......

[ReubenG]

81 diesel 1.6 ; recently replaced water pump, t-stat, radiator, and hoses. Drips coolant from behind oil pan, seemingly only when the engine is cool... I can't tell where it's coming from, but it definitely doesn't appear to be any of the hoses, or the radiator, or the water pump 

[vanbcguy]

A freeze plug would be my first guess...  There's 3 in the back of the block below the exhaust manifold.

[theman53]

When you did the water pump did you replace the housing or just the pump. If you did the housing I could see it leaking from the o ring to the block and running around the block to the back...if it wasn't leaking before you did all the work.

[ReubenG]

I never touched the freeze plugs....would they begin to leak for some reason after performing this maintenance? -- as for the pump, yes I replaced the entire housing too, with new o-ring, but it doesn't appear to be leaking from there. I'll take a closer look, but I think that's ok.

[vanbcguy]

Sometimes things have been happening for a while but until you start checking things over after working on them you don't notice.

Freeze plugs for instance can be weeping for a while and then once you flush the block and knock out the scale and rust that was sealing them, a small weep becomes more significant.

Easy enough to check either way. If coolant is coming from the back of the engine there are only a very few possible sources.

[smutts]

Dying head gasket is also a possibility, drove me mad trying to find mysterious leak behind the block (no coolant pressurisation), until the thing blew properly 9 months later.

[ReubenG]

Yes, it's definitely the freeze plug(s) --- One of them has a rubberish extension coming off it and coolant is pouring out of there. What is this? Also, the block heater is there, and possibly leaking a bit. Tips?

[ORCoaster]

Remove and repair.  two tips no charge

[vanbcguy]

Yup. Knock em out, hammer in new ones, done. If you don't use / need the block heater you can replace it with a normal freeze plug.

[ReubenG]

...I saw a youtube video where a guy used part of a channel lock pliers to wedge them out, see here: https://www.youtube.com/watch?v=MlK321GS94U

thoughts?

[ReubenG]

can I replace the core heater plug with a regular freeze plug?  any DIYs on removing the plugs? THANKS

[vanbcguy]

Yes, absolutely.

[ReubenG]

Lucky for me it was only the core heater that was leaking and not any of the freeze plugs. Took 5 minutes to remove the old heater plug and put in a new one. ... then refill cooling system of course. Thanks!

[smutts]

One of them has a rubberish extension coming off it and coolant is pouring out of there. What is this?

Could be the turbo coolant return hose, at least that is how it is on the SB & RA engines.