Thread: Got the old girl hot.....quick!

Originally Posted by Mercguy

When you first did the flush, did you have the heater on full?

Just have to ask as it wasn't previously mentioned.

They don't have a heater tap, constant flow through heater core. So heater on or off make no difference really.

OK, its still getting hot, loosing coolant through the expansion tank overflow. Heater was partly blocked. had a measured 12L of coolant added. Cap is new. Check its full, drive 50km and its all ok. Stop, cool down and drive another 50km and its pushing coolant out the expansion tank cap. Only leak i can find is via tank/cap. Floors around heater are all dry.Run it up to temp and shut off and it will hold pressure till it cools again (without loosing coolant).

Looking at parts diagrams online, it appears i have the heater hoses from the back of the manifold to the heater core the wrong way around. Would this create a stuborn airlock? Heater seem to work ok now.

Can a dodgy head gasket pressurise the system enough to loose coolant, without putting any telltale bubbles into the coolant?

Its starting to get a tad irritating

Sounds like quite a few old 3.5's with tin head gaskets that I've come across. The gaskets don't tend to blow out big chunks like the composite ones, but let compression gases into the cooling system under heavy load. If you modded the header tank to avoid bubbles being trapped in the top of the radiator you might get away with it, but new head gaskets would be wiser. The heads are probably even tolerably flat, I certainly didn't have to skim the heads in the 3 old 3.5's that I put new head gaskets on.

Mite give that mod a try. Motor was rebuilt at around 325K, its now got about 610k on it, so a leaky head gasket would not really be a suprise i guess.