I know this is a 75/ZT forum, but as a number of members have an MGF or TF as a second car, my recent experiences might prove useful to them (and could even stop a perfectly good car being wrongly diagnosed with HGF
).
Some of you will know that 12 months ago I changed the head gasket on my better-half's MG TF. I followed all the instructions; measured liner heights to block, tolerance between liners, head straightness, correct gasket (Payen), new bolts, etc, etc. but ever since, the header tank has continually lost a tiny amount of coolant every few weeks
I've since pressure tested the system both hot and cold with the car on a ramp, but there has never been the slightest visible leak anywhere to give a clue as to where the coolant's been going.
Now, the other day I got in the car after it had been sitting in the sun and noticed that it was very humid inside, so my thoughts jumped to the possibility of the heater matrix leaking ? Lifting the carpets, I found the sound deadening to be damp near the middle of the car, next to the central tunnel, but bone dry next to the doors (where you'd normally expect it to leak in)...
Having removed the wet material, dried the floor and armed with talcum powder, I traced the source of the dampness to the seams along the edge of the tunnel which also contains the two steel pipes bolted to the drivers side which take the coolant to & from the matrix, from the engine bay. So after much disassembly later, I eventually found that one of the pipes had a tiny rust hole in it's upper surface and a hairline crack at one of the supporting bracket welds.
The problem is that the leaks were really very small and all the lost fluid was soaking into the underfelt, with no apparent signs to show this. Hence, anyone trying to find the fault would likely assume that being a K-series, the loss was being digested in the cylinders from a faulty HG repair
Most owners will by now be familiar with the two underfloor pipes which run to the radiator (yours may have already been replaced with stainless, as these get attacked with corrosion from both inside and outside, due to being located outside the body) but the heater pipes are internal so only rust from the inside out and may only now be starting to show up as a problem. I have to say they are a complete b**t**d to replace, with most of the interior needing to be removed to get them out, a ramp is also very handy when undoing the little, rusted bolts on the closing plate in the engine bay, but it can be done. I'm pretty certain they were slid in from the engine bay end at manufacture, before the engine & subframe were ever in position, so replacement from inside the car (leaving engine & gearbox in place) is a lengthy job, albeit possible if determined
So if you have an F or TF with a slight but continual loss of coolant, just lift the carpet and check if it's wet near the central console BEFORE taking the head off
If anyone needs any advice on the process, please just ask
