TR4/4A Coolant pressure

A year, or less than two thousand miles, after a rebuilding my engine the coolant is pressurizing and running a high temperature. I run Evans waterless coolant in both my cars and no Issues with the TR6 so I know that the coolant is ok. Evans should not build pressure so something is not correct. I am starting to think a little outside the box and wondering if in the rebuild, or since the subsequent head gasket change, that there maybe combustion gases finding a way into the water jacket but whatever path it may be taking is tight enough that coolant is not leaking back into the cylinders.
I will pull the head and check a few things but anyone got any ideas on what it could be?

Sure, I fought similar symptoms for a long time. Your head gasket is leaking, but only against the very high pressure of combustion. Probably even only at full throttle. No coolant back into the cylinder, as it's only under a few psi of pressure. And no drop in compression as shown by a compression test.

There's a simple test to check for the presence of combustion gases in the coolant. Before pulling the head, suggest either buying the tool or having a radiator shop do the test for you.

In my case, the main problem proved to be insufficient liner protrusion, only on one side! Apparently, the liner seats are not exactly parallel to the top of the cylinder block. Rather than go through the hassle of having the block remachined, I came up with a band-aid of adding a ring of soft copper wire around each cylinder. I originally only intended it as a stop-gap measure, but it worked so well that I probably never will get the block remachined. YMMV and all that


PS, here's an example of the test for combustion gases

Supposedly Autozone will loan you the tool, but I haven't tried that. I picked up a used one for $10 on eBay, plus another $10 for a new bottle of indicator fluid.

Randall
thanks for validating my theory, some LBC colleagues thought that I was way off base. I agree with testing before any disassembly especially as I need to understand the “what’s and the whys”. I will buy the tester and update this thread. I was starting to think that it may have been related to the liner installation.
Paul

There is also a home-made test I have used but it is revealing only if the combustion leak is also occurring at idle or high idle.

You can fit a rubber glove tightly over the open neck of the radiator - a combustion leak will inflate the glove. Best done with the engine already warm so you are not fooled by normal expansion.

For added excitement you can substitute a commonly available latex product sold at your local pharmacy.

I can confirm the soft copper wire soldered to the head gasket will fix your coolant pressure problem, it worked for me.

Graham

Thanks Graham.

Paul