Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Temperature readings: Diagnostic help please!

Good luck.

Looks like the answers are starting to reveal themselves. if when these items are replaced and if there is still an issue check out the water pump. If it has one of those plastic impellers they can fail gradually and limit the flow through cavitation or loss of drive. I think its the thermostat though, failing to have full range in opening and closing. If the O ring for the housing isn't in the pack and you want a quick try out, boil the removed seal in water... three minute egg style, if its undamaged and it should reform it to near original shape.

Test 1 complete: Thermostat removed and tested in a pan of water brought to the boil.

Good news: no sign of the inside seal breaking up, which is good because it might have meant bits of rubber getting into water ways in the engine or radiator.

Less Good News: No sign of the thermostat starting to open at 100C, and it should at least have shown a bit of a sign of moving if it's supposed to be fully open by 105C. Still, at least it does give a clear indication of a fault and I've got a new one due for delivery today.

Hamwich, I think that's good news, looks like you've almost cracked it. Thermostats can when starting to fail behave in strange ways often failing to respond to the correct temperature spec but also present with symptoms like they are becoming tired and after a dozen or so cycles the range of operation reduces until it fails. Now technically they are designed to fail in the open position but can't be relied upon to do so. I think yours is in the tired stage and isn't opening enough so the water temp has a slow constant rise until it registers as too damn hot! Mind you it'd done well and had a long life!

Yeah, it's easy to forget just how long ago 2008 was!

Oh yeah! and your thermostat has lasted longer than most cars do!

Update: Yep, it was the thermostat that had failed. Installed a new one and we're back to proper cooling.

That is good news. And the weather looks suitable for an extended road test.

Indeed it was. Although to do a proper test I did have to choose a very traffic-heavy route. It's stop-start stuff that gets a Morgan hot under the collar far more than blasting along country roads.

Excellent Hamwich! Now that's a good feeling isn't it! Fixed yourself and for peanuts too. Less than a garage would charge for a cup of tea while he looked at it.


Now that's true Morganering!!