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An overheating event, issues with cooling system and temp sensor/gauge.

439 Views 4 Replies 3 Participants Last post by  Boris_Kofler
Sorry this is an incohesive mess... important stuff is underlined, and the rest is the ramblings of a mad man.

There are two issues - overheating and the temp gauge.

(just as context - I don't have a working heater currently, the control valve is broken and I am waiting to replace it)

So, decided to take the '67 122s for a drive this weekend, its winter here, not stupid cold but not exactly temperate (48-50F). Noticed it warmed up a little quicker than usual but didn't really think much more of it, as I was taking a mate of mine for a spin.
For the three weeks I've been driving the car I have been really watching the temp gauge and there has been no sign of overheating.

Drove around town for about 30 mins then headed out to the country roads with no issues. We have got some decent hills around the area and after a particular hill climb
(TL;DR THE ACTUAL ISSUE STARTS HERE...) my temp gauge was leaning further to the right than... well, anyway... it was reading very hot. But it wasn't hot for long (max a few minutes) I popped the hood and found my expansion tank in two pieces... the neck had been separated from the bottle.
Limping it back to the petrol station (sorry not calling it anything other than that:rolleyes::LOL:), I noticed the temp gauge was only going to three positions, off the gauge to the left and to the right and bang in the middle. After filling up the radiator at the servo (its getting worse) and taping the tank shut I carefully drove home with seemingly little problem, 3 mile drive only got into the red on the last hill. The gauge sat a little hotter that I'd normally like it at but not too much of a concern.

At Home I started my troubleshooting.
The tape held the seal but the cooling system wasn't filled up completely.
First I removed the tstat. It was a rusty red colour and dry as a bone. tested it to see if it still worked and all seems good. Cleaned it off and dropped it back in. Could a tstat stick shut if its overheated?
Second, checked all the hoses for leaks nothing obvious.
Third, panicked and checked the oil but there was no emulsion in there, a little darker that I would have liked it to be but fine.

Here's my first* question If the expansion tank was already busted and came apart, say due to vibration, would that be enough to let the engine overheat due to there being air in the system?

On the replacement tank there's a collar that looks like its holding two parts of it together. As seen in the image below, there's a seam under the collar and crimping mark on it as well.
That collar wasn't anywhere to be found on my original tank
... (forgot to take photos of the old one before I plastered it with araldite, gaffer tape and a hose clap to keep it all sealed).

Second, would the cooling system be able to create enough pressure to take the top off the tank?

After sealing the tank with araldite (5min epoxy) gaffer tape and a very tight hose clamp around the neck (of the tank, not me), testing the tstat and refilling the radiator (not cleaning it out or bleeding it) I turned the key and waited for it to overhead again, but now the gauge doesn't move at all.
Can you cook a temp gauge? or is it that I need to properly flush and bleed my cooling system? ( I know the answer to that, but it could be something else)
As the heater isn't working can i still do a 'proper' flush of the cooling system?

So my third question is (cant count to save myself)... can I install any type of temp sensor into the same port as the original sensor with a second gauge under the dash? Because I'm not super comfortable driving without a temp gauge as the car is still new to me and I'm still learning what it sounds and feels like when running properly.

As a follow up If I get the electric gauge does it use the same port?

Has anyone done the conversion from Huke Basart? Seems like lots have said they were going to but there very little follow up in the different forums...

I apologies to anyone who actually read this through... I wrote it and I'm struggled to understand it.



Drinkware Font Automotive tire Artifact Gas

This is the new tank. On the original the neck and bottle seem slotted together, it didn't look broken it looked more like it came apart.
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Just in general the expansion tank holds the expanded water and allows back into the system as it cools down if the tank is leaking there won't be any coolant to suck back into the system so it will be low on coolant if it's so low the gauge sender is dry it will read low as it's sensing hot air
Did you dead head the heater pipes or connect together?
Most modern temp gauges are 1/8 npt so you probably need an adapter plug to step down the threads, alternatively cut the top hose and splice in an adapter spool that has a 1/8 boss for a temp gauge. Also take it to a garage and get them to test the coolant for exhaust gas it's a quick 5 min test if your head gaskets gone and your pressurising the cooling system that could be your culprit, not all head gasket issues show up as milk shake in the oil
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