Last ditch temporary fix for cracked head

Well I hope its a cracked head but it could be something else like a bolt or worse. The car runs and runs fine, up until it starts beeping and overheating. Then I have to pull over and wait for it to sort itself out. The bonus of water less coolant, it is drive able┬áto a safe spot to stop and if left running doesn’t go off the scale, but rater slowly lowers the temperature after a few minutes. If I just turn it off I end up with a hot spot and local expansion and fluid loss if in unlucky.

One solution over the years has been to take the thermostat out completely and I have found that on a number of old cars I have driven. This does tent to solve one problem but causes many more. Increased emissions, longer for the car to warm up, if it ever does, lack of power.

Some racers replace the thermostat with a restriction plate, basically a disk with a hole in it. But there engines run hot anyway and its not for hours at a time.

After a lot of research I settled on the drilling option.



A bit of tape ( masking would be better) and a 6, 4.5 and 3 mm metal drill bit.

The holes are there to try and stop the car going to overheating. The usual trick is to just remove the thermostat, but its there for a reason to keep the engine at operating temperature. The problem comes when air builds up behind it, it doesn’t conduct heat well and the thermostat thinks it need to close, then more builds up and the system overheats. The holes let the air escape much faster than that tiny little jiggle hole. Plus there is always some fluid getting to the radiator to be cooled. Without this fix it doesn’t matter how good your radiator is, if the fluid cant get to the rad it will stay too hot.


Be careful not to foul the mechanism or cause a leak and make sure the holes are not blocked by the housing. I made 2 4.5mm holes and 2 3mm holes. Then deburred them with a 6mm drill to remove the sharp edges and any loose metal.

Explaining the hole in the top of the bin to the wife was the hard bit…

So, the result. So far I have not seen any difference, temperature seems fine, warm up is no different although its not cold out anyway. I have a few long drives this week so we shall see……

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