Gaborr

So I've done a bit more troubleshooting about this issue. Had a look inside the cylinders to see if any coolant can make it's way into the combustion chamber. I've done so using a not so great endoscope, despite the not so great picture quality I can't really see any coolant in there. Cylinder 1 - Cylinder 2 - Cylinder 3 https://imgur.com/XgXQSR4 Also performed a coolant gas test. This one was a bit inconclusive. The liquid turned green but not yellow, which basically means either there is a small leak, or it was exposed to heat. Fluid turned green at around 5 mins, which is supposed to be the max length for the test. So I'll have to redo this test this week. Initially I thought that the the way the fluid is being pushed out is due to the exhaust gas coming through it. At the same time if this much exhaust gas is coming through I would think that the test would be a conclusive fail, so this is most likely just air? Checked the thermostat as well and it opened at the correct temperature. Another interesting behaviour I've noticed is when I was bleeding the car, the temp wouldn't raise when idling, only when the engine was revved, and then when I stopped revving it fall back down. Should the car warm up just by idling? Lastly when I was driving around, the teperature would go up slightly from the middle, then it would drop down, then again slighlty go up. It was unrelated to load, it wasn't overheating more when I was accelarating more. I'll do another coolant gas test and if it comes back negative I'll take the water pump out to see if it's damaged, and try to bleed out any air that is in the system.

Yeah that makes sense that a blockage wouldn't cause bubbling but I would assume if combustion gases leak into the coolant lines then once the car cools down the expansion cap would release the excess pressure once opened but it doesn't seem to do that. Unless the built up pressure leaks back into the combustion chamber? I'm not sure if that'd be a possibility.

Yeah the cold radiator and lower hose combined with the pressurised upper hose sure sounds like there is a blockage in the radiator. I'm unsure in what fashion would the pump fail. I was thinking that the temp going down when the engine is revved could be due to the impeller being able to spin up on the shaft. But thinking about it now it could also be that the water is now able to flow past the blockage with the increased rpm? Im fairly certain water didn't freeze as I haven't topped it up by that much.

Hello everyone. I've got a mk1 with the 1.2 HTP 12V engine and I've been having some issues with overheating and I'd appreciate some help with diagnosing. I'll list the events that led to this point in chronological order and put some more points below. Car was initially just loosing coolant slowly but the temp gauge sat steadily in the middle - >Assumed the HG had failed -> garage checked compression and checked for leaks and they found none and compression was ok- > replaced coolant cap - > lost some more coolant - > garage put some leak block in the coolant. Issue seems to be fixed. Then the winter came and the car had not had heating for a while, I've checked the heater core pipes and one was cold the other was hot. Ive asked the garage to flush the heater core, they said the thermostat was faulty and replaced it. The car had heating but then on the way home it overheated out of nowhere. Went back to be flushed and bled a few times, but the issue never went away. The car wouldn't overheat when idling in the garage but after about 30 minutes of driving the temp gauge would start creeping up. The current symptoms of the car: - temp gauge sits in the middle for about 30 mins then car heats up fairly quickly - top radiator hose hot and hard - bottom hose and radiator are cold - fan doesn't kick in - no heat when the engine is idling, heater blows warm when the engine is revved up. - when the temp starts going up, stopping and revving the engine bring the temp down quickly. - The morning after there is no pressure in the expansion cap, however the coolant goes above the max level. - car doesn't smoked white and is not loosing coolant. I'm quite lost as to what could this be, airlock, failing water pump, blocked radiator, or the headgasket failing? Here is a video I took when I was checking if the water pump is circulating properly. I'm not sure if that bubbling is normal or not. https://youtube.com/shorts/S3dUrjo3o8s?si=4qLkDUg6XXwZk_bI If anyone has any input on this it would be greatly appreciated.