Issue with car overheating and then righting itself

plasticpaddy74

First time using so apologies if I’ve not followed protocol. When I drive my car it will get up to temperature and then shortly after will start to go past the mid point on the car. This will continue until I either pull over or go easier on the accelerator and then will usually be fine for the rest of the journey (usually we’ll over an hour). Has anybody seen this before and if so what did they do to fix it. I’ve had 2 of the electric pumps in the car changed already and no joy. I have a video but it’s too large to upload. Any advice would be appreciated.

MakersMark

Could it be a sticking thermostat?

BlakeS94

Make, model and year of car?

Sounds like a thermostat on the way out, it's starting to stick in the closed position which would explain the overheating then it opens and stays open (as it should) while the car is running for the rest of the journey which would explain why it stays within operating temp for the remainder of the journey.

I would keep a close eye on your coolant levels regardless, it takes a very short time for an overheating engine to do a lot of damage.

mikewest

Car make and model please. I used to have this problem on a old BMW E39 if the coolant was drained and the coolant system not bled properly afterwards. An air pocket used to form near the temp probe. It was not a big problem but was very annoying until fixed.

plasticpaddy74

Skoda Octavia VRS 2017. I had said that to the mechanic and he said unlikely but I suppose it would be worth a try to change it and see what happens. He doesn’t seem to be able to pin point the issue as no errors showing up. Thanks for your responses, much appreciated.

cml387

I'd do a pressure check on the cooling system. Definitely keep a close watch on the coolant levels.

John.G

You say that you replaced two electric pumps. The main cooling pump is belt (probably timing belt) driven but has a electronically controlled sleeve that can stick and cause the problems above, was this one of the pumps that was changed?

plasticpaddy74

That pump hasn’t been changed yet, I have a guy looking at it next Monday. I’ll certainly mention that to him as well. Thanks

Mech1

VAG coolant temp sensors wouldn't be known as the most reliable.

jmreire

Not saying that its what is causing your cooling problem, but the radiator expansion tank in the Skoda's have a well known problem where the silicate bag located within the tank, split's and leak's silicate directly into the coolant, which then circulates throughout the system and causes major problems when it clogs up ( especially the heater matrix) Check the plastic tank and see if it has "MIT SILIKAT" written on it. If it has, then its a possible cause. Like several posters have already said, I'd be thinking thermostat problem.

mickdw

Given the car you have id go straight to the main water pump. As mentioned above, the pumps have a cover that moves to give the pump a variable performance.

All great for efficiency but seem very common fault on the those.

teediddlyeye

I'd put money on it being the main pump with stuck sleeve. Common as fcuk.