Serious overheating, please help!

[TBK]

Hi, newbie here,

My X-reg 6N2 has recently started to overheat badly.

Started with the coolant temp sensor dying. I replaced it, but after one journey, the car started to overheat.
Initially, the gauge would rise almost to the top and then drop to about middle.
Now, the gauge will rise very very fast right to the top and stay there. Decided to renew coolant and thermostat today, but the problem persists.

Any ideas what the cause might be and what I should do next?

Cheers.

[alexperkins]

Blocked radiator or more seriously a failed or failing water pump. It's not unusual for the impeller blades to snap off and the water to pretty much stop circulating

[TBK]

any way I can easily check the operation of the water pump?

[alexperkins]

See if water is flowing back into the top hose that goes into the coolant tank at a good rate whilst the engine is running

Also if the coolant hoses heat up fairly quickly after starting the engine

[TBK]

Cheers Alex, I'll have another tinker tomorrow and come back with more info.

[TBK]

Hi Alex,

Not had a chance to tinker today but had a play in the morning to see exactly how the car behaves;

From complete cold, gauge read cold as expected.
Turned on the engine, gauge remained cold for about 1 minute (almost thought that everything was back to normal).
Gauge jumped immediately to mid position, checked all pipes and all bar rad hoses were lukewarm.
Gauge then dropped to near zero a couple of times before sitting back in mid position.
After a couple of minutes gauge started to rise.
All bar rad hoses were quite hot. Top rad hose was hot up until half way where it was cold. Bottom rad hose was also cold.
Before long, the gauge was right up to the max with a flashing warning light.

Checked the fuses and looked ok.
Fan was spinning freely.
I also squeezed the the top inlet pipe going to the expansion tank and could see I was stopping the flow of coolant back into the tank. So I'm assuming the pump is working (or at least barely).

Something I didn't check was the inside of the thermostat housing properly. Read that this can break and not allow the thermostat to open.

What do you think?

[alexperkins]

I would suggest flushing the radiator through. Sounds it might be blocked

Also check the inside of the thermostat housing

I wouldn't rule out coolant pump failure

Are you losing water at all?

[TBK]

Ok, I'll try to flush the radiator and check the thermostat housing at the same time.

Coolant level went down a little while I went on a quick 5 min drive yesterday, assumed it was due to some air pockets clearing after I refilled the system. Didn't seem to drop this morning.

[alexperkins]

Just be aware it could be head gasket if it drops again