Golf mk2 Gti

[Jarred]

So how do you know it's overheating?

I'm with Paul on this one. Why do you think it's overheating?

[Schalke04]

I'm with Paul on this one. Why do you think it's overheating?

It's overheating because I can hear it boiling the water & it's coming out of he expansion tank cap. I've replaced the cap and it still does it.

[Jarred]

do you have a o ring on the expansion bottle? iirc some are meant to have them, some aren't.

The bottles are designed to have a natural overflow in them, and when you overfill them, the level automatically sorts itself out. is it possible that's all that's happening? What happens after the water has gotten out, and then the car is left to cool (ie, overnight). Do you come back to find that the level is ok? or is it low? Does the expansion bottle have a level indicator on it, factory and good OEM ones will, but some won't, and it's easy to overfill them.

[Schalke04]

do you have a o ring on the expansion bottle? iirc some are meant to have them, some aren't.

The bottles are designed to have a natural overflow in them, and when you overfill them, the level automatically sorts itself out. is it possible that's all that's happening? What happens after the water has gotten out, and then the car is left to cool (ie, overnight). Do you come back to find that the level is ok? or is it low? Does the expansion bottle have a level indicator on it, factory and good OEM ones will, but some won't, and it's easy to overfill them.

No o ring on the expansion bottle. If I open the expansion bottle when the car is warmed up it's got boiling water in the expansion bottle. Coolant level seems to drop when I leave it but I can't find a leak anywhere. It's doing the same thing my 1.8t did with a failed water pump except this water pump was clearly spinning and has no sogns of wear, the other spun freely. It's not just leaking out a bit it's basically emptying all the water once the cars warm.

[golfmeup]

Does sound odd.
What condition is your radiator?

[Schalke04]

Does sound odd.
What condition is your radiator?

Well radiator was on a car that over heated because of a failed water pump. Did have a lot of gunk in the system but I hosed the whole system out to clear it and it seemed fine.

[golfmeup]

Just a thought- as this car has overheated before, it may have had stop leak put in the system by the previous owner, it could be causing some blockage in the flow somewhere.
Do you have a spare radiator handy? Might be worth doing a trial fit and see if same results.

[Schalke04]

Just a thought- as this car has overheated before, it may have had stop leak put in the system by the previous owner, it could be causing some blockage in the flow somewhere.
Do you have a spare radiator handy? Might be worth doing a trial fit and see if same results.

Well as fast as the hose was putting water in the water was coming out, so don't think rad Is blocked. It's got my old engine and water pump and that was fine before I took it out. Thinking it's airlock

[sports racer]

Sounds like you are loosing water through the expansion tank which is normal. If the tank is full when cold it's going to loose water as it heats up because the hotter the water gets the more it expands. When it cools down it contracts and you think something is wrong because you're missing some water.

If you don't keep filling it up each day it should still have some water in it after a few days. If it's overheating you should also be losing power when it's hot.

[Schalke04]

Sounds like you are loosing water through the expansion tank which is normal. If the tank is full when cold it's going to loose water as it heats up because the hotter the water gets the more it expands. When it cools down it contracts and you think something is wrong because you're missing some water.

If you don't keep filling it up each day it should still have some water in it after a few days. If it's overheating you should also be losing power when it's hot.

Well I'll put it all back together today and see what happens. I do usually overfill it to make sure it's got enough water, but I still don't think that's the problem as it does seen to be boiling. I'll give it a thorough look. I have put the lid on when the water is at the full line and same thing happens, but I will re try everything now and try figure it out. Very confusing but I will slowly figure out what's wrong