HELP please! HOT w/o thermostat?

[Smiley]

The symptoms are somewhat normal - the water temp is too high, the aux rad is hot, although the coolant hose from the thermostat to the radiator bottom stays cold. This (i would think) is 'normal' with a thermostat stuck closed.

A brandnew BEHR thermostat went in, to no change.

I tested the one i removed in cooking water, it opens fine. Somewhere i read to add a small hole in the thermostat to make a small way free for air bubbles. This way the thermostat is guaranteed to be settled in coolant all around. This went in. No change

So i removed all the springs from the thermostat and fitted the 'base ring' only. This way i simulate a thermostat stuck open. No change.

When i look into the hole where the thermostat goes, i see one hole going backwards to the heater.. Is there another going forward or straight inside the block? I cant'
see..


Any comments welcome !!!


I will now go out for a beer to gain some spirit
and start again tomorrow morning..

[A80Avant]

hmm that is i a tricky one...
is it possible that you have air in the system?did you take all the air out after each change of the thermostat?

[Smiley]

I forgot to mention that the heating works.

[Smiley]

I don't think its air in the system. I open the two bleed screws, the one on top of the rad and the one to the heating, and then fill the system up until the coolant comes out (both at the same time btw). As there is no thermostat i would think the coolant would flow all round..

[A80Avant]

yes then it cant be that...

i had a new thermostat put in once and istead of 80C it opened in 95C... so you could have a faulty thermostat as well..

[Jamo]

The symptoms are somewhat normal - the water temp is too high, the aux rad is hot, although the coolant hose from the thermostat to the radiator bottom stays cold. This (i would think) is 'normal' with a thermostat stuck closed.

Eh?

What you've described is correct there. The aux rad gets hot coolant from the top of the rad so the top hose will be really hot!

The hose that goes from the bottom of the rad to the thermostat should be cold coolant as it has been through the rad!

The thermostat opens when the engine coolant is too hot letting in the cold Coolant from the rad circuit.

Why do you think it's too hot? The temp should go to 90c and then the fan kicks in.

[johne]

With the thermostat removed you should see two passages. One goes straight into the block from behind the thermostat (which is the one the round plate on the back of the thermostat blocks during the warm-up phase) and one to the right that leads from the heater.

Sounds to me that you could have a blockage in the bottom of the main radiator. I'd try reverse flushing the main radiator. If you've got lots of crud in the cooling system, try running with a dishwasher tablet in for a couple of days and then throughly flush the system.

Whilst it's OK to put a hole in the thermostat to check the bleeding theory, don't do that as a long term solution. I bought a new thermostat from GSF, brand Frusser, and it had this hole in it. As a consequence the engine ran cool when cruising on the motorway under light load - useless. Had to replace it

John

[Beetie]

He has read a thread where i recommended it to someone in a warm climate, thus helping the car run slightly cooler. Of course we dont really need the hole in the thermostat in our glorious weather....

[Mikes2]

I had something similar on one of my cars recently. I could only get hot air in the cabin once the car had gone above 2500 rpm and the fan wouldn't come on.

reason for the fan not coming on was because the bottom hose was staying cold.

I fitted a new thermostat and bled the cooling system

I also had to adjust the alternator drive belt.

Once done all was ok again.

I would check that the outlet hose from the heater matrix is getting hot because that's where the water to your thermostat comes from.