Just replaced my thermostat and coolant in my 2,0l. Octavia, and the brand new thermostat doesn't open up. I drained all possible coolant by opening a valve at the bottom of the radiator, right side (facing in front of the car).

 

Then took it for a test drive and it went way above 90°c, then I opened up the hood and found out that the radiator fan wasn't turning and the hose from the thermostat to the radiator was not as hot as the the other one.

 

Question is... do I have to bleed the coolant system? If so, is there another valve to open up to let the air/steam out?

DId you flush the radiator and block when you'd drained the coolant? I would have, even if I didn't suspect blocked radiator or hoses.

 

Also, have you tested the new thermostat? It's not totally unknown for them to be FUBAR.

Hi, no I didn't flush either one, just topped it off from the bottom of the radiator.

 

I think that it may have airlock somewhere in the system? Not sure though how to get it out?

Have you installed the thermostat the correct way round?

Correct way? I installed it the same way I took the other one out, is there a way to mess it up?

did you do a fast idle with the cap off? around 3000rpm should shift most of the air - set heating controls set to hot to ensure no block there

 

make sure you have coolant so you can top up

 

then put cap on and pressurise the system - take it a short drive and then check levels again

Ahhhhhh nope didn't have the cap open, I'll try it and let you know!

Edited 5 August, 201510 yr by MaggiSig

Correct way? I installed it the same way I took the other one out, is there a way to mess it up?

 

Have a look at this.

http://www.howacarworks.com/cooling-systems/how-to-replace-a-car-thermostat

The system had an airlock, I removed the cap, let it idle at 2000-3000 for a few minutes and the thermostat opened up, then closed the cap and everything works now.

glad it worked!

Well, it turns out that the car still has some heating problems:

 

1. I let the car idle at 3000 rpm with the heater on full for about 10 minutes with the radiator cap off.

2. I noticed that the thermostat was open, fans were working and the hose from the thermostat was hot (everything looked ok)

3. Then took it for a 20 min. test drive, the heater gauge in the dash was steady at 90°c for about 10 minutes...

4. Then I stopped at a red light and the heater gauge went up to 115-120°c after few minutes

5. I pulled over, opened the hood and noticed that the thermostat was closed, radiator hose from the thermostat was not as hot as it should be.

6. Really don't know what to do..?

try idling it again - squash the heater hoses to "burp" them of air

 

make sure the car does 2 or 3 cycles of the cooling fans cutting in

 

then take for a drive again - if it still does not work suspect the coolant temperature sensor - at 120C the header tank will be boiling!

 

 

then take for a drive again - if it still does not work suspect the coolant temperature sensor - at 120C the header tank will be boiling!

 

Not if the cap is on it won't.

Thanks guys!

 

I'll try it one more time.

 

I replaced the temperature sensor this February so I'm pretty sure it's not it. I had some steam coming from the header tank just when I arrived at my garage when the gauge was showing about 115-120°c

Not if the cap is on it won't.

Mibbae aye, mibbae nay. What's the working pressure if the engine's in good condition?

Mibbae aye, mibbae nay. What's the working pressure if the engine's in good condition?

 

If the coolant system is sealed the cap is either a 1 bar or 1.2 bar cap (cant remember which) so the boiling point of the coolant is 125 degrees plus.

If the coolant system is sealed the cap is either a 1 bar or 1.2 bar cap (cant remember which) so the boiling point of the coolant is 125 degrees plus.

Cheers.

 

The water tables I'm using say 120C at 1bar, 124C at 1.2. So it's a bit marginal for pure water, and I don't have tables for water/OAT mixes, at which point we'd need to know what percentage OAT the OP is running anyway, although I'd guess a Norwegian would run 50/50. Actually, after having been in the Great Glen at -20C a few Winters back with neat screenwash frozen on my headlights (dip on) I run 50/50 myself!