Overheating, cold bottom hose?

[Eighteeteewhy]

The car in question I a Audi 1.9 tdi. When you drive the car the temp rises and rises. The top hose is hot/pressurised but the bottom hose is stone cold. Thermostat has bern changed but the problem persists. I now have the water pump off and it looks ok?

Any help welcome.


@

[trickywoo]

Do you still have the old thermostat? If so test it in hot water. If it works I'd suspect something like a blocked radiator.

If it doesn't work I'd suspect, however unlikely, that the new one you fitted is also faulty.

[scotty_d]

Sounds like air in the system, give it a good bleed again and report back.

[ADEuk]

Not sure if yours is the same but on some VAG engines the thermostat housing has a small tag that the stat rests against. If this breaks off the stat has nothing to push against in order for it to open.

[HustleRussell]

Too late but I'd suggest 'stat (there is more than one on some engines) or air lock. What does the engine temperature gauge say?

[Eighteeteewhy]

trickywoo said:

Do you still have the old thermostat? If so test it in hot water. If it works I'd suspect something like a blocked radiator.

If it doesn't work I'd suspect, however unlikely, that the new one you fitted is also faulty.

Hi I've got the original stat plus two others, tested them all.


Forgot to say, it's a new rad as well.

[ADEuk]

What happens if you run without a stat (or remove the guts of one if can't assemble without a stat in place)?

[HustleRussell]

It probably needs bleeding. It's an arse of a job on some cars.

[littleredrooster]

Does the heater work? If not, I suspect water pump or air in system which is preventing the pump from circulating the coolant properly.

Next in line of suspicion would be the temperature sender - could it be telling little lies?

[HustleRussell]

Oh and I don't suppose it's possible to install the 'stat the wrong war around in one of those?

[s p a c e m a n]

Im going to go for the you aint bled it properly option

What does it do if you leave the cap off of the header tank?
Can you see water returning, how much does the water level change when you squeeze the hoses and are the heaters blowing hot?

Edited by s p a c e m a n on Wednesday 30th January 15:12

[Robatr0n]

Eighteeteewhy said:

Forgot to say, it's a new rad as well.

As others have said, it'll most likely need bleeding.

With some cars this involves jacking the front end up in the air / getting the car upto temperature with heater on full blast / bleed nipple open / cap off header tank or a mixture of any of these.

Some are a complete bh to do.

[Eighteeteewhy]

Stat cannot be fitted the wrong way

I'm going to change the pump anyway as I've got it off and a new one is cheap.

Not sure where to go after that.

[Sogra]

seem to remember that this has always been a problem on that engine. the problem being that the expansion tank is slighlty lower than the highest cooling channel in the engine where air gets stuck.

fill slowly with hot water and (add antifreeze) with the engine running, if you can park the front of the car (both front wheels) on a kerb so the radiator and expansion tank are higher than the engine that should help. heater fully open.

As the engine heats up squeeze the bottom hose, you should see air bubbles coming up from the expansion tank.

When the bottom hose is hot and the fan kicks in put the rad cap back on.

Out of interest why was the rad changed in the first place as could be associated problem with rest off cooling system?

Sog

[Easternlight]

Try asking in the VAG section there's a couple if guys in there that seem know their stuff

[TROOPER88]

Another one for def air in the system.

Expansion cap off, blowers on hot and full, run for 10 mins or so revving a bit throughout

[Eighteeteewhy]

Cheers for all the suggestions guys, I shall put them all into practice when it goes back together.


I shall report back.