Temperature gauge rising!

Juat had a worrying moment - got back from short run, only about 6 miles or so round trip (well hot here at the mo though, 30 something in the shade) and as parking at home noticed temp gauge 2 thirds up the scale. never goes past half way usually.
Eased expansion cap off, not very pressurised and full of coolant. Oil, dipstick looks ok and coolant looks ok, no visible mayo or contamination.

Noticed top hose to thermostat housing is hot but feels empty. Any (very very urgent) top tips to investigate please?
Cheers
Rich

sp33der said:

Juat had a worrying moment - got back from short run, only about 6 miles or so round trip (well hot here at the mo though, 30 something in the shade) and as parking at home noticed temp gauge 2 thirds up the scale. never goes past half way usually.
Eased expansion cap off, not very pressurised and full of coolant. Oil, dipstick looks ok and coolant looks ok, no visible mayo or contamination.

Noticed top hose to thermostat housing is hot but feels empty. Any (very very urgent) top tips to investigate please?
Cheers
Rich

Click to expand...

I would remove the plastic bung in the top of the thermostat housing when the engines cold and check to see if it is full of coolant, it should be.

Hmm, plastic bung has been 'upgraded'! Had to do a repeat run an hr or so ago, only an hr or so after the 'overheating' run. Same journey there and back, left the aircon off to save loading the engine and needle stayed exactly half way.

Big hose to thermostat housing still has no coolant in it though - I checked it as soon as I got back. Airlock? Faulty thermostat? I would have thought that if it was low on coolant, the expansion tank would empty but immediately after the first run it was quite full and went down to normal over the next hour or so before my second journey.

sp33der said:

Hmm, plastic bung has been 'upgraded'! Had to do a repeat run an hr or so ago, only an hr or so after the 'overheating' run. Same journey there and back, left the aircon off to save loading the engine and needle stayed exactly half way.

Big hose to thermostat housing still has no coolant in it though - I checked it as soon as I got back. Airlock? Faulty thermostat? I would have thought that if it was low on coolant, the expansion tank would empty but immediately after the first run it was quite full and went down to normal over the next hour or so before my second journey.

Click to expand...

You have to fill the coolant thro the thermostat housing, you can't fill it thro the expansion bottle, it doesn't work.
Could be a problem with the thermostat, worth changing for what they cost.
Just make sure you put in in the right way up, jiggle pin to the top otherwise the top hose doesn't fill with coolant.
Top the system up and let the engine idle with the thermostat bung out until the air clears.
There is a possibility your radiator is furred up and needs replaced unfortunately.

That sounds like an air pocket. When the car is hot, the air expands more than the fluid does and is pushing the fluid back into the expansion tank, which would explain the quite full after the first run. Once it cooled, it sucked back into the system. These systems need correct filling to prevent airlocks. My Land Rover expert in Zimbabwe aho looked after my 300 Tdi had a technique to get all the air out. Remove both bungs (top of rad and thermostat housing), fill with coolant through expansion tank till slightly overfull. Then put your mouth on top of expansion tank opening and blow - any trapped air should bubble out of the other two openings. When just coolant flows, get an assistant to fit the bungs. Then adjust coolant level in expansion tank.

Hopeully it's that and not head gasket. I had overheating problems for a while and mine was the water pump, which wasn't too expensive.

Good Luck
Graham.

Hi Rich, thats sounds to me like a sticky stat and its not opening all the way....But then again due to your extreme temps it may be down to natural evapouration within the cooling system.Try topping the system up first through the housing bleed cap before you consider changing the stat.

Dave
A Geordie in Durham

Thanks a lot Niceday, Graham and Dave. I may just bung a new stat in tomorrow anyway as it's cheap and easy (well it should be).

Topped up system as best I could - couldn't get plastic bung out of the radiator end but disconnected hose and topped rad from it. Topped up at thermostat housing and replaced thermostat.

Still temp gauge does this occasional rise - up to about 2 thirds then down again to half way. Had to do airport run last night and after about 50 miles of motorway with aircon on it scared me by doing it again. I turned off the aircon and it settled back to half way almost immediately. Return trip fine (didn't use aircon though, didn't want to break down with mum-in-law, sis-in-law and baby on board at past midnight! :crazy_driver: )

Does this sound like a rad problem? I'm thinking/hoping a flush might help. Whilst doing all this I found out why my heater doesn't work - I had thought this might tie in with the air-lock theory but it's because the matrix has been bypassed so presumabley it's fooked! Now's there's another whole kettle of fish to be sorted at a later date!

300tdi's are buggers to get all the air pockets out, Try putting the front end up on ramps then unscrewing the 'stat plug and filliing the system from there with a hose pipe - you will get wet but it worked for me.

sp33der said:

Hmm, plastic bung has been 'upgraded'! Had to do a repeat run an hr or so ago, only an hr or so after the 'overheating' run. Same journey there and back, left the aircon off to save loading the engine and needle stayed exactly half way.

Big hose to thermostat housing still has no coolant in it though - I checked it as soon as I got back. Airlock? Faulty thermostat? I would have thought that if it was low on coolant, the expansion tank would empty but immediately after the first run it was quite full and went down to normal over the next hour or so before my second journey.

Click to expand...

Hi mate, make sure you fill up the coolant via the thermostat housing plug, then run the engine with the heater controls set on hot - yeah I know but it pens up the heater matrix to try and ensure no airlocks. Once you are confident that the coolant is full, go for a run.

At the age of all TDi's the rads are likely to be a bit cacked up so could need replacement but also check the functioning of the viscous fan.

With the aircon on, you should have the condensor fan running as well which should aid engine cooling, rather than overheating it?

Cheers
Dave

" then run the engine with the heater controls set on hot - yeah I know but it pens up the heater matrix to try and ensure no airlocks"

Come on now Dave mate, pay attention - last bit of my message three posts back, when I relate the fact that I've just discovered that the matrix has been bypassed which is why I have no heater!

I'm sensing a rad problem although after your post I'm wondering if the condensor fan could be faulty...........no, I think the gauge rose a little last night, just briefly as ever, on way home with no aircon on.

Cheers for all input lads

Rich

sp33der said:

" then run the engine with the heater controls set on hot - yeah I know but it pens up the heater matrix to try and ensure no airlocks"

Come on now Dave mate, pay attention - last bit of my message three posts back, when I relate the fact that I've just discovered that the matrix has been bypassed which is why I have no heater!

I'm sensing a rad problem although after your post I'm wondering if the condensor fan could be faulty...........no, I think the gauge rose a little last night, just briefly as ever, on way home with no aircon on.

Cheers for all input lads

Rich

Click to expand...

"Keep yer pants on Rich", remember I'm 58 in a few days, be more respectful of the old gits.

I reckon it's your rad if all else is ok, and it couldn't hurt to do a flush, could it?

Please be gentle with me, I'm 84 your know........................

Dave

During the war son, during the war...

My pants are in place! They may be incontinence pants but they are in place!

I'm def thinking rad, that's the way forward. Mind you, prospect of matrix is daunting, aircon et al, but that's for another day.