300tdi overheating...still

[tomfoxley]

Hi,

Basically, the damned thing keeps on overheating. The problem started when the auxiliary belt popped off and shredded. The water pump broke at the same time. The pump was replaced with new gasket and pulley and belt. I filled up the expansion tank and went for a test cruise. It overheated - only a tiny bit of steam. Luckily I was just doing loops of where I live so I stopped for an hour or so then limped home when it had cooled sufficiently.

Suspecting an airlock, I completely drained the system and flushed it before filling it again slowly through the expansion tank. I couldn't fill it through the bit near the thermostat as the oaf who owned it before me has rounded the plug completely. So slowly it went in...

I gave it a test drive a while ago and what a surprise, it overheated again. I went to the front and had a look around. There was no pressure in the expansion tank and although the top rad hose was very hot it felt like there was nothing in it. Also the hose to the right of this felt empty too ( I don't know what this is because I'm relative novice). I was too ****ed off to look for anything else so I read the new edition of lrm and thought about how much better things would be if I looked at the disco before buying it from eBay.

Any help would be hugely appreciated, thanks.

 

[colinl]

do both pipes from the radiator get hot?
does the heater blow hot air
do the pipes pressurise
is the thermostat ok.

 

[Soloby Rob]

do both pipes from the radiator get hot?
does the heater blow hot air
do the pipes pressurise
is the thermostat ok.

Does my bum look big in this :hysterically_laughi

 

[disco147]

i'd work on gettin the bleed screws out, chuck some brass replacements in, flush the heater matrix if the heaters aint gettin hot inside, fill the system and bleed it via ya nice new brass bleed screws. Replace the thermostat whilst ya doing it - should cost you an afternoon and about 20 quid to do that. Report back when yer done

 

[basher79]

sounds like an air lock

 

[tomfoxley]

do both pipes from the radiator get hot?
does the heater blow hot air
do the pipes pressurise
is the thermostat ok.

Top pipe was hot, couldn't be bothered with going underneath to look at bottom pipe when it was wet and muddy.

Heater doesn't blow hot air.

Top pipe doesn't feel pressurised.

Thermostat should be ok, I only replaced it a few months ago.

 

[thebiglad]

Top pipe was hot, couldn't be bothered with going underneath to look at bottom pipe when it was wet and muddy.

Heater doesn't blow hot air.

Top pipe doesn't feel pressurised.

Thermostat should be ok, I only replaced it a few months ago.

1. Is the coolant in the header tank getting any heat into it? If it's not, go to step 2:

2. My wife's TDi 300 was doing something similar and it turned out to be the 2 into 1 small bore pipe between the thermostat housing,the header tank and the top of the radiator. It's the one with the circular valve in it.

 

[Gordy88]

whip out the thermostsat and try it, they can fail even when newish, had it happen with pattern ones before

Might think about the water pump too, i had a 14 quid ebay special on my 300, lasted about a year and a day!

cheers

 

[tomfoxley]

Thankfully it was just an airlock and with a bit of squeezing of pipes etc it works again. I managed to replace those crap plastic drain plugs with brass ones too. Thanks everyone, much appreciated.

 

[basher79]

good to hear