Club 80-90 Forums

Right; I was coming home from work and the temp gauge headed North and steam then came out the back. Pulled up and cooled down (me and the van) topped up the header tank and carried on home and the heater was cold, the gauge went way to the right after a bit but got home with still a fair bit of coolant in the system.
First diagnosis was the thermostat so bought a new one and have put it in (after mullering the housing; another tale of mechanical incompetance). Replaced coolant and bled the system according to the excellent advice from Brikwerks. Went for a run and the temperature gauge is good (in the middle) then goes a bit cold then starts moving way to the right-lose coolant. Top up and re-bleed.Then check the thermoswitch on the rad. and find that the fan kicks in ok. Sit in the van and rev it up to gain temp. and it sits steady on the gauge in the middle. Sit there for a bit longer and probably annoying the neighbours so pop up the road out of the way and park up and rev it up some more. Sit there for a bit (15 minutes) and the gauge is in the middle and no fan kicking in. Then the gauge creeps past the mid point and still no fan; the gauge goes right; no fan, but top of radiator hot and heater toasty. Guage then gets very excited.
Would it be a fair assumption that the thermoswitch is dead?

If its genuinely getting hot and spewing out coolant then either the pressure cap is faulty, the rad is partially blocked or there is a serious problem with the engine...
Sitting with it running will take an age to heat it up.. there is 18L of coolant and a lot of surface area to loose the small amount of heat going into the system.. a light breeze through the rad will take away plenty of that heat..

Soon as you start driving, it puts a lot more heat in..

Do the coolant hoses seem very hard when its up to temp?
Does the lower part of the rad feel hot when its getting hot??

Has anyone stuck any rad weld in it?? as they really really dont like it.. the only product that seams to have been used successfully is K-Seal

rad should be hot from the bottom first.. slightly cooler at the top...
you can get lower temp thermoswitches.. whatever you get..get it from brickwerks.

kevtherev wrote:rad should be hot from the bottom first.. slightly cooler at the top...
you can get lower temp thermoswitches.. whatever you get..get it from brickwerks.

If the engines v hot and any part of the rad is cool/cold... there is a flow problem..

toomanytoys wrote:If its genuinely getting hot and spewing out coolant then either the pressure cap is faulty, the rad is partially blocked or there is a serious problem with the engine...
Sitting with it running will take an age to heat it up.. there is 18L of coolant and a lot of surface area to loose the small amount of heat going into the system.. a light breeze through the rad will take away plenty of that heat..

Soon as you start driving, it puts a lot more heat in..

Do the coolant hoses seem very hard when its up to temp?
Does the lower part of the rad feel hot when its getting hot??

Has anyone stuck any rad weld in it?? as they really really dont like it.. the only product that seams to have been used successfully is K-Seal

Yes, the coolant hoses seem very hard when it's up to temp.
Will check if the lower part of the rad feels hot when it's getting hot. What would that indicate; that the rad is pretty clean?
No idea about the radweld; why don't they like it (they don't like it up 'em Pikey)?

I really don't think it's a head gasket problem (although I may be in denial) as I've had one go on a Pinto engine and it was pretty immediate and scolded my ankles; it was my own Westfield.

Very hard hoses means a lot of pressure.. either an air lock if its not bled properly not flowing the water, either coz the pump isnt.. or the rad blocked, or T'stat (which you've changed)....
Head gasket is feasable.. as I said 18L of coolant is a lot.. Pinto in a westfield is what? 5L tops....

The old wbx is pretty forgiving to abuse really.. thats why when the give out, its usually pretty terminal...

Worth looking on the heads.. see if the large domed nuts are all still there (4 visible on each head.. 4 inside the rocker covers)

Check your oil level too.. as if one of the nuts in the rockers has come adrift (studs rot and the nut falls off) then the sump could have water in it...
Heads crack occasionally too... and thats only poss to see upon dissmantle..

Might be worth asking your locak garage to do a "sniff test" (actually a chemical check rather than sniffing with his nose) on the coolant for combustion gasses..

Yes I agree that if the radiator is getting hot and the gauge reading 2/3rds then the first speed on the fan should be kicking in.
I replaced my thermo switch last year and generally the only time it does kick in is whilst idling and in stationary traffic for several minutes (this is because although the engine is not being worked hard there is practically no airflow through the radiator taking away the heat from the fins)

I used one of Brickwerks... Wahl units (£13..something) which are an original parts manufacturer for VW. Two speed thermo fan switch (unless an early CS engine) one in one out (remove lower grill to access) you only loose a small amount of coolant...just bleed from the top bleed screw on the radiator and top up the coolant.


Martin

Dont forget that the gauge reads from the engine, not the rad.... if the rad isnt getting hot top and bottom because of low flow, then the switch will never work and the fan wont come on... check the rad first, and if it is hot then the switch is prob faulty..
How did you check the thermo switch??

Just going slightly off subject but when I used to work at Nottingham Volkswagen (Bristol Street Motors) we would fit these switches by the bucket load....well maybe a slight exageration but certainly we fitted alot of these to all the VW range of that era...mid eighties.
I suppose this is just a note really as replacing these doesn't seem to be 'first port of call' anymore......with all the other possible culprits I guess it's easy to overlook the obvious.
So
My advice would be to check how hot the bottom of the radiator is getting and if it is very hot then the thermo switch is probably a good bet.

Martin

toomanytoys wrote:Dont forget that the gauge reads from the engine, not the rad.... if the rad isnt getting hot top and bottom because of low flow, then the switch will never work and the fan wont come on... check the rad first, and if it is hot then the switch is prob faulty..
How did you check the thermo switch??

Thanks so far.
Shorted the wires to the fan and it worked. Then removed thermoswitch, put it in boiling water and got open circuit across any combination of terminals.

firstly its a early cooling system, so the gauge will be 8litres either ahead or behind the real temp, and 17litres infront of the rad switch. Did you change the temp switch in the thermo housing when you changed the thermo housing?

i would say this time of year the rad fan shouldnt ever come on unless you are thrashing it then standing it on tickover immediately. I wouldnt worry about the rad switch, it isnt your cause, although it maybe a seperate issue.

i would say its either still got air in it ( early cooling system MUST be raised at the front despite what others say - there is no bleed ring)

the cause of the air , well, if you are luck, hairline crack in header tank, cap or pipe and not a cracked head.
water jacket seals never cause high pressure in my experience.

worse case its getting combustion gases in the coolant.

Not looking good. I've put a new thermoswitch on and bled the system. Still getting overheating. I noticed that with the engine running, on a good slope with the nose in the air and the cap on the expansion tank then bubbles are coming out of the top pipe into the expansion tank. Is this still possibly air in the system that needs bleeding or (and I know it could be) more likely combustion gasses.

id get that sniff test done ian,before spending any more money..if it comes back ok then look at the rest of the system and itll be peace of mind too

Assuming you have an empty system, open the header tank, and fill up, put you hand over the top of the tank, and squeeze the rad pipes, moving the water around and letting the air out, keep doing this until no more water will go in, then.......
Put the van up your car ramps, or jack the front up at least 12"(or park on a hill!!)You cannot bleed a early petrol T25 any other way, the shape of the cooling pipes makes it a scientific impossibility!
Put the heater on HOT, and undo the filler cap on the expansion tank, Run the van upto temp, so the thermo stat opens,
then increase the revs to 2000 rpm, then top up the expansion tank, and undo the bleed screw in the radiator, and then the one in the engine bay(if it will, do NOT force it) Keep topping the expansion tank up, ignore the top up bottle(behind the number plate) and keep topping up until only water comes out of the radiator bleed screw, should take about 20 mins, then put the top on the expansion tank, close the rad bleed screw, but leave the engine bay bleed screw open(if you opened it) then reduce the revs to tickover, leave for about 2 mins then switch the engine off, go have a coffee for about 20 mins, then come back, start it up, increase revs to 2000 rpm, open bleed valve in rad, and if you have a caravelle with rear heater, open the bleed valve in the top of that too(by the in/out pipes)take top off expansion tank and repeat bleeding until no air, only water comes out of the rad bleed screw, when you think it is all done, then put the top on the expansion tank, close the rad bleed screw, the engine bay bleed screw open(if you opened it) then reduce the revs to tickover, leave for about 2 mins then switch the engine off. Job done......

it takes about 15mins longer than you think it should, and you always need to do it one more time than you think you needed to....in short, when you think you have finished, go have a coffee, come back and do it again.

Thanks again.
Am now giving it a reet good bleeding, but have arranged for a sniff test on Tuesday.