Club 80-90 Forums

Didn't want my first post to be a problem!

I know this subject is old news.. But it's driving me up the wall now!
I've read everything and tried every method.. I mean every! I can't believe that I'm actually unable to bleed a cooling system!!

So I've got the van to the point of hot coolant with no air from rad bleed valve and thermostat housing valve, all pipes hot, and the fan kicking in etc..

As soon as I take it for a test drive the temp drops initially as to be expected as some air flows through rad.. Then it creeps up and up..
Come to a stop, still coolant and no air from rad valve.. But return hose from rad to thermostat is cold
I'm not joking when I say I must of bled it 6/7 times on the drive and it sits happy with revs held at 3k.. Fan cycling etc.

It's puzzling the hell out of me.

Anyone?

Ok, well firstly let’s clear something up , which may just be how I read it , but still......
the temp gauge doesn’t take its temp from the rad , it takes the temp from the temp sender in the thermostat housing . The switch in the rad is only to switch the rad fan on .

ok, so the air lock you correctly say is passing the temp sender for the gauge is in the thermostat housing , the one facing the front of the van ( the other is the "temp2" switch for the fuel mixture part of the ECU ) 

opening the bleed on the top of the thermostat housing should let that out 

Sorry I should of said, I've got an additional temp gauge.. The sender is plumbed into the bypass hose that runs at the front of engine (as looking from the back of van).

Just seems like I've got it sorted everytime then I go for a drive and I get air in the same hose.

Which temp gauge are you taking the actual diagnosis from ? 
is it really getting as hot as you think it is ? 

Going off the 2nd gauge.. Whilst I'm going through the process of opening and letting air out the bleed valves it sits around 90/95 fine.

I suppose its when I close everything off and either go for a test drive or let it idle with everything shut it starts rising (100+) and then like I say the return hose gets air locked.

It's so frustrating.. The van ran spot on before I decided to do a coolant flush.
Had a recent waterpump and thermostat so I should of left it alone!!

How did you flush it ? 
is it possible you have the rad hoses on wrong way round ? 

and have you got the heater set to hot ?

Another day.. Another go at it!

I flushed it by removing both the main hoses from the thermostat housing as per the Haynes.

Yeh heaters on full and blowing hot air.

It's like airs getting in.. I know this isn't possible lol but it's baffling me. I could understand if I was getting a few air bubbles still at either valve.. Id just keep going at it. But it shouldn't be this difficult.. That's why I posted, wondered if anyone had heard of that particular hose airlocking.

Supposed to be an easy job

After running into trouble over time re bleeding my WBX I just fill it as much as it will take then after the usual in my case hopeless going through the motions bleeding wise, I raise the front a bit, open up the radiator bleed and hang a large water tank up near the rear door hinge (higher than then radiator bleed) then go do something else for a while - the tank being plumbed to the Dalec cap. It works every time for me. So:
What is the needle in the dash nacelle doing?

1. Does it actually boil over?
   
2. Is it losing coolant?
   
3. When you say return hose from radiator to thermostat is cold what stone cold? or just a bit cooler than the feed? Does it feel like it is full of water?
   
4. Is the extra temp gauge properly calibrated? I can’t envisage where you have fitted it.
   
5. Is coolant drawn back expansion tank coolant after journey?
   

 
Apart from a high reading aftermarket temperature gauge and a suspiciously cool pipe have I missed anything else to provide clues?

So.. Yeh it's actually getting really hot. It boiled over once a few days ago whilst attempting to bleed. Aftermarket gauge at that point read around 115.

I'll post a picture tomorrow where the sender is.
It's always sat around 90 so I assume it's about right.

Needle in dash has never since owning van gone higher than about 1/3.. Still hasn't actually, even when it's obviously overheating.

Return hose is stone cold! Like I say.. I can get it hot when bleeding.. Then when the system is closed the same problem occurs.
Everytime.

Yeh the coolant is getting drawn back when it cools down.

Wish I was near some one who could come and show me how easy it's supposed to be!!

I might try your method.. I've tried ever other lol.

We don’t actually know where you are , you haven’t filled in your profile! 

point of note , 115°c isn’t that hot , it wouldn’t boil at that temp if the pressure cap was on and working . 
thermostat doesn’t open until 87°c ( depending on which thermostat you have fitted 

the factory temp gauge is a wide range gauge , the hand book says normal is from just above 1/4 to just under 3/4 

 

Proper instructions for bleeding are here...... there is no need to elevate the van

http://www.brick-yard.co.uk/forum/bleeding-the-cooling-system_topic29710.html

Some further pointers / questions

Why did you decide to bleed the cooling system ?
Have you changed between pink and blue coolant ?
Are you sure that your additional sender is not letting air in.
Where did you buy the waterpump / thermostat from.... in other words what quality

From your description, I'm thinking what you are seeing is a physical blockage in the return, which is why I asked about the coolant type.

Trust the VW gauge

25 minutes on idle should get the coolant warm enough to move the gauge up and trigger the cooling fan, quicker if you force a fast idle

if return hose is cold then thermostat isn't open surely, so if you remove thermostat what happens ?
I've also seen where a reinforcement insert in the front to back pipe had broken up and was acting as a blockage to flow, that was on a return pipe it had come off and moved a couple of inches up the rubber hose, so I'd be checking the state of the pipes and checking for debris if the t'stat out trial didn't resolve it

If a PO has used "barrs leaks" its a great one for clogging the small hoses going up to the bleed rail. I once had this problem, it was the one off the top of the stat cover ans was solid for its entire length. The drilling under the screw was also blocked. Worth checking/replacing.