Cooling issues

[ninja.turtle007]

After a little advice please. We are currently up at Robin Hoods Bay.


Petrol westy that has been converted to Tdi 25k miles ago. Early water tank with metal pressure cap. The over flow hose is present but no top up tank. The tank has also been about 3/4's full and never requires topping up.

Coolant temp has always sat bang on 92c unless a very long motorway in the Alps area. Then it may go up a degree or two but then settle back to 92C.

Earlier this week, just before we left I changed the heater control valve as the heater has alway blown slightly warn when it should be blowing cold. At th same time I gave it a coolant change. I dumped the coolant and gave it a wash through with the hose pipe. I ran out of time and filled and bled the coolant the next evening.

On the motorway here the temperature fluctuated between 92C and 95C. After 200 miles the coolant level light came on. The end of the hose from the water tank was wet. So it appears to be losing coolant when above 92C.

I have bled the system again.

On the way over the York Moors the temperature fluctuated 89Cto 95C and again the end of hose was wet.

I'm thinking that the thermostat is sticking. Any advice very much appreciated.

I have a new expansion tank and blue cap with me as a spare.

Internet connection is not the best so I will check back when possible.

[AdrianC]

I'm thinking that the thermostat is sticking. Any advice very much appreciated.

Very unlikely. It's much more likely to be the fan not kicking in.

[ninja.turtle007]

The only time the fan has run was when we drove the Grimsal Pass over the Alps.

I have just fitted a new switch from BW and I have the old one as a spare that I know works on the two stages (tested). The fan runs two stages if I short the plug. I know that's not to say that the new switch is working. I'm not saying you are wrong but the fan wouldn't run at 65mph on the motorway, would it? And the temp has always sat at 92c (digital temp gauge) and never dropped off when going downhill like it is now.

My thought was the thermostat is working to an extent but not opening or closing fully.

E D I T: just been told by the wife that she could hear the fan running yesterday when we were going up hill.

[marlinowner]

Could be the cap on the expansion bottle leaking when pressurised, might be worth replacing the bottle and cap.

[Aidan]

run the heater up to temp and see if fluid level goes down then top up, airlock if not bled up with heater circuit on ?

[ninja.turtle007]

run the heater up to temp and see if fluid level goes down then top up, airlock if not bled up with heater circuit on ?

Thanks.

Heater circuit open when bleeding and blowing hot air.

[lloydy]

Could it not just be the metal cap thats failed/failing. You can still buy them. If stuck you could just clamp the little overflow pipe so it doesn't lose the water?
To be fair though i'm amazed you've got sway with that set up for so long

[syncronized]

How much anti-freeze did you add to the water? Over 40% and the cooling properties are reduced so your engine will run hotter

[ninja.turtle007]

To be fair though i'm amazed you've got sway with that set up for so long

??? Not using a top up tank? My understanding was that it would work in the same way as on the golf.

I can now see that if it does loose coolant from increased temp/pressure when it cools there is nothing to replace it.

I can see that a failing cap would allow it to loose coolant. For my information, would it cause the temperature fluctuations that I'm getting?

[ninja.turtle007]

How much anti-freeze did you add to the water? Over 40% and the cooling properties are reduced so your engine will run hotter

The intifreeze is about 40%.

[lloydy]

as far as i am aware the overflow from the goldfish bowl type tank on the golfs discharge back into the system (the large flange on the head has a small spigot for it? like this
http://www.ebay.co.uk/itm/COOLANT-FLANG ... 5b02a587a4" onclick="window.open(this.href);return false;
As for if the failed cap can cause temp fluctuations.. if water can get out, air has to be able to get in. Thats then circulating around the system and causing airlocks?
easy test you could do is refill and bleed then block off that over flow pipe, if all is then good, its the cap. Obviously, if its something more sinister like a head gasket then you may risk popping off a coolant hose.
Not saying thats the right way of testing, but thats what i would do to rule out the cap (if i didn't have a spare)

[ninja.turtle007]

I've now swapped the tank and cap for new style with blue cap as I had them as spares. Fingers crossed.

[lloydy]

Good luck

[ninja.turtle007]

After about a 10 mile run the temp fluctuated between 88C and 95C. 95c up hill and dropping to 88/89C downhill. Roughly 91C on the flat. But no apparent coolant lose.

Before the coolant change the temp would always be 92c and never decrease going down hill and only on extreme hills would it rise a couple of degrees.

I'm still concerned that something isn't right.

[max and caddy]

How much anti-freeze did you add to the water? Over 40% and the cooling properties are reduced so your engine will run hotter

Vw recommend 50% mix....over 65% is where it gets a bit strong.