Club 80-90 Forums

Yea to hot to touch, the temperature dial in the cab was at 3/4!

I'll let you know what the garage says

Unless you have any ideas?

If the rad was proper real hot, the rad switch is at fault, to the fan itself.
You need to check the fan and switch, by "shorting" the switch out, if the fan comes on it's the switch, if the fan don't come one it's the fan or the wiring

However , you need to get round this bleeding up thing....
Run van up to temp with the header tank cap off, increase revs to 2000 rpm, keep revs at 2000 rpm and open the rad bleed screw 4 turns , either air or coolant will come out .
One or the other.....

I have EXACTLY the same problem. Fine when driving, overheats when parked when fan doesn't come on. Heat comes out of heater so hot water is coming to the front via thermostat. Note that the cab reading comes from the engine, but the fan is triggered by a switch in the radiator, so completely different places.

So I'm off outside to try some bleeding (I also did some coolant fixes and concerned I introduced air to the rad - and air expands 22 more times than water if I recall my fluid mechanics lectures correctly)

ScienceBoy wrote:overheats when parked when fan doesn't come on.

Umm, have you considered fixing the fan?

ScienceBoy wrote: overheats when parked when fan doesn't come on. Heat comes out of heater so hot water is coming to the front via thermostat.

Most vehicles have the cab heating coming from the engine before the thermostat otherwise a lot of the time you will have finished your journey before you got any heat up front!
Suggests non-opening thermostat not a correctly operating one.

Oldiebut goodie wrote:Suggests non-opening thermostat not a correctly operating one.

Nah, it'd overheat whilst moving, too. Which we're told it explicitly doesn't.

As i said, almost exactly the same. Read Haynes earlier so sussed heater isn't on same circuit.
Fan doesn't come on doesn't mean fan doesn't work. Shorting it shows the fans ok.

So went to bleed it. Thermostat is fine and hot water does go to the radiator. Always a good idea to check the angles before ripping out components...

Followed the bleeding process front and back. Added more water yadda yadda.
Why is the radiator bleed so long and awkward. Must get ratchet spanners. Why isn't a bleed akin to domestic rads?
Anyhoo, that all worked fine. Ran at revs, rad warm up, water spurts out, air is expelled, and fan comes on.
Yippee

Looks like my issue was a airlock in the rad not letting the fan switch see the high temp water. I'll find out more with a good run this weekend.

But the heat is still not reaching the front via the thermostat as was stated (it doesn't normally go through the thermostat to the cab heater) - which was the point I was making. Non fully opening thermostat would give the symptoms.

Given the fact it boiled over again this weekend I'm thinking sticky thermostat. Probably got 20 years of limescale.

Can you have a temperamental water pump giving these symptoms?

ScienceBoy wrote:Given the fact it boiled over again this weekend I'm thinking sticky thermostat. Probably got 20 years of limescale.

Can you have a temperamental water pump giving these symptoms?

Let's go back a step here...

You start the van up, from cold. It starts to warm up.
How quickly does the needle start to move?
How high does the needle move before the heaters starts to blow warm?
How high does the needle move before the radiator starts to get warm?
Does the radiator get warm evenly?
When you're on a long run, does the needle sit in roughly the same position at all times?
When the needle starts to rise beyond the "usual" position, does the fan kick in?

we had the same issue on my mates van, it was a combination of two things in the end.

gsf stats are pants FACT!!

and his rad was partially blocked, it would get super hot but spew water out till we swapped the new stat for a brickwerks one.

jason k wrote:
gsf stats are pants FACT!!

+1

OK. Started the engine from cold. Haven't actually started it since Christmas.
+2m50 water pump coolant pipe starts to warm
+2m30 needle starts to move from rest
+3m12 water pump coolant pipe is getting hot
+1m35 cab heater starts blowing hot air
+3m50 needle is making it's way through the white section and towards 11o'clock on the gauge and the radiator starts to warm (so the thermostat worked this time)
+8m10 radiator is hot, needle is hovering around 12 o'clock and the fan kicks in.

However the fan doesn't stay in for a long time, and the needle still hovers around noon. The water level in the reservoir is rising, but stays an inch shy of the vent. The fan kicks in a few time over the next few minutes, but everything else stays might like above.

I then rev the engine to take it off "choke" high revs. The odd thing is that after a while of being stable, the water level in the top-up tank rises and starts dripping out of the vent. I switch off. Could it be the higher revs are allowing the water pump to push more water to the radiator and keeping things stable? Reducing the revs lowers the coolant flowrate which allows an overheat?

I recall that previously the temp used to stay around 11 o'clock on long journeys. I'm thinking that not kicking in until 12 o'clock is sailing close to the wind. Anyone know at what point on the gauge their fans kick in? I know that the temp sender is back in the engine bay and the fan actuator is on the radiator.

I also used a narrow pipe to listen to the operation. Water pump sounded OK under the noise of the rest of the engine. I could hear water gurgling through the radiator once it started to warm.

Woah - hold on one minute...? The water level in the EXPANSION tank starts to rise? The tank inside the catflap? (The main tank should be full to the brim to start with)

If so, then your dalek's dead. Everything else sounds pretty much perfect. Exact positions on the gauge are irrelevant - there's no absolute calibration. If you want to be certain, get an IR thermometer, and check the temp of the rad fins when the fan kicks in and out.

The water in the expansion tank is fairly static, but it has nowhere to go until it pops the dalek. I was referring to the level in the header tank. As this is open to the atmosphere, any expansion in the coolant system pushes tank to where it can go without back pressure; that'd be the header tank.

As water doesn't expand much, I had previously reckoned an air trap. But I've vented fore and aft. The radiator get uniformly hot. Unless the vent on the t-stat housing isn't venting, where else might have air?