Club 80-90 Forums

a cooling system in good order takes very little time / effort to bleed if it dosent either you have a system problem or you do not understand the procedure correctly;

from cold

scew the tank cap on the bottle and try and suck / blow through the small pipe outlet .


you should NOT be able to pass air either way

this cap / valve needs a good seal because as the temp rises the water/ air expands , you undo the radiator bleed valve about 1/2 - 1 turn and the air is pushed out due to expansion.

close the bleed screw and repeat a few times .

switch the engine off and undo the expansion cap and top up the water.

if you undo the radiator bleed screw until no air / water comes out then there is no pressure on the system and its safe to undo the cap

DONOT presume the pipes are all unblocked just because they are getting warm , every pipe linking the engine to the bleed ring around the engine bay need to be clear , as well as the link pipes and engine take offs , they can all block up . you will need to physically check them all by blowing through them

ScienceBoy wrote: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.

I'm confused now...

The first tank - the one with the dalek - that's full all the time?
The second tank - the one that you top up through the catflap - that's going up in level?

The dalek should be one-way, from top-up tank to always-full tank. As the coolant heats up and the system pressurises, it shouldn't go the other way.

the non pressure tank , one behind the flap will get warm in normal use

the darlek cap may blow out at a given pressure(water needs to expand with heat and no room in pressure bottle as its full
but will also suck in water whenthe system cools ( water contracts)

the non pressure tank , one behind the flap will get warm in normal use

the darlek cap may blow out at a given pressure(water needs to expand with heat and no room in pressure bottle as its full
but will also suck in water whenthe system cools ( water contracts)

billy739 wrote: DONOT presume the pipes are all unblocked just because they are getting warm , every pipe linking the engine to the bleed ring around the engine bay need to be clear , as well as the link pipes and engine take offs , they can all block up . you will need to physically check them all by blowing through them

Good advice.

I have mentioned this a few times on here over the years. I have seen it with my own eyes on 2 vans and read about it on another 2 on here. A common source of a blockage are any of the very thin pipes that "T" off the bleed rail, and of course the bleed rail itself. I had one van where the "T" connection at the rear left side of the bleed rail was totally bunged up. It caused a lack of coolant flow around the left hand head. This in turn caused the water in that head to boil, this produces steam and pressure that can (and did in my case) cause excess coolant to be ejected.

I'm confused now...

The first tank - the one with the dalek - that's full all the time?
The second tank - the one that you top up through the catflap - that's going up in level?

The dalek should be one-way, from top-up tank to always-full tank. As the coolant heats up and the system pressurises, it shouldn't go the other way.

Too right you are confused....
The darlek cap allows coolant out of the header tank to the top up tank when the coolant is hot and up to pressure at normal engine running temp , and allows the coolant BACK as the engine cools and the coolant returns to ambient causing a vacuum to sick the expanded coolant back to the header tank.

The darlek cap is one way only when cold and under no pressure , same as a normal rad cap

Mocki wrote:Too right you are confused...

It won't be the first time, it won't be the last...

The darlek cap allows coolant out of the header tank to the top up tank when the coolant is hot and up to pressure at normal engine running temp

Umm, so how does any pressure build up in the cooling system, given that the top-up tank is unpressurised?

That's why there are two valves in the cap - one to allow the pressure to build up as the boiling point is increased with pressure (water boils quicker at the top of a mountain as the pressure is lower) so is needed and the other to allow the coolant to return.

Hence why the top up tank rises as water gets hotter and starts to boil.
I know why and how, but I don't know why.
Sticky t-stat
Bunged up pipes
Will need to check if my fan is two speed...

So the fan is a 2 speed by shorting, but I've never heard the top speed come on. But the plug is wired with the common at the bottom rather than the middle terminal as per the wiki.

on a good system running correctly you may never have the fan switch on .

I have done 52000 miles in my camper and the fan has only come on once - in Italy. peak summer fullyloaded with 4 people & towing the trailor up a steep /long hill and that was only near the top!

Ok. I'm looking to replace dalek, thermostat and thermostat top housing, check that common rail around the engine bay is clear, flush and refill. Or I can pay someone to do it...

What size are the bolts fixing the tstat top housing? Two of mine are rusted and rounded.

ScienceBoy wrote:What size are the bolts fixing the tstat top housing? Two of mine are rusted and rounded.

IIRC 10mm head, so M6

Cheers. Any idea on length?

Ok. So they are M6 and about 16mm. So I've got some ss ones in, but of course the bolts at the back are rusted and rounded...
Any suggestions?