Radiator Thermo switch

[Firkie]

I've tried wiki and although loads of heating issues I couldn't find anything which helps me.
Problem is my rad fan has never worked, and because there is a long list of jobs to do I just fitted a switch direct to plug ( Heath Robinson I know) just a temp thing. Now I've got round to the issue I've run engine allowed thermostat to open and close then kept me eye on needle. I allowed gauge to climb to three quarters before switching engine off keeping in mind the thermostat keeps the running temp in my van just slightly over half way. Now I've got a switch on the dash so the fan does work ( not at stage one though?) so it's not the fan...solution must be radiator thermo switch? Brickwerks replacement fitted yesterday! Ran it up and got to three quarters again fan came on but just for five secs temp still rising !! Switched off. Went to back of van and water on the floor!! I feared the worst . But luckily it was coming out of the top of the top up tank ( overflow ). Today I thought I would changed the connectors on the plug so the second stage would kick in at the first stage. Same again!! But today I placed my multi meter on continuity and kept testing the thermo switch as temp was rising...nothing! But gauge at three quarters and water on the floor!! I believe system is bled correctly, water level correct( can't put more in than it can take!) rad is uniformly hot!! I want the system to work as it should and not off a dodgy switch.
Sorry for the life's story but wanted to include all details. Any help much appreciated

[kevtherev]

Firstly, early vans only had one speed fans.
the fan will switch off because the coolant in the rad has cooled enough to switch it off.
If the circulation of coolant is poor due to air in the system, gunged up radiator, or a failing pump then this will happen

I hope you checked the new thermostat opened fully before you fitted it...being new does not prevent a dud being sold to you.

[Firkie]

I haven't had a new thermostat ? I've fitted a new thermo switch on the radiator and the van is dropping water because I think it's getting too hot because fan isn't kicking in, only once and only max five secs , gauge just past three quarters!The van doesn't use water in normal driving conditions and I've always kept my eye on the gauge and if its working hard and the temp starts to rise I flick the fan switch on the dash to cool things down .
The thing I don't understand is the thermostat controls temp by holding water in engine until it reaches certain temp and then opens to release hot and welcome cool, so if my gauge position is just past the middle when thermostat opens surely running at three quarters means the thermostat is permanently open because when the cool water enters engine the gauge drops to half then climbs steady to just past half then drops to half etc etc.
I'll try bleeding again although rad is hot all over. As for blockage, surely I would be running hotter when normal conditions apply??
Anyway thank you for your advice, I'll keep scratching at my growing bald spot and let you know if I get it sorted ??

[kevtherev]

The gauge should not really fluctuate like that.
If you haven't fitted a new thermostat then I would suggest you do.
the thermostat does not open and close.. once temperature has been reached then it stays open.
the blockage could be the old thermostat not opening fully.... thus causing the engine to overheat..and leaving the radiator with nothing to do.

[Firkie]

I'm not 100% but I thought if you get a thermostat that's stuck open you won't get the heat in the cab because the water is not getting heated sufficiently by the engine because it is constantly being cooled?
Like I've said the van runs lovely without the fan in normal conditions flat road and not stuck in traffic it's just when you put it in the situation of no wind cooling the rad

[kevtherev]

I'm not 100% but I thought if you get a thermostat that's stuck open you won't get the heat in the cab because the water is not getting heated sufficiently by the engine because it is constantly being cooled?

Wax stats open fully or close fully
heat in the cab is directly from the engine (No. 1 cyl) it does not pass through the rad.

[Firkie]

Well there is no point in having a stat only to warm the water up quicker initially. You learn something new everyday. I like the diagram, I've saved it for future reference.

[stove]

Hi Firkie,I had similar coolant issues on a JX engined van,going up long hills had to turn cab heater to hot and heater fan on 3 (full) just to keep the temp down.The rad was getting uniformly hot as you discribe and new switch and thermostat fitted,in the end I came to the conclusion it was the rate of flow in the radiator.New rad fitted and needle never gone over half way since.You could try back flushing the coolant system to see if this will dislodge any gunge and improve circulation but it didnt work for me .Best of luck Stove.

[Firkie]

Cheers stove, I'll give that a whirl and hopefully I won't need a new rad! I bet they are pricey? Did your radiator fan kick in when your temp went up?

[stove]

No,never kicked in nomater how hot it got ,shorted switch out just like you have done and it still did not control the temp,the only thing that would bring it down was cab heat on full.Always ment to open old radiator up to see how badly blocked it was .Now it never gets hot enough to come on unless I leave it running on the path for about 20 mins.

[California Dreamin]

OK.....you say it goes upto 3/4 's and then overflows from the topup tank...so are the hoses getting hard (pressurising) before the coolant expands and overflows?

The reason I ask is, the Darlek Cap (pressure cap) should only release excess coolant once the coolant pressure reaches around 1 bar regardless of temperature.
If it is leaking back to the topup tank without pressurizing the system first the cap is clearly faulty.

Martin

[HarryMann]

Rads were about £120

Def worth draining and backflushing, new good make of stat too, test...
but as Stove says, might not work.
'Tis an old van, maybe a 2nd hand rad ?

[California Dreamin]

German EIS radiators cost £72.36 with FREE POST ...USE discount code CP10LESS at the checkout.

http://www.carparts4less.co.uk/car-radiator

Martin

[Firkie]

My van doesn't loose water normally and I've been up and down the hills at buxton a couple of times. But I've always kept my eye on the gauge knocking the chicken switch in and out. I'm I right in saying if there was a problem with something which pressured the system then it would happen at any temperature given time? If this is the case then it must be linked to the temp because its never lost water until I let it stand ticking over to test the rad fan after fitting rad thermo switch . I think stove has solved my problem ?? If the flow is restricted through the rad then the thermo switch isn't picking up the correct coolant temp?? Which would prevent the fan coming on at the correct time and allowing to temp to continue to climb? It makes sense to my thinking, but I'm far from being an expert

[Firkie]

German EIS radiators cost £72.36 with FREE POST ...USE discount code CP10LESS at the checkout.

http://www.carparts4less.co.uk/car-radiator

Martin

Cheers Martin I might just go for it at that price. Looking at my rad it looks pretty decent, but that means nothing to what's going on inside.