landowner

landowner

Pensioner Pete
Full Member
Defender 90 with Disco 200tdi and Disco radiator/intercooler
Defender header tank
Fairly recent new aluminium radiator
My cooling has never been quite right, the header tank has never ever got even warm, the engine warms up quickly and the heater is toasty, usually the temp stays normal and I used to check the thermostat housing and top hose with a laser and all was ok.
The radiator gets hot at the top corner where the top hose goes in, its warm all over but the bottom hose is cool right up to the water pump.
I did have trouble last year with a sticking thermostat but changed it. I think the thermostat is sticking again because there is a lot of pressure coming out of the block at the pump bypass hose even after draining the radiator.
Even when thermostat is open the bottom hose is cool, any suggestions please ?
 
Last edited:
Sounds like stat to me
200 is so cool running its amazing, I once fitted new stat and drove 12 miles to work, got there thought old girl smells hot must be new stat making the engine run at proper temperature, so 8hrs later drove drove home and it got quite hot, so removed new stat and tested it in the kettle it didnt work at all! old stat back in and spent an age trying to find a new waxstat for it, found one and its been fine since.

Rad hot at the top and cool at the bottom is quite normal and shows you the rad is doing its job of cooling the water nicely, not forgetting the external temp this time of year as well.

Are you still running the viscous fan?
 
lynall said:
Sounds like stat to me
200 is so cool running its amazing, I once fitted new stat and drove 12 miles to work, got there thought old girl smells hot must be new stat making the engine run at proper temperature, so 8hrs later drove drove home and it got quite hot, so removed new stat and tested it in the kettle it didnt work at all! old stat back in and spent an age trying to find a new waxstat for it, found one and its been fine since.

Rad hot at the top and cool at the bottom is quite normal and shows you the rad is doing its job of cooling the water nicely, not forgetting the external temp this time of year as well.

Are you still running the viscous fan?
Click to expand...

Its the same in the summer ! never had a fan on the engine and never overheated even towing car on trailer in hot weather
 
Even so, the header tank should get warm and water should circulate through it. no water circulates from small pipe at top of radiator to header tank and it isn't blocked.
 
landowner said:
Even so, the header tank should get warm and water should circulate through it. no water circulates from small pipe at top of radiator to header tank and it isn't blocked.
Click to expand...

Hmm, I'm not sure about that. The header tank is a small bore spur off the cooling system and not a full on part of the circulating system.

Not quite as seperate as an older expansion bottle system that syphons coolant in and out of the system but not far off.
 
blue beasty said:
Hmm, I'm not sure about that. The header tank is a small bore spur off the cooling system and not a full on part of the circulating system.

Not quite as seperate as an older expansion bottle system that syphons coolant in and out of the system but not far off.
Click to expand...
Mine has a half inch (approx.) bore pipe from bottom hose to bottom of header tank and a small bore pipe from top of rad to top of header tank
 
Ive not looked to see if the header tank on my 200 has water movement whilst engine running, on my D3 I can see the coolant chugging around nicely.
Think my water pump is britpart and same as yours about 4 yrs old.
 
It all sounds pretty normal to me, although I'm not sure about the pressure build up. If you had excessive pressure from a head gasket failure I think you'd see it in the expansion tank. My radiator bottom hose gets just about warm even if the top one is too hot to hold (200 disco TDi, new rad). This is just the radiator doing it's job. I don't think there shouldn't be too much water flowing through the top feed from the radiator to the expansion tank - otherwise it would act as a by-pass for the radiator. Like many others on here I have found it can be difficult to get a decent thermostat, IIRC it took 6 tries to get one that opened at the right temp - and that include buying the reclusive waxstat version. The best one I bought came from Eurocarparts.
 
Pressure back from head through water pump bypass hose is worying because l had drained the radiator via the bottom hose and there was little or no water in it
 
Well I changed the thermostat today and no different, still overheating.
The thermostat opens and the top of the rad is hot but there is a definite area of the rad about a third of the way down where the temp changes from hot to stone cold. (rad not blocked)
The water pump is red hot as are the first two inches of the bottom hose below the water pump where it changes to stone cold again.
So bottom half (Approx.) of rad to water pump stone cold and every where else red hot.
Bought water pump today going to fir it tomorrow and pray :)
 
Well if water pump dont fix it, it might be head gasket time and that may explain the pressure in the bypass hose.
 
landowner said:
Had a head refurb with skim and gasket etc last year (even though it didn't need it)
Click to expand...


The head on my 90 and my spare head both have cracks between the valve seats neither pressurises, BUT if the cracks go deeper theres a chance they might.
 
Head was checked and tested by a reputable engineering shop (Oldham Engineering) . I had it done to be sure that my engine would be trouble free for the foreseeable future.
I don't think the head would cause the water not to circulate around the radiator
 
jamesmartin said:
i wouldnt fit either theres a very big chance
Click to expand...


The one on the 90 has been cracked for years, zero coolant issues, when I did the head gasket (due to oil leaks) on it a few years ago, I noticed the cracks and thought well it was not an issue before so back on it went.
 
New water pump gone on. Old one had a noisy rough bearing so it needed one.
Filled with water, bled it and all seemed ok, even the bottom hose getting like warm.
Drove it and it was ok for a few miles then the temp went up again. Stopped and the red was only half warm again so l loosened the expansion tank cap and it went back to normal.
When l filled it l did so with the pump by pass hose off till it came up then put it back and filled very slowly via the red with the engine running. But must have still been an air loc
Fingers crossed, going for a ten mile drive tonight
 
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