Smokydiesel Posted November 16, 2010 Share Posted November 16, 2010 Hi, I just swapped my thermostat for a new one because it seemed to be stuck open as the engine wouldn't warm up. (200 tdi, ex Disco engine) Replaced it with a 88 degree thermostat, but now the bottom radiator hose and header tank stay cold, even after a 40 mile trip. The upper hose is warm, not very very hot. Could it be that this thermostat isn't opening at all ?? Also noticed that the temp-gauge is now nearly in the red, with the old thermostat it would hardly move from the cold-position.... Thanks ! Quote Link to comment Share on other sites More sharing options...
Maverik Posted November 16, 2010 Share Posted November 16, 2010 Have you got the right temperature sender for the gauge? it being a disco lump and all? If the top hose is warm/hot then the thermostate is open, if it was closed then it would not be hot at all. Is your water pump healthy? and are you sure your coolent system is well bled? no air locks etc. My Disco 200tdi lumo gets up to temperature within 5-10 minuets of driving usually, doesn't take long at all, but according to my temp gauge it runns a little on the cold side, (needle nearly always sits to the left of center) which I have also heard this is normal for a 200tdi. Quote Link to comment Share on other sites More sharing options...
Smokydiesel Posted November 16, 2010 Author Share Posted November 16, 2010 Have you got the right temperature sender for the gauge? it being a disco lump and all? If the top hose is warm/hot then the thermostate is open, if it was closed then it would not be hot at all. Is your water pump healthy? and are you sure your coolent system is well bled? no air locks etc. My Disco 200tdi lumo gets up to temperature within 5-10 minuets of driving usually, doesn't take long at all, but according to my temp gauge it runns a little on the cold side, (needle nearly always sits to the left of center) which I have also heard this is normal for a 200tdi. Hi, Yes it would be the right sender, it's the one Steve Parker sell's especially for the Disco-lump conversion. Although I read here that some people have "strange readings" even with a SP-sender..... An air lock could very well be, i'd have to check that this evening. I'd expect the lower hose and header tank to be much cooler than the upper rad hose, but stone cold after a 40 mile trip ??? Is that normal ? Since the thermostat swap, the heater works a treat now !! Quote Link to comment Share on other sites More sharing options...
Smokydiesel Posted November 16, 2010 Author Share Posted November 16, 2010 Right, have been searching the forum. As I understand, a hot top hose and cold bottom hose/header tank, is just OK. Guess I'll have to find a temp-sender that matches my gauge AND give's a sensible reading..... Quote Link to comment Share on other sites More sharing options...
Maverik Posted November 16, 2010 Share Posted November 16, 2010 Right, have been searching the forum. As I understand, a hot top hose and cold bottom hose/header tank, is just OK. Guess I'll have to find a temp-sender that matches my gauge AND give's a sensible reading..... It does sound like your sender is doing strange things. A tip, if you think about where the water is flowing around the sysem it will help you understand why things are hot or cold. If you trace the coolent pipes on the engine you can work out where the hot water should be and shouldn't be. when the thermostate is shut, the pump circulates a relativly small amount of water around the jacket of your engine and through the cabin heater matrix, on the engine these are all quite small pipes... when the water gets hot, it pops the thermostate open which opens up a new circuit for the water to flow, this circuit had a much larger pipe diameter than the engine "jacket" circuit, which diverts the hot water into the bigger bore pipe as it has less resistance, so the hot water is flowing into the "top" of the radiator ready to be cooled down. When the water leaves the radiator it should be cold, or the radiator isn't doing its job properly. The header tank has a limited role is makeing sure that there is enough water in the system whern the water contracts and expands causing a volume change. This water in the tank doesn't really get a chance to flow around the coolent system, also if you see where the header tank supplies the system its just as the cooled down water exits the radiator so the header tank shouldn't get hot, it might warm up due to conduction/convection, but generally its quite cool. Quote Link to comment Share on other sites More sharing options...
Smokydiesel Posted November 16, 2010 Author Share Posted November 16, 2010 Thanks Maverick, You've cleared it up for me ! First thing now is to solder the joint I have in the sender wire, right now the 2 bits of wire are "sqeezed" together in a cable-clip. After that, I'll fit that extra earth-strap between engine and chassis....should have done that months ago... Let's see what happens. Cheers, Edwin Quote Link to comment Share on other sites More sharing options...
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