# top coolant hose hot, lower cold



## omodos (Sep 24, 2007)

Oh man, I have had a mysterious coolant leak on my 04 x5 3.0d and thought I would follow advice here and search around for this, at the same time I started the x5 and left it idling for well over 30mins, whilst probing around I noticed the top radiator hose that goes to the expansion tank was warm and then got HOT. BUT the bottom hose was COLD, the car was idling for about 45 mins and neither the fan would kick in or the bottom hose heat up, so is my thermostat buggered?temp outside was 20C not too cold at all, should the fan have kicked in whilst idling for so long? or it being a diesel takes much longer?

I drove it around all summer in sweltering heat and never noticed if the fan actually came on or not, but having said that wouldn't I have fried the engine by now if the coolant was not circulating/thermostat not opening?

any advice would be much appreciated


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## Dan Voth (Dec 24, 2007)

*Sounds normal*

Not a Bimmer expert here...Just a long time wrench turner. What you describe sounds normal as long as your temp gage reads normal temp. Bimmers have relatively BIG coolant capacity and big radiators to boot. Normal path for cooling water is out the top (via the thermostat) of the engine and down through the radiator, so you should see a big differential in temp from the top hose to the radiator outlet (bottom hose). This indicates the radiator is taking heat out of the coolant....no worries. Regarding the fan not coming on...Has the car ever overheated?


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## omodos (Sep 24, 2007)

Dan thanks for the reply, car has never overheated nope?so when do you think the fan should come on?so they have large cooling capacity eh?hmmmm would like to know what the bottom hose of other bmw x5 radiators feel like after a drive or idling fro 45mins, am quite worried as one guy who replied said it is my thermostat, but surely car would have overheated if no coolant was getting to engine block, and perhaps it being diesel is not the same and engine needs to heat up much more before the thermostat kicks in?hmmm


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## Fast Bob (Jun 4, 2004)

omodos said:


> Dan thanks for the reply, car has never overheated nope?so when do you think the fan should come on?so they have large cooling capacity eh?hmmmm would like to know what the bottom hose of other bmw x5 radiators feel like after a drive or idling fro 45mins, am quite worried as one guy who replied said it is my thermostat, but surely car would have overheated if no coolant was getting to engine block, and perhaps it being diesel is not the same and engine needs to heat up much more before the thermostat kicks in?hmmm


The fan should come on when you`re sitting in summer traffic and other similar situations. A thermostat that fails in the "open" position will cause the car to take an abnormally long time to warm up, with little heater output for the first five miles or so....one that fails in the "closed" position will quickly cause an overheating condition. Since you have neither of those symptoms, it`s not likely a bad `stat.


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## omodos (Sep 24, 2007)

Thanks fast bob, took the car for a spin last nite, both highway and urban driving needle bang in the middle and the lower hose slightly warm.....so perhaps in hot summer weather the fan will kick in cheers


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## supdkup (Nov 11, 2008)

is there after market equipment to easily exchage the coolant ? the top radiator hose has a screw that is easily loosened , but the diameter of the opening is less than a half inch wide . has anybody sealed the coolant reservoir with liquid aluminum and had a good out come ???? thanks : supdkup


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