pressure in cooling system

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soontjen

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Location
west yorkshire
Hi All new on here but hope i can get some advice. P38 2.5 dse as had 2 new radiators in the past 5 years problems when towing twin axle caravan. yesterday over heated again checked waterpump and impeller totaly in bits put new pump and thermostat in but now goes int red after a couple of miles and coolant goes back into expansion tank. Tank cap working ok top of rad hot bottom not so hot. Thanks in advance Gary.
 
The rad is a twin pass in that coolant enters at the top at one side goes down to the bottom, across and up the other side. Are both hoses at the top of the rad hot whilst the bottom tank of the rad is cold ? If so then it suggests your rad is missing the baffle plate which seperates the two sections in the top radiator tank.

This allows hot coolant to enter the rad at one side of the top tank, nip across the tank and out the other side without going down to the bottom and back up. Would overheat pretty quickly in these temps.

I'd get the rad out drop a marble in one spigot, tip up the rad and if it falls out of the other spigot you've got issues. It should get stopped by the baffle plate.
 
If bottom cold and top hot that is a circulation problem, bad airlock, duff thermostat. Worth trying without thermostat in it to see if you get circulation. Make sure there is nothing blocking bleed off pipe from top of rad to header tank. Then with engine ticking over slow fill and squeeze hoses as you do it. Do that all first and see what you get. If all that fails J maybe correct.
 
If the bottom of the RAD is cold and the top is hot, I reckon Kungfu is right, it's the baffle in the top of the RAD. Certainly the first thing to check.
 
if the problem is this baffle plate,whats the fix?a new rad or is there another way round.my 2.5 also overheats not into the red but not far off.only does it when i,ve give it a bit of welly.
 
bart2181 said:
if the problem is this baffle plate,whats the fix?a new rad or is there another way round.my 2.5 also overheats not into the red but not far off.only does it when i,ve give it a bit of welly.
Click to expand...

Personally i would take a look at water pump first of all, they have a tendency to fall apart slowy or as in the OP case all at once. Over heating from this can crack the head if the overheat is not spotted straight away. On the BMW engine as with any other continuing to drive with the temp in the red is a fools game.
 
wammers said:
If bottom cold and top hot that is a circulation problem, bad airlock, duff thermostat. Worth trying without thermostat in it to see if you get circulation. Make sure there is nothing blocking bleed off pipe from top of rad to header tank. Then with engine ticking over slow fill and squeeze hoses as you do it. Do that all first and see what you get. If all that fails J maybe correct.
Click to expand...
Wammers that's what it was bad airlock thank f@~k. Thanks for the advice all.
 
Hi all me again, still running hot fitted new water pump,viscous fan,thermos and header tank top. Temp gauge at 12 o'clock but when i put heater control to low it goes up to end of the white line put heater back to 22 degrees or so and falls back to normal any ideas i thought it was fixed ?
 
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