M

Muddyblue

New Member
I've had overheating issues on my Disco 300tdi for a while, the usual suspects have been changed but heard something lately which is new to me.
It only overheats at sustained motorway speeds, 65-70 mph, and I was told the thermostat housing could be porous, at these speeds when under load it can suck in air causing the overheating ?
Has anyone else heard of this ?
Thanks
Steve.
 
no never and system is running at 15psi ish when upto temp unless caps poor in whih case some water loss could be expected too shouldnt suck air in but leak water out,what were usual suspects ? have you felt the rad when engine warm to check its hot all over,do you check level with both bungs removed and fill to over flowing including expansion bottle
 
Basically the whole engine has been replaced ! Replaced the block beacause told that could also be porous. Mine had done 204k miles so replaced with one half the mileage but transfered all my original auxilliaries, so new head gasket, heads ok, new radiator and pipes, water pump is 12-18 months old, coolant is 50/50 mixed.
Systems been flushed several times and air locks bled out through top of thermostat, highest point ? Brass caps on rad and housing, replaced cap on expansion tank.
It's never leaked water or had oil /water contamination
The stat housing was transfered from my old motor and then found out about this query, I've replaced it but havn't been able to test it on a run yet.
 
never seen/heard of porus 4 cylinder block but occasionally can crack,still check rad even the odd new one can be poor (faulty baffles )check thermostat fully opens in boiling water etc,is engine geting hot ?check actual temps , is alternator overcharging on higher sustained revs as this can make guages read higher switches can be poor etc
 
Thanks for the ideas. I've swapped the dash gauges (just changed the whole binnacle) but nothing different so assume my temp gauge is ok. Have taken readings over several parts of the engine with an electronic temp gauge at "Normal" running temp, just need to be able to stop safely on motorway when gauge is saying "Hot" to compare. Have dropped stat into kettle and checked, all seems ok with that.
Will find someone local who can check alternator but its only a year old.
 
u didnt mention nothing about the temp. sensor(or have i missed it?) .... it could send wrong input to the gauge
 
hi when you say you droped themostat
in to kettle of boiling water and it opened
ok what temp was the water
i had a fault with mine also put it in boiling water
to find it wasent opening till it was over 100 degrees
dont know if any help thanks martin
 
hedge hopper said:
hi when you say you droped themostat
in to kettle of boiling water and it opened
ok what temp was the water
i had a fault with mine also put it in boiling water
to find it wasent opening till it was over 100 degrees
dont know if any help thanks martin
Click to expand...

Correct process is pan of water, thermometre, heat source and thermostat. Place thermostat and thermometer in a pan of cold water. Place on the heat and wait for temp to rise. Watch the stat amd the thermometre. Check the temp at the exact moment stat starts to open..
 
Have yu checked the RAD?? if all the fins have disappeared and or it's full of mud.that will cause overheating.
 
Dont forget thet the cooling system works under 1.4 bar all the time and the coolant flows continuously drived by the pump... so IMO this "boiling the stat" kind of test is not the best... unless u want to put some vegetables and meat there and make a thermostat broth:D
 
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