coolant system circulation

**FLENG2008** · 02-11-2009,08:43 PM

hello all
i have a 1.9 tdi 115 and i could do with some of your ideas
i have a problem with the circulation of the coolant, i think its an air lock but i also think i may have a blockage and thats why i cant get the air out..
sometimes the heater drops cold, and when you check under the bonnet the top hose is hot along with a few other and bottom hose getts slightly warm at the top
from what i can feel the rad gets hot but not sure if this has a blockage as i cant seem to get this air lock out
after a run the bottom hose still doesnt get warm all the way down just still at the top and the expansion cap hisses air slightly
it never over heats but it has crept up over 90 degrees a couple of times when i peg it down the dual carrage way
i have had a sniffer test so its not the head gasket
i have had a cap fitted
i had a slight water leak but now fixed

not sure exactly what is wrong with it, i have a feeling its the rad thats blocked, cause ive never heard the fan switch cut in and the fresh coolant thats was put in recently has now turned a bit rusty coloured

anyway please help cause i dont want to get head gasket problems from a stupid air lock

thankyou

**zollaf** · 02-11-2009,08:47 PM

water pump, i think. these are self bleeding, so shouldny air lock. incidentally, the sniffer test( blue fluid that turns green/yellow)are unreliable on a diesel. if it does change colour, you have a blown gasket, if it doesnt change, it means nothing.

**kite** · 02-11-2009,08:58 PM

As Zollaf says waterpump, these are known to fail, also a good idea to change the stat

**FLENG2008** · 02-11-2009,09:35 PM

ok if you guys are sure ill go for that
is there anyway to tell for sure or is it trial and error..

**herby0001** · 02-11-2009,10:31 PM

My money is on the waterpump. There have been previous posts on the forum regarding the heater blowing hot and cold and it's been just that. The coolant isn't getting pushed round the system properly, hencte the hot & cold heater and dodgy rad.

**FLENG2008** · 03-11-2009,03:55 AM

thanks for the replies
appreciate it...

**FLENG2008** · 09-11-2009,02:29 PM

swapped the pump but the old one was fine

anyone got any more idea's

**FLENG2008** · 09-11-2009,08:07 PM

ended up being the thermostat

i was under the impression the thermostat was in the top of the top hose because the top hose got hot first
i didnt know until today it was in the bottom hose, i would of thought that anyone who knew that the thermostat was in the bottom hose would have pointed me in that direction first as the bottom hose only getting slightly warm at the top would have been a big indicator that the thermostat was blocked shut

so if your bottom hose doesn't get hot and your car overheats when going fast try your thermostat, it may not be water pump or head gasket like everyone assumes

**herby0001** · 10-11-2009,09:14 AM

Thanks for pointing that out. Kite did suggest the 'stat', though like you and without consulting a Haynes manual, I would have assumed it was in a top hose too. We live and learn.

**FLENG2008** · 19-11-2009,06:57 PM

i still have problems

sometimes the bottom hose gets hot but sometimes its stone cold
i think the thermostat housing maybe shot as i dont think the thermostat fitted in securley when i fitted it

and sometimes the heater fluctuate from warm to cold, they never really gett hott like my other tdi

just to let you know ive had a
thermostat
water pump
expansion cap
pressure test
sniffer test

i have a feeling i have a blockage or something simular, like radiator cause the coolant just doesnt seem to flow around like it should
any help appreciated
thanks for reading