Help please!!!

My car gets warms slowly and then suddenly gets really hot.

If you stop and leave the car ticking over its fine. Still no hot air through fans but as soon as you drive the car it overheats again.

Thoughts on this would be greatly appreciated, I thought maybe a thermostat issue?? or possibly radiator???

 

Waterpump ??

Heater is circulated via bypass system, so either air locked or no flow.

 

sounds like an airlock have you recently had any work done on the water cooling system ie coolant change?

 

Now that is the question what it is,

I break scoobys i usually pick up ones with heads gone or big ends gone.

I picked this one up last night off a bloke have in a mid life crisis he had only had her for 4 weeks when this happened, he was told by a no mark mechanic who just popped the hod the head gasket had gone how he new that from just looking i don't know.
Im reluctant to scrap this one as its in good nic with only 80k on the clock and i may get more selling im only a pat time mechanic so im still learning on scoobys.

 

no heat through the heaters is lack of water getting to the matrix so there`s an airlock, whether there`s an underlying issue you wont know until you get rid of airlock

 

i would bleed the system as much as poss then start leaving the cap off and check that you have a steady flow of return water from the small pipe on top of the expansion bottle and the heaters get warm, once you have that make sure the level is all ok then put the cap on take for a good blat then check that there is not excessive presure in the hoses let it cool and recheck the levels and make sure the heaters stay warm.
scoobies can be a real pig when it comes to airlock i have found out so many times and they dont always show up at 1st

 

Cheers for that lads ill get out there in the snow and have a go

 

Can i *** get my it to warm up in side the car driving me mad now its snowing right i can get the pipes to heat up only when the caps are off once i put them on both go cold again am i missing a trick here

 

No heater = no circulation, airlock, blockage (in the matrix) or broken heater controls

Overheating, again look at airlock, no circulation or blockage (in the radiator)

Airlock can be caused by a leak in the system, lack of coolant, leaking waterpump shaft seal (sucking in air and causing cavitation) or blown head gasket(s)

If its been allowed to boil, then its probably popped the head gasket(s) anyway...you probably find combustion gasses are getting into the cooling system and airlocking it...with teh caps off it allows it to vent out the sytem which may explain why the heater works when the cap is removed.


You need to do a pressure check, and also a sniff test on the main coolant tank for combustion gasses.

 

Thanks for the reply sorry the heater doesnt warm up in the car at all with the caps on or off just the rad pipes heat up with the cap off.

If it snows much more i may be buried alive in the engine

 

try thermostat,mine went dodgy and wasn't opening properly just enough to get pressure but not enough flow to keep the temp gauge down normal.just a thought though.

 

Drain and refill S L O W L Y.

Do a search on here for how to.

Thermostats stick OPEN, which means that the engine doesn't get warm enough, not overheats.

 

did you solve the problem mate??