vt overheating at idle, please help!!

[trav27]

hey guys, i recently changed the water pump and radiator in VT. Tonight it almost overheated at idle, but while driving the temp goes right back down, then goes up again while idling. My guess was the thermostat not opening. Any sugguestions? Ive got a long drive tomorrow so any help at all would be appreciated!! Thanks, Travis

 

[edals]

Did you bleed the cooling system after you changed the pump ?

 

[trav27]

Did you bleed the cooling system after you changed the pump ?

My mechanic did, but i topped up the water last night and it started from then. Could it be air in the system?
Thanks for the reply

 

[Carl Blance]

take off the engine cover, the top hose connecting to the housing of the thermostat has a small nipple on top. Next use an adjustable spanner or a spanner ( do not use a flat head screwdriver to tighten or loosen it is easy to round off, and I'd avoid using a ratchet as you may over tighten and snap it) now take radiator cap off and start the car while the nipples loose and cap is off. When the temp start to rise coolant will come out of the nipple make sure most bubble are gone should not take that long and remember to squeeze the radiator hose to force it out quicker and keep coolant level high or more air is just going to go in the cooling system. Tighten nipple and wait a good 8 minutes till bubbles are gone or longer (make sure the radiator fan goes), if their is small amount of bubble appearing slowly put the cap on and I usually give mine a good thrash to see if it overheats, if its still doing it change the thermostat

 

[Brett_jjj]

If its getting hot whilst its sitting there idling, but running cool when travelling along, then Id be checking if the cooling fans are coming on..They should switch on once the coolant temp reaches a certain point. They will mostly come on when sitting there idling as theres no airflow going through the radiator whilst stationary.

 

[Alloytec]

Sounds like air in the system, this will cause a air pocket so to speak, and will stop your fans from switching on as there is water passing past the coolant temp sensor.

To bleed the cooling system correctly you need to raise the water level in the radiator use a upside down bottle with the bottom cut off, then have it to seal on where your rad cap goes, then crack the bleed nipple on the thermostat housing, undo the screw and then close it off once you have a uninterrupted flow of water coming out of it. Start car turn heater and fan on then switch off Repeat process 2-3 times.. and ensure the water level is at its highest possible level this will help the air bleed out.

 

[trav27]

Thanks for the replies everyone I made it there and back without too much drama, although on the highway the temp went hot. So i pulled over and cracked the nipple on the thermostat housing to let off steam. Which worked okay for a few hours. Although on the way back home, i had the heater on but i noticed when the temp started to rise, the heat from the heater would cut out and go cold, then come on again after a min or 2 then the temp would drop a few degrees [electronic temp on the dash].

Could that also be caused by air? Thank you

 

[Brett_jjj]

Yes, if its doing this then theres a problem with air trapped in the system. Face the front of the car uphill and use a cut off bottle to make a funnel to fill the radiator following the suggested method above in post number 6..

 

[trav27]

Thanks guys, i followed those steps and it seems to be working fine now. Although, my ac, heater or radio wont turn on at all now The thermo fan turns on at 104 degrees though. What could have caused that? A bit of coolant did spill out during the process though, im about to check all the fuses. Thanks

 

[trav27]

Actually disregard my last post! I just started it up again and everything was working perfectly No idea what happened lol. But thank you to everyone for helping me solve it