Over heating problem

[Tamkat]

hi all,

I have a 93 VR V6 auto. The bloke I bought it from cooked it pretty bad. I have redone top end with new gaskets etc. I flushed radiator, and replaced hoses. She now runs really well except that the temperature will rise to almost hot then drop back to normal and continuing to do this over and over again. Not sure of water pump might be on its way out or if a sensor has gone, or maybe even a relay. Any thoughts would be much appreciated.

Thanks.

 

[ari666]

is there a special flushing technique for these? sounds like pockets of air in the cooling system. usually you just find a steep slope, jack the front of the car up so the rad cap (filler point) is the highest point, turn the heater on full blast, then run the car and fill it with coolant. but some commos are non return, and will need bleed points opened to get all the air out.

failing that, the thermostat could be playing up. ive had a few that were dead straight out of the packet. theyre sealed with wax, so if they take a hit in transit before you buy it, it can damage it. take it out and dunk it in boiling water to make sure it opens and closes properley.

what temp thermostat did you put in it?

 

[Wozza]

The yoyo effect pretty normal on a VR as they only have a single speed fan...basically should run around 3 tenths when driving around (gauge is marked in tenths) when sitting at lights on a hot day will raise steadily but not fast to about 5 and 1/2 tenths then fan kicks in and temp should drop to just under 4 and fan cuts out....repeat.... if its going over 6 tenths then the fan is stuffed or on the way out, radiator is blocked or not allowing sufficient airflow through,pcm temp sensor is not sending correct info or cluster temp gauge is reading incorrectly...If your temps are going up real fast when sitting at the lights but comes down to normal when driving..most common cause is water pump blades have corroded away...

 

[Tamkat]

Just got a thermo from super cheap. Never had a problem with new ones before. Will check it out though.

 

[ari666]

cheap thermo fans are too big for a regular rubbish bin, i suggest finding a skip out back of supercheap to throw that into.

 

[Tamkat]

I was driving on highway sitting on 100km/h and watching temp go up to just under hot then drop to normal running temp. Is doing my head in!!!!!

 

[Wozza]

I was driving on highway sitting on 100km/h and watching temp go up to just under hot then drop to normal running temp. Is doing my head in!!!!!

air in the system or faulty thermo....you should always boil in water on the stove a few times before putting them in, to check that work ok and to bed em in per say....