Wednesday, March 28, 2012 - 09:32 pm, by: Ross Pesina(Ross79)
I've got a 91 Uzz31 and it randomly overheats. Car is completely stock. I have done a full service, new water pump, tensioners, radiator reconditioned with new top tank, pressure tested, etc. New thermostat also. I have re-sealed the plate on the side of the block known for leaking.
When I first drove the car after the service it overheated. I had it pressure tested, also did a coolant gas analysis to see if it's a head gasket. No milky oil, etc. After having it overheat a few times it decided to behave. I check coolant level every morning and it sits where it should.
Then a week later while driving to work it decided to overheat again. Switching the heater on dropped it a bar, but as I pulled into the car park I could see steam coming out. Once it cooled down I ended up having to add 4 Litres of coolant. This was over a week ago and so far hasn't overheated again. Any ideas??
Thursday, March 29, 2012 - 01:59 am, by: Jamie Richards(Nwb40gt)
check thermostat housing if sealed good if not fully sealed will leak very slow.You should check coolant pipe the run's under intake manifold those pipe have a tendency to leak after a water pump change
Thursday, March 29, 2012 - 08:50 am, by: Ross Pesina(Ross79)
It's a brand new top tank. Definitely hasn't cracked again. We had a pressure tester on it over a dozen times with both hot and cold engine. Does not lose any pressure even after 20mins or so. Not a single leak anywhere even thermostat housing is perfectly sealed.
I have even run it without a thermostat incase the new one is dodgy but it still overheated! So I put it back in. Was fine for about a week before overheating again. Now I've been driving it a week with thermostat back in and giving it the occasional workout and it has been trouble free.
Thursday, March 29, 2012 - 01:32 pm, by: James Johnson(Jimbo)
Ross, just making sure but I guess that the only way to correctly check the coolant level is to undo the 17mm bolt on top of the thermostat housing and have a look in there as the radiator cap is on the overflow bottle effectively. Also have you checked to see if the radiator is not blocked?
Ross Pesina DieHard Vic Soarer V8, Soarer T, Soarer TT, Supra TT.
Thursday, March 29, 2012 - 07:41 pm, by: Ross Pesina(Ross79)
Hi James, that's the way I fill it. I undo the big bolt on the thermostat housing and poor the coolant in. Once that's overflowing I top up the overflow to the full level. The radiator is like new. Fully reco'd. Although I will try dumping the coolant again, all I can think of if there's some rubbish flowing around occasionally blocking a passage and causing it to overheat due to lack of flow?
Friday, March 30, 2012 - 07:04 am, by: Tom Richards(Tomr)
you should have the engine running with the 17mm nut very loose so that air can escape. do not tighten the nut until a continuous stream of water is coming out, meaning all air is removed. (have the heater on when you do this)
Tuesday, April 17, 2012 - 10:41 am, by: Daniel Marshall(Ydass)
what mine would do is slightly leak from the gaskets that the water bypass is on from 1 head to the 2nd head theres 1 at front of engine and one on back of engine.
it would slowly leak and evaporate so i couldn't find the leak.
wasn't till i pulled out the motor and started ripping things off in frustration that i notice the gasket.
worth checking this and the hoses on the rear of motor/heater hoses and those little 9mm hoses what ever there for lol