Using cooland - thermostat probs?

[Timborooni]

Hi again all,

Well my problems just keep going and bloody going. I seem to be losing cooland out of my radiator cap as it has green colour around it, things i have done and things i have found follow:

Car:
1999 VT Commodore Wagon - 5 speed manual (factory) - V6

Replaced:
- New radiator
- New radiator cap (120psi)
- New thermostat
- New water pump
- New temp sensor
- New hoses
- New heater tap
- Chemical flush
- New coolant (as recommended on here)
- Bled air out a million times following instructions on here!

Problem:
When starting in the morning the temp (according to computer readout) is 14c, after driving for a while the temp goes all the way up to 104c then 1 thermo kicks in (never both even with air on) and then maybe another degree or two then the thermostat cuts in as the temp goes straight back down to between 87c to 93c in normal driving circumstances. When it is a cold day the temp can sometimes shoot back up again to around 104c to 106c when the thermostat opens and bang, straight back down to "normal" running temp. The coolant is always down about a litre or so (even though overflow is FULL) and i have checked a thousand times for leaks etc to no avail. The top and bottom hoses are always under pressure after reaching operating temp but most of the time the radiator cap is cool to the touch.

When i check under the hood after a days driving or so, there is a green residue around the radiator cap and some splash marks around the place (cold air intake etc). There isn't a LOT but obviously there is something not right. Have checked the overflow bottle which is ALWAYS full, never budges, and have checked overflow hose and tank and all is flowing through from radiator no problems. I have also checked for milky residue on oil cap etc incase of stuffed head gasget but nothing obvious.

Have read a heap of articles that you guys have posted about cooling systems etc etc and the different things to do and have tried EVERYTHING i can as per your instructions.

Now the questions are this:
- Could it be a dodgy radiator cap?
- Do i need a higher PSI radiator cap?
- Could the thermostat be dodgy?
- Should the temp be rising to 104c to 106c before thermostat opens?
- From what i have read 90c or around that is usual operating temp?

ANY help would be muchly appreciated as i am close to driving into a pole, apart from all the bloody money i have spent.. Although i must admit that i have saved quite a bit following instructions of this site, thanks for that!

Thanks again,

Timbo.

[TI3VOM]

My car had similar problems to what you described it turned out to be the water pump and the heater core

To check the heater core turn your car on let it heat up the switch the heater on is there a cat piss/coolant smell if so your heater core is on it's way out I hope not for your sake it's around $1000+ to fix.

I can't explain the coolant around the intake and radiator cap that ones a mystery.

[Tree cutter]

I would try another radiator cap because it should not let any coolant leak past externally. If the radiator cap leaks your cooling system will not suck coolant back in from the overflow bottle as your engine cools down , it will only suck air in. When you have air in your system the thermostat will not operate properly because it is not fully covered in coolant. I would also check the radiator where the cap goes on to make sure there are no bumps or hollows where the rubber seal on the cap touches ,as this will cause a leak.

[kniever]

im pretty sure the radiator cap is meant to be 135kpa for v6, it should say it on the sticker on the radiator cover just infront of where the power steering reservoir is.

[bundy_boy]

change the radiator cap to a 135 and see how it goes.

everything else you said sounds normal, the thermostat should open at about 91 or 92, and stay at or just below that during normal driving, however, when you are in stop start traffic or idling for longer periods then the temp will reach up to 104/105, thats when the first thermo fan kicks in (you should hear it click on), its also the fan that stays on all the time when you have the air con on.

the second fan doesnt kick in till 110 and higher, and unless its a really hot day and stuck in traffic, it should never reach that point, the first fan will most always be enough to bring the temp from 104 back to below 100

[graham7773]

check the radiator filler neck closely for cracks and have you had the radiator/cooling system pressure tested at operating temperature for leaks which you obviously have? I say at operating temp as there may be leaks which do not happen when the system is cold.

[Macca86]

+1 on the trying a new radiator cap with a higher rating. Also as said above have you have it properly pressure tested? Milky residue isnt the only sign that it can be a head gasket. My VU had no milky residue but just seemed to mysteriously loose coolant it it ended up being the head gasket

[wamboin23]

make sure the car you got is actually a recovery type car, should have it stamped on the top.

supercheap sold me a non recovery type the other day

[Timborooni]

Ok, have an update.... Went to local PEPs and spoke to guy there and bought a new radiator cap.. COMPLETELY different than the one i had on it, it is 135psi as recommended by you guys AND when i checked the packaging it came in it had that 135 was the recommended one for my model! To top itt all off, the TOP of the cap has a rubber seal where the 120 one (old new one) did not, it only had a brass looking thing this (i am hoping) will stop any coolant leaking out of the top of the cap and use the overflow as it is supposed to! The cap is slightly smaller height wise and the bottom rubber seal that actually seals the coolant in, is a little thicker. SO, am going for a longish drive today, topped up coolant, bled the air again a couple of times till constant flow from valve. Will let you all know how i go tonight when i get back.

Thanks VERY much for all the advise, as usual i am very appreciative.

Timbo.
P.S - Just read back through posts and what happened to wamboin23 looks like it might have been my problem, supercheap HAD sold me the old new 120psi cap and it was NOT a recovery one, the new one has recovery written on top and this would explain why this new one has a rubber seal on the top of the cap!