Coolant Level and Light

[scotinoz]

I would expect the opposite in terms of little flow to the header tank when the engine is cold. That is the purpose of the thermostat. The thermostat will restrict flow to circulating coolant around the engine block only for quick warm up until the coolant warms up to then open the thermostat to allow coolant to then circulate through the cooling system. That is why I wondered about a sticky thermostat if the engine temp went intially high then settled back to normal. Now if there is little flow to the header take when engine is warm, it could be a number of things such as air locks, dodgy thermostat and possibly the water pump.
Anyway all the best with it.

So you would expect little flow initially and more flow when warm?

[Silver Caravelle]

Correct, as it warms up one would it expect more flow as thermostat fully opens and pressure to then build in the expansion bottle when warmer. If it gets too hot beyond boiling temp, the coolant pressure is going to be relieved via the cap.
Ordinarily it should be below boiling point at 90c and no coolant loss through the cap ( the nature of a sealed cooling system expanding and contracting). So if there is good flow when warm to the coolant tank, it is unlikely to be the water pump unless it can be ascertained the pump is weeping or a noisy bearing. Where as a sticky thermostat is a cheaper option. Maybe remove the expansion bottle cap and run the engine an observe the flow into the bottle as it warms up. I think it will be visible to see coolant flowing/ returning to the bottle. But obviously put the cap on if the coolant starts flowing out of the bottle when warming up and avoid burning yourself in the process! I would be suspicious of a sticky thermostat given the initial higher temp and returning to 90c normal temp. Perhaps also monitor for a while to ensure no coolant loss. Of course if you still aim to change the timing belt and water pump given unknown history, all this will be checked as part of the process.

[scotinoz]

took the car for a drive today and all seemed fine, got home and stopped the van, checked the level looked ok so relieved the pressure by gently opening the cap. As I opened the cap as normal the pressure starts to vent but it vented underneath the bottle i.e. nothing coming out from the cap. Is this normal? Also while running I took off the oil cap and noted a good flow of air coming out here much more than I thought, is this normal?

[Silver Caravelle]

I am unclear regarding venting below the bottle? For example is it venting out of where the bottom hose clamps to bottom of the bottle; a possible leak there? I can only suggest look for dried coolant residue around hose openings to the coolant bottle to rule out any sort of leak and continue to keep a close eye on the coolant level that it is not disappearing somewhere.

If the temp is stable and seemingly no coolant loss and the thermostat is not sticking, perhaps monitor for the next few runs or check with a mechanic to be doubling sure.

After a good run there would be a 'minor level' of air flow bowing out of the oil cap opening. It is hard to gauge though without viewing it whether the level of air flow you indicate is normal though. If it is really blowing I would not consider this normal. Be worth a mechanic commenting on this as well.

[scotinoz]

I am unclear regarding venting below the bottle? For example is it venting out of where the bottom hose clamps to bottom of the bottle; a possible leak there? I can only suggest look for dried coolant residue around hose openings to the coolant bottle to rule out any sort of leak and continue to keep a close eye on the coolant level that it is not disappearing somewhere.

If the temp is stable and seemingly no coolant loss and the thermostat is not sticking, perhaps monitor for the next few runs or check with a mechanic to be doubling sure.

After a good run there would be a 'minor level' of air flow bowing out of the oil cap opening. It is hard to gauge though without viewing it whether the level of air flow you indicate is normal though. If it is really blowing I would not consider this normal. Be worth a mechanic commenting on this as well.

Found the venting location, the bottle vents through the cap but the liquid comes out one of the holes in the bottom which is as per design.

[scotinoz]

So water pump and thermostat replaced along with timing belt. Though I had solved it as van ran fine for a few journeys, however when loaded up for camping and we hit some big hills I had the coolant bottle pressure issue again. Interestingly it seemed to take longer for it to happen. I though it could have been an air lock as the the hot air seems to come and go from the vent when up HI, but now having vented it off numerous times I am discounting that. Could it be the head gasket? Van is running fine apart from this issue with no smoking or hesitation. Coolant looks clean and pink. Any thoughts as to whether a heater matrix restriction could cause this over pressure?

[Silver Caravelle]

Assuming the new water pump and new thermostat are all good, that should rule out those as the culprits. And assuming the system has been fully bleed properly, there should not be any airlocks in the cooling system. Perhaps double check the coolant bottle cap is fully closed until it is clicked tight.

If it was a head gasket, typically there is going to be coolant loss and potentially dirty coolant. Can only hope it is not this!

Recheck all coolant hoses and clamps to ensure no pin hole air leaks, and/ or coolant leaks.

The only other suggestions I have is the aircon and main radiators and whether there is a blockage ( probably unlikely) or too much crap or insects on the outside of them reduciing airflow and therefore cooling efficiency.

Maybe re bleed the cooling system (with heater turned on to allow full circulation of coolant ) and also run to operating temperature ( stationary) with the coolant bottle cap off and then observe coolant starting to rise to vent any air bubbles and then put cap on and fully close it. Hopefully there should not be any air locks.

Are both radiator fans kicking it when they are supposed to?

Scott.

[Silver Caravelle]

Gday,

I noticed your other posts today regarding installing an oil cooler. Did you rule out the above suggestions and your concern regarding the head gasket? Any coolant loss?

There must be an underlying cause of the cooling system over pressurising without having to resort to an oil cooler. Maybe add a new coolant expansion bottle cap to rule out unnecessary coolant release from the bottle. Apart from that, I am all out of suggestions!

Cheers,

Scott

[scotinoz]

I have ordered a gas tester kit for CO2 in the coolant but still not got to the bottom of the problem. Agree I should not have to install the oil cooler although I would like to lower the oil temps anyway so its a no regret upgrade. I will probably fit a new cap as well as its too cheap an option to discount. I don't appear to be losing any coolant although to be honest I am leaning toward a head gasket issue, albeit a minor one it would appear as the van runs fine and is ok for hours of driving when not working hard.

[scotinoz]

Does anyone know if the coolant bottle cap just has a pressure release valve for over pressure? Is there a secondary valve or function for any purpose?