Hi guys, I posted a couple of weeks back about a possible cylinder head crack, a block test (rigged to do the test when under load/at speed without coolant getting into the chemical) says that the bubbles are not exhaust gas. Does anyone have any knowledge/theories about air gettin ginto the system when under pressure? seems bizzare but I can't think of how it would happen.
It's a townie 4x4 turbo diesel, with the correct radiator cap. Always pushing the coolant out of the expansion tank. No smoke, no loss of compression, no oil in the water, no water in the oil.
Any thoughts would be appreciated.
Thanks and regards
David R Millar
- (#7375) David R Millar, 27 Feb 03
"Always pushing the coolant out of the expansion tank"
Is the expansion tank filling and then discharging through it's overflow, or, just rising in volume?
Have you checked the integrity of the small discharge and suction hose which connects, from the rad/header filler cap, to the expansion tank and, also, the suction pipe within the expansion tank itself? The slightest air leak here will not stop coolant, on expansion, discharging to the expansion tank but, there will be no suction return and, at every "heat up" and "cool down", the expansion tank level will rise (if you are topping up at the rad/filler cap) The discharged, hot, coolant, in the expansion tank, will not return, as it should, when the main system cools but, a fair volume of air will be drawin into the system.
- (#7376) John Davis, 27 Feb 03
Thanks John, checked all the hoses you mentioned several times, living in hope it would be that. it takes about 50 miles of motorway driving to empty the entire engine, the internal heater fails then the temp gauge shoots up when the last of the water is gone. I've also watched the bubbles come up throught the test rig when I did the combustion gas test direct from the rad cap expansion outlet. My next check will be to see what sort of pressure is coming out of there, to see if it is inlet air (pressurised by turbo) or compressed by piston. does anyone know what sort of pressure the turbo can produce on the inlet air?
- (#7377) David R Millar, 27 Feb 03
David. The outlet pressure, of the turbo at full boost, is, I believe around 7/8 psi. It is volume rather than pressure developing here and the turbo is not a "positive" displacement device. If there were to be a crack or fissure in the head, adjacent to and contained within the inlet manifold area, as the hot cooling system can run up to the cap lift pressure of approx 13psi, the pressure of the coolant would overcome the lower pressure of the inlet air, and you would be likely to see steam from the exhaust as the coolant, combined with the turbo charged air, went through the combustion chambers. I don't think that the answer lies there.
Have you taken the thermostat out and checked it's operation? Even a failed and closed thermostat has it's jiggle valve to allow some coolant to circulate but, if this were to be blocked and there was no circulation, I suppose the boiling coolant could discharge from the rad cap valve, into the expansion tank. Although you mention no oil/water mix, have you also tried the test, with the rad/filler cap off, and a cool engine, to see if there is more than the normal amount of turbulence when you slightly increase the revs. If there is, then the head or gasket are likely to be at fault
- (#7378) John Davis, 27 Feb 03
John, I understand what you mean about the water exiting into the air intake, pressure there is just too low to get air into the water. Hmmm...
This is the second engine I've had, the first one died after overheating after it emptied the system too. The only parts not changed were the pump and the turbo.
I've renewed the thermostat, after checking for the symptoms with no thermostat installed; Symptoms were just the same. With a cold engine and the cap off, there is little turbulance, a few white bubbles, then it runs clear for as long as I want, only under lots of load, uphill or pushing it on motorway does the fault happen. I would realy prefer to not take the head off just for a look, unless I'm convinced the fault lies there. Any outside chances it could be something else?
- (#7379) David R Millar, 27 Feb 03
theories
If this problem is only happening under high load, there are some theoretical possibilities.
Clogged radiator. There may be blockages, or scaling in the cores of the radiator, that will allow a restricted flow of coolant which is sufficient under normal conditions, but is insufficient under high loads.
Failing lower or upper radiator hose. If the hoses feel soft when lightly squeezed, there is a possibility that when the thermostat opens and the coolant is allowed to flow, the negative pressure caused by the pump will force the hose to close slightly, thus restricting the flow. This may also happen as a result of a partially blocked radiator.
Automatics. If its an automatic, and the overheating episodes have been over a longish period, check the automatic gearbox fluid. Regular engine overheating can turn the light gearbox oil to the consistency of syrup. This in turn will then cause engine overheating. Its also worth checking the 4x4 drive box as well.
As its a diesel, if the coolant is being forced out by combustion gases, it would be discoloured by the sooty nature of diesel, as in a recent similar thread. If its not, and there is no cross over of oil and water, then your head may not be the cause.
- (#7380) dave Bright, 28 Feb 03
Thanks Dave,
I think this is the next step, to check the rads and I will try to get the pumpoff too for a good look inside.
I just have a doubt about it being the head, the cooling water (no antifreeze yet) is beautifuly clear and clean, no sign of contaminating exhaust gas which makes me think it is air. It dosent condense after leaving the rad cap, so it's not steam either. Will let you know what I find today. I'll check the transmision fluids as well. It is changing gear way too late and holding at high revs for too long, but I was leaving that to another day, perhaps it is connected. Will investigate...
Thanks guys,
- (#7381) David R Millar, 28 Feb 03
Hmmm...no antifreeze, that’s a worry. I know its a cost, especially if its being dumped out of your system, but I would strongly advise at least a little, or cheap antifreeze because of its benefits for anti corrosion and sludge inhibitors. With out it you may be adding to your woes for the future.
I looked up you first posting and at the risk of going over old ground, have noticed that you mention three things of interest.
It takes about 50 miles of motorway driving to empty the entire engine.
Have you verified that the viscous fan is working correctly? sometimes they slip at speed and cause overheating.
You mention a new radiator cap that has a float. The archives on Ace Answers suggest that the alternative radiator cap fitted with a float, is not ideal for the Townace.
Your original engine has been replaced due to overheating, and your new one is behaving similarly. I would suspect that the cause of overheating wasn’t a faulty engine, and if this fault isn’t rectified, your new engine is going to expire in the same way. Take care.
Checking the pump is a good idea as its a common component to both of your engines. When checking the radiators, logic would suggest that the horizontal one is the most likely. (In a vertical radiator, once the engine is off and the coolant has stopped flowing, any solid particles will fall out of the cores, into the reservoir at bottom of the radiator. In a horizontal radiator the particles will remain in the cores. Once solidified it will have reduced the bore, therefore restricting the flow).
- (#7382) dave Bright, 28 Feb 03
What baffles me about this is that air could empty the coolant out anyway. I can only imagine that even if you continuously pumped in 20psi air, or anything much lighter than water, then after an intial surge the "air" would just bubble to the top and vent from the cap. It's alarming to imagine emptying all the coolant from the engine, as liquid into the expansion tank, 50 miles down the motorway - it just doesn't make sense.
The nearest thing that I can suggest is that the internal vertical pipe under the cap of the white plastic overflow/expansion tank has somehow been fitted to the drain outlet rather than to the inlet from the radiator. I think that this would cause all the water to be gradually pumped out of the expansion tank and leave you with reduced coolant in the system, but not an "empty engine".
By the way Ace Answers OUGHT (I edit it) to suggest that the new Toyota radiator cap with the float IS the best one. It would help me to know where it suggests otherwise. And if there is a lot of "air" in the system the cap with the float will theoretically let it escape more easily.
- (#7383) Dave Mason, 28 Feb 03