For the past couple of years my Z has had a bad cooling problem on long trips... Last 2 trips to Melbourne(latest this last weekend) it has boiled on way back, both times near Tarcutta and also near end of journey. Suspected leaks etc... Last night after dropping friend off he felt we should check the coolant again before I drove the final 40km home, to cool it enough to remove cap he sprayed water on the radiator while engine idled, after a few minutes he tried to remove cap.. no luck I then tried and had to overcome significant vacumn. I know the coolant can get out to the overflow bottle because on a long trip that overflows out into the guard and onto LH wheel. My theory is that I may have a faulty or incorrect Rad cap that allows the heated water out but will not return it when cooler.. allowing the engine to pump water out to the point there is not enough left to cool! Does this theory make sense? (does the description of it make sense!!!?
A few ways of looking at it Vacuum in radiator - good news - no leaks. Radiator cap issues- 1.Cap release pressure too high - doubt this would pump much into the overflow tank. 2.Cap release pressure too low - more coolant to overflow tank. Even with a low pressure cap there will still be a good vacuum seal when taking the cap off. Either get the cap tested or cheap enough to buy another cap. Have you had a close look at the cap. It could be the wrong type - as in not designed for overflow return. Cheers, Dean
My theory would be similar to yours, with one exception....... I think you may have an air leak in the overflow hose to the coolant bottle ( or an air leak at the radiator cap) either of which would allow the heated coolant to flow into the overflow bottle, but it would fail to return to the radiator because air would be sucked in instead. The return flow to the radiator is totally dependant upon there being no leaks of any kind in the hose or cap. If the fluid transfer is always in one direction (radiator to overflow bottle) then the bottle will eventually overflow onto the roadway.
Except... Good theory Lloyd.. Except if there was leak in return pipe, vacumn would not be an issue... Suspect there might be sludge and s&^t in overflow tank that might block return.. will investigate that!!
Split in overflow hose could be culprit as Lloyd suggests because - cooling down and hence sucking coolant (or in faulty case - air), normally takes place over a long time frame. Your test with quick cooling of the radiator might just outstrip the capacity of the cap to equalize pressures. Definately check hose & connections for leaks. Cheers, Dean
Overflow pipe, and return pipe, are "one and the same" on my car,.... so blocked pipe seems unlikely, as the coolant wouldn't get into the overflow bottle in the first place. Does your car have two seperate pipes, to and from the radiator overflow?
Only one pipe.. Have blown thru pipe and it seems intact... have not tried the reverse yet (don't want mouth full of coolant) Cap seems correct type(1.2Bar) and is a return type.. Ihad suspected that as well Dean. I suspect there is sludge or something in Overflow tank that blocks return... there was some resistance when blowing into tank
Ever thought that the thermostat is stuffed - replace the thermostat with new one, and while you have it apart check the water pump / impellor. Have the radiator stripped and rodded to remove any deposits in the tube. Coolant does have a limited life so replace the coolant with new Quality Coolant. replace radiator cap with new cap. Big job not really but sure does give you piece of mind when travelling knowing the cooling system is up to the task at hand. After doing this you should not have any further problems. Regards
Check the ovefflow bottle I cleaned out my overflow bottle and found a ball of crap which let water in but acted as a ballvalve in the opposite direction.
I'm with Cove. If you have never done it since your zed ownership (and it's highly doubtful that the previous owner has done it either) it might be time for some preventative maintenance. Tech article here for ideas.
Will work on bottle theory... Thermostat was replaced and pump checked last time this happened.. might go the rad cap cos it is cheap & easy but symptoms fit the water bottle theory! Thanks guys
What an awsome Tech article.. Mark, I just looked thru your overheating feature... That is just awesome!!! Will be a great help Thanks
