So. A local 300zx members car keeps blowing out the water from the radiator to the overflow bottle then starts to over heat. Have tried different cap and has same problem. No water in oil. And no oil in water. Blows no smoke. I suspect a head gasket. Could it be thermo stat? Any other thoughts
Done a leak down test? Maybe get some test strips also and check the coolant for carbon deposits and Co2 levels. Would indicate if its hg related. No bubbles or anything when its running? Looking into the filler....
Try a new thermostat first. Radiator cap or loose tabs on cap where it fits on the radiator neck will leak also but if it is blowing out I would try a new thermostat before worrying about it being a head gasket. Cheers Dave
The neck seems ok. Cant see any damage and looks to seal tight. Anything else I can check I have put a coolant pressure tester on it. It does go down but very very slow. I can hardly see the needle move even after 30seconds at 15psi. Ill need to double check the bubbles. I have heard about these strips but never seen any. Any links to product names etc I can askfor ?
Bursons and autopro sell them. There are different ones available. So just choose wisely. Some measure the glycol level and other info you're not needing to know. There's no chance there is a huge air bubble in the system is there? What's the heater core like good condition? Heard of some sucking air into the system and causing grief. No dampness underneath the water pump. The breather ports not weeping or anything silly....
Ok ill checkout auto pro today. The only way there could still be an air bubble is if the thermostat isnt opening. I was putting craploads of water into it.
The coolant can expand fairly significantly once the entire system is up to temp. Is it possible the problem lies in the recovery system?
Give me some suggestions and things to check. I checked the cap and replaced with a good one. yet it still seems to fill the recovery bottle. leaving small amounts in the radiator to the point it will overheat. I have removed the bottle and inspected it and the rubber hose, it all looked ok and I refitted. Oh and I am using the 1.2 bar caps.
What time frame and conditions cause it to fill the overflow and overheat? You could try idling it up to temperature with the cap off to see if the temperature stabilises. Is it an NA or TT radiator?
Both OEM one about 12 months old (the one on there) or one much older (off my tt known good) Was a TT radiator. Started and ran it with no cap. it keep spitting water out. even when warm.
Its overheating and Im guessing its got a lazy or stuck thermostat. Or, less probable is the impeller on the waterpump has rusted away. Its rare but it happens in badly maintained cooling systems. Ill bet it doesnt blow water when its cold!!!! Only up to temp. With very slow movement of water in the system with a stuck thermostat, you can get localised boiling of water around the hot parts of the heads even tho the engine temp does not seem to climb that high. The boiling in the bowels of the engine simply expands to buggery and blows water out past the radiator cap and into the recovery tank yet the engine seems not that hot. E
seems to have made another leak in the radiator too. Im getting convinced its the head. Called repco today for the headgasket test kit, was 105$. Passed that for now. I will have a look around for some more, hopefully not quite as pricey.
Spits at a constant rate, no change with temperature or revs? Spitting with force or just overflowing/lapping over? It could be a failed pump and water in the galleys is boiling pushing water out, try running with the top hose off to see if it's pumping out? It's hard to judge flow or bubbling with the side tank radiators. Edit: tass beat me to it
So Tas was correct it doesn't overflow from a cold start? What's the service history like? if the 'stat has failed it might be time to start saving for a major service
