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Ok I will try to make it short, and if Im missing something just ask. Engine is a Mitsubishi 4G93 1996, did a rebuild myself, rings, bearings, head, the lot. Everything is running ok but the engine is overheating. I mean 248F overheating.
BUT i figured out just because i plugged a scan tool and watched the temps, cause temp needle goes up to just the middle of the range and then stops there. I went through the overheating guide in this web and i ran out of ideas:
- Air in the system: I tried really hard to bleed any air in the system. Did the funnel thing like Eric did and used the bleed off valve of the engine
- Coolant leak: none that i know, I put a giant cardboard in the floor under the car and and revved it some time, left it sit over night, cardboard came out clean.
- Pressure test: I couldnt do it, cause in my country the tool is ridicously expensive.
- Thermostat: this was my first guess, upper hose is too hot, lower hose is not even warm, but I removed the thermostat and is working ok, I purchased the original for this car from mistsubishi itself, no change.
- Water pump: I have pretty hot air when turning the heater on, and pretty cold air when AA is on, so i guess water pump is ok, also it only has 6-7K miles on it
- Radiator: Also new, less than a year of use, was replaced when i had a small crash last year (only both radiators damaged in the accident and both replaced with same spec as OE, also no obstructions
- Fans: both turn on, all the fins, but once they turn on, they will never shut off until I shut down the car and let it sit for hours
- Radiator cap: looks good to me, rubber is ok, no cracks no nothing, also i accidentally loosed it a bit when car was hot and boiling spray came out (no one was harmed fortunately) so its keeping pressure
- Checked heater core for leaks, none found
- Engine coolant sensor: Used two different sensors and i also checked with a termometer and the readings are ok
- Coolant: Using some quality coolant, it cames out of the car very clean
- Head Gasket: As i said, HG is new, both block and head were taken to the shop and skimmed. Power balance test is ok, no cylinder is weaker than any other, also when I remove the radiator cap while the car is warming up, no bubbles come out.
Currently i have the car on jacks and with the cooling system dissasembled. So pics or whatever is needed just ask.
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What signs are showing that the engine is overheating, just the scan tool data? I’d imagine that by 248F, the radiator cap spring should be open and venting excess pressure to the overflow bottle. Anything strange happening there?
I’m confused as to how the upper radiator hose could be hot once the thermostat opens, and yet the lower hose doesn’t warm up. If your coolant temperatures are approaching 250F coming out of the thermostat housing, it surely can’t be transferring all that heat to the radiator and coming out the bottom hose lukewarm. You should be seeing 185-200F into the top hose, and dropping approx. 10F by the time it gets to the lower hose.
Are you really super sure there is no obstruction in the radiator? If the upper hose is way hot, and the lower hose is not even warm, I don’t see how there could not be a blockage in the rad.
[quote=”Entangled” post=184484]What signs are showing that the engine is overheating, just the scan tool data? I’d imagine that by 248F, the radiator cap spring should be open and venting excess pressure to the overflow bottle. Anything strange happening there?
I’m confused as to how the upper radiator hose could be hot once the thermostat opens, and yet the lower hose doesn’t warm up. If your coolant temperatures are approaching 250F coming out of the thermostat housing, it surely can’t be transferring all that heat to the radiator and coming out the bottom hose lukewarm. You should be seeing 185-200F into the top hose, and dropping approx. 10F by the time it gets to the lower hose.[/quote]
Thanks for your replies.
Ok, signs of overheating are yes the scan tool data, the fact that it reaches working temperature SUPER FAST and even with the hood closed you can feel the heat coming out of the car and it didnt happen before, also as I said, once fan turns on, it never turns off again, and in the past it did.
The overflow bottle: never seen many action at all there. Its hard to see the coolant level when the car is hot cause more or less u have to put ur head in the way the fans are but never see any change in level there (and I marked the level when cold with a marker so I could see if there was a leak)
As to the hoses im puzzled, cause it was my first thought, thermostat. I removed the thermostat, tested the old one and the new one in hot water, both opened at the same time both are the correct graduation for the car: 180F
STILL i get the feeling that water is not circulating from the temperature of the hoses.
@relative4: if u mean obstruction like something preventing airflow, im sure its not, the car has a very big mouth in the bumper (there is a version with intercooler of this car) and is clear. If u mean obstruction internal, when I drain the coolant I do it from the valve at the bottom of the rad and I can see the coolant flowing from the top of the rad so i guess no obstruction there.As additional information. Its summer here.. about 90F all day long.
I’d suspect obstruction somewhere in the coolant flow. If the top radiator hose gets hot and the lower never does, it’s likely a matter of coolant not moving in a loop. Obstruction within radiator, obstruction within block / head, or water pump impeller issue. I’d try pulling the thermostat and running water from a garden hose with upper radiator hose disconnected. Using the upper hose as a funnel, you can force water to flush through the circuit either down through radiator as normal, or down through block in reverse. I know the water pump is likely driven off the timing belt and difficult to access, but with the system full of water and radiator cap off, you may be able to see a surge in the radiator neck when the car starts. That’s a good indicator that the pump has put coolant in motion of circulating, provided there isn’t an obstruction preventing it from doing so.
Sounds like you could have an air lock in your system. I would try bleeding the air off again as it sounds like you are not getting circulation through your system.
[quote=”Entangled” post=184524]I’d suspect obstruction somewhere in the coolant flow. If the top radiator hose gets hot and the lower never does, it’s likely a matter of coolant not moving in a loop. Obstruction within radiator, obstruction within block / head, or water pump impeller issue. I’d try pulling the thermostat and running water from a garden hose with upper radiator hose disconnected. Using the upper hose as a funnel, you can force water to flush through the circuit either down through radiator as normal, or down through block in reverse. I know the water pump is likely driven off the timing belt and difficult to access, but with the system full of water and radiator cap off, you may be able to see a surge in the radiator neck when the car starts. That’s a good indicator that the pump has put coolant in motion of circulating, provided there isn’t an obstruction preventing it from doing so.[/quote]
well water pump is driven by the timing belt. I did the water hose thing, poured water from the upper hose and it came out through the thermostat housing. poured water from top of the radiator, came off at the bottom without issues.
im going to throw something here, this engine has just been rebuilt, i mean less than 500 miles since new rings were installed, so i guess some overheating from the extra friction of a rebuilt engine is kind of expected. but i think what i have is too much. maybe im wrong
is there a way to check if the water pump is ok? I mean i can remove it but that wont tell me if it is moving the coolant correctly… I think i need a way of testing it in action. as I said before, i have good heat coming of the heater so at least one would think that water is circulating i guess… i checked and all the fins are ok, its a metal one, not a cheap plastic pump.
Im leaving here some diagrams of my cooling system so maybe someone can spot something i couldnt.
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