giperbolic

Overheating topic has been discussed too many times and unfortunately it's difficult to find any useful information among millions of "my car is overheating. help!" threads. I did a leakdown test: all cylinders were within 5% with no leakage through valves, headgasket, just very little through the rings (which I think is normal). I also did a compression test: all cylinders were 190+/-2psi. The car is still overheating while driving. I just flushed the system 2 times, vent the air: got it to normal operating temperature with cap off and temp selector on HOT, then put the cap (new cap) back on and added water to the expansion tank. I did run it on water (not antifreeze) just now without thermostat (which normally should keep you cooler than normal), but it still overheated 5 minutes into the drive. Expansion tank was almost empty (below low level) after 10 min drive. Radiator flows water pretty well (when I flushed it) and is uniformly hot, when engine is at the operating temperature, i.e. not clogged. Both lower and upper hoses are hot as well. Cooling fan does come on and it was on when I pulled over while overheating. I also checked grounds, since I read about bad grounds causing temp sensor fault. I'm thinking about doing a coolant test for hydrocarbons. Open to any advice.

giperbolic

anyone?

jadziasman

If you're sure the radiator is functioning properly you should check for combustion gas in the coolant. 99 out of 100 people will say you have a blown head gasket. But if that was the case you should have an overflow tank that is filling up with too much coolant - you should not be losing it while you're driving. Can't see how the overflow level could DECREASE when you drive - it doesn't make sense because the coolant expands when heated - your overflow tank could have a crack in it. Also doesn't seem possible that your cooling system pressure would be BELOW atmospheric - that would be the ONLY way coolant would be drawn out of the reservoir without a leaking tank.

Overheating has four primary causes:

1) Low coolant level - this is the case most of the time.
2) Restricted coolant circulation somewhere inside or outside the engine - clogged radiator is the cause most of the time (happened with my civic nearly three years ago and a $35 Chinese radiator from Ebay took care of that problem pronto).
3) Coolant picking up more heat than can be expelled due to: Exhaust gas getting in the coolant, An exhaust restriction somewhere preventing all the exhaust/heat from exiting the engine compartment, Or you could have a scuffed piston that generates more heat than the cylinder liner can remove.
4) Bad radiator cap - this doesn't happen too often.

Best of luck - I hope you find the cause and soon!

giperbolic

Thank you for your reply.

I did grab a good looking radiator for local junk yard, installed it yesterday and drove the car for about an hour with and without a/c, couldn't get it to overheat, temp actually read below normal. There was still some hesitation on acceleration, which before (while overheating) I thought was due to BHG causing bad firing on 1 or more cylinders. Since I couldn't overheat it, I thought that hesitation is caused by something else, so I wanted to check my timing first, let the car idle to get to normal temp, but 10 min later it overheated while idling (never happened before at idle), so the problem is still there.
Few weeks back I had all the cooling system apart and cleaned every path, replaced all the hoses, so I don't think it's restricted.
How accurate is the coolant test for hydrocarbons?
Does cooling medium affect the test results: I have distilled water now, I don't think having water instead of antifreeze should affect the test, right?

jadziasman

The leakage of gas into the coolant wouldn't be affected by using antifreeze and water or just plain water.

Don't understand why you are using 100% water though. You will overheat at a lower temperature with just water. Use 50/50 antifreeze to water. You shouldn't overheat at idle as easily.

giperbolic

I was draining it few times, didn't have that much antifreeze to refill, so I just used water. Today I did put a 50/50 mix, didn't overheat at idle, but overheated while driving again. I rented block test from Autozone, tomorrow I will try to test for exhaust gas in the coolant.

jadziasman

I didn't know Autozone had a block tester as a loaner tool. I think I might just try it to see if my engine has any issues. It has about 240K miles on it and misfires sometimes - mainly in the morning when its cool and damp - I dunno why. Maybe its the spark plug wires or something.

Your overheating issue is weird. You can also run a pressure test on each cylinder with a dual pressure gauge they sell at Harbor Freight. You can spot bubbles in the overflow if a cylinder leaks. Kind of the same as a leak down test???? I'm not too sure.

typr2nv94

Sounds to me like ur ect sensor is giving false readings. Verify ur temperature first with a laser thermometer (autozone, pepboys, kragen sells em). Point it at ur upper radiator hose and check the outlet temp before it hits the radiator. If ur gauge is showing overheating and the thermo is showing between 170 and 190, u should be fine, and the prob is ur ect which is the single wire sensor below the dizzy.

giperbolic

I found some debri in the radiator. I flushed it out and some small rust and sludge particles came out, I flushed engine with garden hose, but couldn't see anything coming out. So much for the 2nd junkyard radiator. I filled it up again with 50/50 and couldn't overheat at neither idling nor driving for 10 min, longer drive test to follow. I will get a $40 ebay radiator replacement anyways.
BTW, if you rent autozone block leak test (27145), you need to rent the fluid bottle (25739) as well, yes you RENT fluid, but you won't use more than 5th of the bottle. Well, I don't know about autozone where you live, but 2 stores I check around my house had that fluid, but it was barely blue, almost clear, so I couldn't read anything during the test. I went to napa and bought a bottle of test fluid from them (~$7), it's dark blue. When I tested with it, it turned green with a blueish tone = passed as per instructions. I confirmed the color change by testing exhaust gas at the tail pipe - it turned yellow = failed indication as per instructions.

mrfootball420

Have you checked your thermostat and water pump? Pull your upper Rat hose and see how well its circulating.

giperbolic

both brand new, overheating problem was not affected my removing/installing thermostat. Good flow, I think radiator has crap in it that I can't flush out. Didn't overheat on 10 min drive today with A/C.

mrfootball420

cars will overheat more at an idle because there is no wind to cool it down. The best way to test it is to step on the brake and then the gas to put a load on the engine and simulate going up a hill. Thats the best way to check for overheating. if you have good flow then the rat must not be clogged. Check the engine temp with a laser temp gun. How do you know its overheating? Also water boils at 212 degrees and to much water and not enough coolant will cause evaporation and loss of fluid level and then of course overheating.

EG9turbo

Are you sure your radiator fan is kicking on?

JDM_Frijoles

Buy a new radiator. Check your heater core for leakage. It could be leaking and causing the the coolant not to be under pressure therefore causing it to boil. Just my 2 cents.

jooky5

Test your thermostat