My daughter has a 97 3.0 CL. She was having an overheating issue with the original engine. It had a lot of miles...suspected a blown headgasket. Neighbor put in a used engine and still having overheating issues. Replaced water pump, radiator and thermostat..more than once. Have had the car running in the driveway to get up to operating range and both fans come on, even tried with air on and both fans came on. The car wants to overheat when in a drive-thru and when in very slow traffic. My daughter was complaining of some clear, cold water hitting her foot once in a great while so I had Pep Boys check the heater core. They could not find any signs of any leaking and core was putting out 90 plus degrees. They did mention the air conditioner was shot. I was told they also did a red dye test and found nothing. Since the same scenerio seems to be happening in the second engine as the first, could it be a faulty radiator fan module, etc? My daughter said she hears the fans on when sitting in the drive-thru, so I don't know what to think anymore. Someone...HELP!

 

If you think it has a bad head gasket you buy a $20 compression tester and test the engine. You don't replace everything on a whim. You isolate the problem.

 

Pop radiator cap check for bubbles. Try bleeding car by putting funnel in radiator and try to have someone in the car hold it at 2k rpm and be ready to add fluid.... Go through 2 fan cycles. This should get all the air bubbles out etc. Might want to try some radiator cleaner do flush. Purge like I said. You could also just drill holes around your actual thermostat to just by pass it I think. They do that if you are bypassing the idle air control valve ..... Maybe. Might have to double check that

 

As far as compression test.... I think you would want to do a cylinder leak down test. I've never done one are they done with the same tool? Listen for air through exhaust, intake, radiator cap, oil cap

 

 

Took car to PEP Boys...they had already done a pressure test, found nothing. This time they did a block test which showed nothing. They said there was no chemical change in the test. I wondering if the radiator fan module could be faulty? The fans do come on when I turn the air on but I wonder if they don't come on when needed at very low speeds...drive-thrus, etc.

 

My guess is you got a partial blockage somewhere. Normally this would occur in the radiator. You could even have a bad water pump.

Obviously if the fans are coming on that kinda rules out the fans....and the fan module...as well as the fan switch...etc etc

 

As I mentioned in my original post...it has a new radiator, water pump and thermostat. Everything has been replaced in the last month. Thanks.

 

Just me but.....please confirm the fans come on when the AC is off. You stated they do come on with the ac but never have confirmed that they do so when it is off.

I think "holmes" miss read that part.....or I did ?

Just because the fans come on when the ac is on does not mean that everything is ok with the cooling fan system.

 

 

Only thing I would say is make sure all the cooling system parts you put in there are Honda OEM. Anything less could be bad out of the box. Also, when it does overheat immediately look and see if the fans are on. If not, then the fan system is faulty. If they work then check the lower radiator hose. If still cold then the thermostat is bad.

 

Happened to me once, after changing almost everything (radiator, thermostat, thermo switch, fan relays, head gasket) still experiencing overheating and loss of water in the reservoir. What I did was to flush the cooling system.

Take out the thermostat, remove the upper rad hose then insert hose into upper rad hose, flush with water till water from the thermostat housing is clear. From the cabin, switch to full heater then repeat process of flushing. Do the same thing with the radiator, insert hose on the filler neck and open drain plug and remove lower rad hose, flush with water till water is clear. After that, put everything back then fill with coolant and distilled water, bleed the system, then let it run for to fan cycles, refill as necessary. This solved my problems. HTH.