GeekDIYMechanic - Cooling System Overview GeekDIYMechanic - Honda Overheating Case Study EricTheCarGuy - How To Perform a Compression Test EricTheCarGuy - How To Solve An Engine Overheat ConditionMy friend calls me to tell me that he is seeing a coolant leak every time he parks his car. But, he couldn't seem to find the exact source. He wanted to know if I had any suggestions to find source of leak. I suggested the following general procedure I use to find leaks:
My friend followed this procedure and found that the leak was coming from the lower timing belt cover, which highly implies that the water pump is having issues.
About three weeks later during a hot spell, my friend calls me to tell me his car overheated again. This time he immediately pulled over and parked the car.
I was like no way. In my mind, I felt I let him down. I kept reviewing all the tests I previously performed. Again, one test I should have done was to pressurize test the system, but I felt running the car for over 20 minutes would have accomplished the same thing.
Later that night we both met at the car. I was assuming the worst, of course. I suspected one or more of the following:
The first thing we did was to perform a visual inspection. We noticed that there appeared to be residue around the thermostat housing, but we could not see the source. Using a cooling system pressure tester, we pressurized the cooling system from the filler cap. There it is. We could not even get up to 9 psi before we heard hissing. Although the sound seemed to originate from the thermostat housing, we couldn't find the source. We then added coolant to the system so we use the coolant to show where the leak was coming from. After filling the system, we again pressurized the system. Found it. The heater core supply hose right under the distributor had a 3/4" slit in it. As luck would have it, the leak shot straight onto the thermostat housing.
After spending 30 minutes to remove the factory installed spring hose clap (because the clamp spring head faced to the inside of the block making it very difficult to access), we cut the hose, used a new clamp, and reinstalled the hose. We then topped off system and pressurized the system. All was good.
Just to be sure, we ran the car for about 20 minutes to get the engine up to temperature and cooling system up to pressure. We also verified that thermostat opened, and that the water pump was pushing water through upper radiator hose.
I recommended that upper radiator hose, lower hose, heater core supply and return hoses, plus other hoses be replaced. I’m guessing he will do this over time.
1999 Honda Civic, engine D16Y7, overheated during a trip involving bumper to bumper traffic on a very hot day.
I happened to call a friend of mine, and in the background, his wife said, "hey, aren't you going to tell him?" Nervously, I asked him what did he needed to tell me. I thought for sure I forgot to do something.
He told me that his car overheated while driving around town in traffic. He indicated that the temperature gauge was pegged hot and that the radiator overflow tube blew off the radiator. Since he indicated that he drove the car with the temperature gauge pegged, his car might have a blown head gasket.
I broke the problem into two phases. The first phase was to determine if there was any damaged caused by the engine overheating. The second phase was to determine what caused the engine to overheat.
We started the job by looking at the oil for coolant. The oil looked ok. So after disabling ignition and fuel injectors, we proceeded to perform a compression test. All cylinders passed with flying colors. Wow. He dodged a bullet. It appears his head gasket was healthy.
After adding coolant, we then ran the car. We hooked up a scan tool so that we could monitor the coolant temperature, via the ECT. We then let the car warm up to 204 degrees, while touching the upper radiator hose waiting for it to get hot. The thermostat should have opened at 190. But the upper radiator hose never warmed up, meaning coolant was not flowing through the thermostat.
Well we know one thing. Coolant isn't passing through the thermostat. But that could be caused by a thermostat being stuck closed, an air pocket right behind thermostat, or the coolant is not being pumped. One simple way to test if the pump is working is to remove thermostat, reassemble, and run engine. If the upper radiator hose gets hot real fast, the water pump is moving coolant.
While burning our fingers, we did just that. We then ran the car and noticed immediately the upper house got hot and the radiator filler cap was pouring out coolant, indicating pressure.
So after installing a new thermostat, gasket, and radiator cap, we ran the car. We did the following tests with positive results:
So, in the end, the car was fixed with a new: thermostat, gasket, and radiator cap. All this for $26 and about 1.5 hours of work. An ASE would have diagnosed the issue in 15 minutes. But I'm getting quicker.