Engine Cooling problem
2003 Chrysler PT Cruiser 4 cyl Front Wheel Drive Manual 87087 miles
So I've had intermittent overheating issues for about 3 months now. It started when the car started to get hot while driving on the highway. I was able to keep the temperature at about the 3/4 mark on the gauge by giving it gas while waiting at stop lights and while cruising. If in neutral or a gear in which I didn't have to give it gas, the temperature would start to rise again. When I got to the auto parts store, the employee helped me figure out that the radiator cap was not holding pressure and we replaced that. I worked the air bubbles out of the system and eventually got the car to cool down properly to drive the 20 freeway miles to get home. I had no further issues after that. As a matter of fact, it would occasionally run lower than the normal temperature, then come back up to the 1/2 mark while driving on the freeway, causing me to think that it might just need a radiator flush if some particulate was clogging the system then breaking loose again.
About a month ago the check engine light came on and the temperature alarm came on as I started the car up first thing in the morning (cold start). I turned the engine off for about a minute and when I started it again the alarm didn't come on, but the engine light was on. I took the car to a small shop where they checked and cleared the code, which was due to the engine temperature alarm.
About two weeks ago, I made the same 20 mile drive that started all of this and the car started to getting hot just as I was getting off of the freeway. I was able to get the last couple miles to get to my destination by using the " give-it-some-gas" method I described earlier. I let the car cool off for about two hours, then drove half way home on surface streets watching the temperature the entire way with the gauge staying at the 1/2 mark the entire way. About 4 hours later I drove the remaining 10-15 miles on the freeway with no issues.
I live in Phoenix, so we had a 110 degree day last week and while driving on surface streets in stop and go traffic the car once again started to get hot. I got to a populated shopping center with the temperature at the 3/4 mark on the gauge again. I called a local repair shop for a price quote on the thermostat. Researching them on Google, they have been in business for about 35 years and received nothing but positive reviews from the people that had rated them. About 4 hours later I drove the 5 miles to get home with the temperature at the 1/2 way point. I took the car in the next morning and they replaced the thermostat for me.
While testing the repair the mechanic stated that he couldn't drive 2 miles from a cold start without the temperature skyrocketing up to above the 3/4 mark on the gauge. I paid for the repair, picked up my car, and verified his assessment. He stated that he thought that there may be a problem with the head or the gasket causing gases to escape in to the cooling system. He performed a dye test of the coolant, but it didn't react as though there were any gases in the system though. Checking the oil, there is no sign of coolant on the dipstick or the oil cap.
Once I got home I turned on the heater and couldn't really determine if the air coming out was ambient temperature or being warmed by the engine (it WAS 110 degrees outside). I also tried to see if there was horizontal fluid flow across the the radiator, but couldn't see anything moving when pressing on the gas. I decided to have them replace the water pump, belt, and tensioners as a gamble over the head/gasket, but the problem persists after that repair.
Currently the car will sit idle with the A/C off for about 20 minutes, start to heat up to normal operating temperature during that time, then start to heat up EXTREMELY quickly to the point of being over the 3/4 mark within 5 minutes of reaching the 1/2 mark. This process happens even more quickly while driving or with the A/C on.
A few last bits of information:
The mechanic used a temperature gun to pick up about 175 degrees on the upper hose and 145 degrees (approximate numbers) on the lower hose. The upper hose feels fully pressurized and too hot to touch as it gets about the 1/2 way mark on the temperature gauge. The fan comes on with the AC and it seems to be the high speed fan. I can't tell if the low speed fan comes on because I'm not certain what I'm checking for. I tried reseating both of the relays (I replaced a bunch of parts on a '91 Saturn that just needed the relay box seated and grounded properly a few years ago *grin*) The original coolant was orange/red, but the current mixture is green and shows no signs of rust in it. The replaced thermostat had a ton of corrosion products built up on it, but the replaced pump didn't show any real signs of wear or corrosion.
Because I'm over $700 in to attempted repairs and currently unemployed and running out of money to spend on this, any advice or assistance in figuring out the exact cause would be GREATLY appreciated.
P.S. I apologize for the length of the question. I just wanted to be sure to give as much background information as I could.
You need to make sure the cooling fan comes on at the right temps, there is a sensor on the block, usually near the thermostat, this senses the temp to start the fan. Most systems turn the fan on at about 224 degrees! Up to that range, your gauge should be in the normal range. I use an infrared laser gun to check the temp at the time the cooling fan starts. These are cheap enough to buy a small inexpensive one to test with. We know the fan works due to the fact it starts when the A/C is turned on. Make sure it's full too!
ENGINE COOLANT TEMPERATURE SENSOR DESCRIPTION The engine coolant temperature (ECT) sensor threads into the thermostat housing just below the coolant outlet connector ( Fig. 28 ) or ( Fig. 29 ). New sensors have sealant applied to the threads. The ECT Sensor is a Negative Thermal Coefficient (NTC) Sensor. The resistance of the ECT Sensor changes as coolant temperature changes. This results in different input voltages to the PCM. The PCM also uses the ECT Sensor input to operate the radiator cooling fan(s), and send a message over the PCI bus to the instrument cluster for temperature gauge operation.