Help Troubleshoot Intermittent Overheating

jbstein · #1 03-21-2015, 01:56 PM

Vehicle Description: 99 Ford Ranger XLT V6 3.0L Flex Fuel, 163k miles.

Hello everyone, my 99 Ranger has been having intermittent overheating problems for the past 2 - 3 months. It seems to have started to overheat about once a week after having it into a mechanic for a tune-up. Knowing that it intermittently overheats, I watch my temp gauge like a hawk. When it begins to overheat I seem to be able to slow down for a few minutes or pull over and the temp drops right back down. I've tried to avoid highway driving and am typically going 40 - 50 mph when the overheating happens. It doesn't seem to matter how long the trip is. For example, sometimes I'll start the engine cold and drive 6 miles and then it will begin to overheat. Other times I can drive 20 - 30 miles and nothing happens. One day a couple weeks ago I was driving to work and it overheated and it didn't want to cool down so I had to pull over for 15 minutes and this time my coolant was boiling/bubbling out of the overfill tank. I took it to the mechanic that same day.

I explained the symptoms to the mechanic and he performed his work. It was well overdue for a coolant flush so I received a coolant flush in addition to a cleaning treatment. A pressure test was done on the cooling system and it passed. In case the overheating was a head gasket problem, the mechanic performed a block test twice, passing both times.

Received my vehicle back from the mechanic knowing it passed both of those tests. I was hopeful my coolant was so old that maybe I have a blockage preventing proper circulation. Truck ran without issue for a couple days then day 3 it began to overheat again on the way to work. Another week went by without issue and then another day it began to overheat. I have messaged back and forth with the mechanic and he says this really sounds like a head gasket issue, but we don't have any evidence to confirm it.

I'm trying to re-produce the exact scenario that causes the overheating and I'm starting to think it only begins to overheat when my heater is on. The last overheat was a cold morning and I had the heater turned on. I haven't had the heater on over the past week without issue.

What does everyone else think?

I was surprised the mechanic did not replace my thermostat just in case, but I have a new one I'm planning to install. Also have a new radiator cap that'll be put on today.

Thanks in advance,
jbstein

FUzzyBUnny · #2 03-21-2015, 02:52 PM

My first thought while reading your post is a sticking thermostat. A head gasket would have showed up in the leak down test as would a radiator leak or water pump leak. I bet you throw that new thermostat in and will be fixed.

Might also be time to find a new mechanic.

GLH · #3 03-21-2015, 02:53 PM

Could be he fixed the initial problem with the flush and now it has air in the system causing the symptoms.

damned225 · #4 03-21-2015, 07:37 PM

I had the same problem in my 99. It turned out with mine, it was the water pump. Changed it and filled it with coolant and ran fine. But check your thermostat, and try bleeding the air out before you try the pump.