I have a 1999 Chevy Blazer 6 cyl 4wd with about 116,000 miles. Recently when I’m driving, the temperature needle starts to slowly move up from middle position (210 degree) all the way to the very high temperature position(very close to 260 degree color alert temperature). I turn the car off before it reaches the color alert position because I don’t want to know what’s going to happen to the car if it overheats.
If I sit in the car and just let it idle, everything is in the middle position. But when I press the gas pedal while it is still in park, the temperature slowly starts to go up. And when I turn the car off before it reaches too high temperature, I think I hear some kind of fluid flowing sound, not sure what it is. There are 2 large coolant hoses that connect to the back wall. One of them looks very white, is this normal?
What do you think the problem is? I’m looking at several possible reasons like coolant problem, thermostat, radiator, water pump, coolant temperature sensor. I checked the coolant level in the radiator and it seems to be at the max line. I don’t see any fluid under the car so probably not leaking. Maybe a clogged radiator? How to check if it’s clogged or not? How to check if it is part problem like thermostat, sensor, etc? I am not good at diagnostics.
Also, does it matter if the oil was last changed about 3,800 miles ago? last changed April 2022 so almost 2 years ago. The reason’s because the car is usually driven very short distance between work and home so it’s mostly just sitting there, as you can tell by only 3,800 miles in 2 years time. Totally forgot about doing oil change. Do dirty oil and clogged oil filter affect car temperature?
Is it possible to narrow down to exact problem based on the symptoms in my post? I’m not good at diagnostics so all I can really do right now is do cheap fixes and work my way up in cost. So I guess start by doing a coolant flush, next change coolant sensor, next change thermostat.
The radiator was replaced in 2018 so about 6 years of not changing coolant. So maybe coolant got too dirty and clogged up the radiator?
Add one more to your list… the fan clutch. It is a big round silver thing that is between the water pump and fan. It has a bi metal spring that engages the fluid filled clutch and makes the fan turn faster to cool it. Given this truck is 25 years old it is probably dead.
I had the opposite symptoms when the fan clutch failed on my GMC pickup. The fan would become stuck and always going. It sounded like freight train and dropped the engine temp even lower than it should be running at. The clutch would never dis-engage and allow the fan to just spin freely at highway speeds - it was always being powered by the drivebelt.
An annoying but safer failure mode! (sounds a bit like a helicopter taking off) The truck just sucks gas when that happens.
In your case the bi metal spring likely broke. They can leak out over time or jam in the open position which would give the opposite failure…and far worse… problem of overheating.
When my fan clutch failed on my truck, open was the failure mode. Problem was, I could NOT find a proper operating clutch from any source. I tried 3 different sources… no luck. I ended up installing dual electric fans.
I would guess the lower radiator hose is collapsing when the engine is at higher revs. Since oil changes were forgotten about, hoses are likely original. Many have springs in them to prevent this.
The radiator doesn’t have a “max line”, it should be completely filled to the top. If the radiator is full, it seems like the thermostat is not opening.
Good ideas above. Lots of possibilities for this symptom. My first guess on reading your post is the cooling system may not be maintaining pressure correctly. If it is supposed to hold pressure to 15 psi, but actually only holding to 8 psi, this symptom could be the result. You might try replacing the cooling system pressure cap. There’s at least some chance that will do the trick. If not, you could hire a shop to test the ability of the cooling system to hold pressure. This is a commonly done shop test. If the pressure is ok, they can continue with the other cooling system tests, air pockets in coolant, fan speed, etc.
Clutch fans can be tested by trying to turn it by hand and seeing if it drags. I’ve only had a failure of it being on constantly causing a roaring sound and excess cooling. Radiator temp can be checked with a heat sensor to see if there are warm or cold spots or checked fir being full of bugs, where ya gonna start on a system not serviced for years though?
