How do you know if the fan is working properly at speeds? 1990 k5 350 over heating at speeds driving for a period of time. New radiator, new thermostat etc.
CK5
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overheating issue
- Thread starter Justin Fleming
- Start date
At speed the flowing air should be cooling the radiator.
Fan would be for low speed/idle
Fan would be for low speed/idle
So I have no coolant missing, none in the oil, new radiator, new thermostat, the only missing link would be water pump.
The truck will get up to 230 or so driving over 10 miles and as soon as I slow down and drive a side street or parking lot is cools right back down to 210 where the stat is set....
The truck will get up to 230 or so driving over 10 miles and as soon as I slow down and drive a side street or parking lot is cools right back down to 210 where the stat is set....
I've seen lower radiator hoses get sucked shut at higher rpms and choke off the flow enough to cause only "high speed overheating"..some came with a coil spring inside them to prevent that--new hoses may or may not have one--I prefer to shove the old one in the new hose if possible to avoid that chance..
The thermostat might not be keeping accurate temparature control ,in my days of parts store counter work,I'd say thermostats were probably among the top 3 items returned as "defective"..
If you know someone with a heat indicator gun that reads the temperature of things,pointing it at various places on the radiator can help pinpoint cool or hot spots indicating poor flow--the radiator might be new but that doesn't mean it cant be blocked up..
The thermostat might not be keeping accurate temparature control ,in my days of parts store counter work,I'd say thermostats were probably among the top 3 items returned as "defective"..
If you know someone with a heat indicator gun that reads the temperature of things,pointing it at various places on the radiator can help pinpoint cool or hot spots indicating poor flow--the radiator might be new but that doesn't mean it cant be blocked up..
Let's start from the beginning. Why the parts change? When did the overheating start? Stock motor/trans?
Like diesel said, just cuz its new doesn't mean it's good.
Like diesel said, just cuz its new doesn't mean it's good.
It's been happening off and on for awhile now. The truck only sees about 5k miles a year if that. New parts were installed when old radiator failed, so while replacing coolany etc. I put new stat it, It all works just fine except when driving at speed for a period of time.
Do you have the old thermostat? As mentioned, pretty likely culprit, particularly when it apparently cooled ok prior to the radiator/thermostat change.
Water pump would be a real stretch. I recall hearing of exactly one that was so bad the impeller blades had rusted off, and it was a Ford. I've never seen it, and even with poor maintenance (IE, coolant that was never changed) I've not seen nor heard of other problems with the impeller failing. The belt drives the impeller mechanically, this is the impeller http://image.superchevy.com/f/8961879+w640+h426+q80+re0+cr1+ar0+st0/0408sc_pump_04_z.jpg So unless the impeller is just spinning on the shaft, or the impeller is gone, it has to move fluid.
Does the gauge seem to respond properly at startup and as the temperature climbs? Any chance you have a scanner or ALDL cable and can check the temperature the ECM is getting from the CTS?
Sure the gauge is accurate?(i didn't read all threads)
yes
It could be lots of things...
I hate to mention this,but I've seen a few engines that overheated only on highways after 15+ minutes of driving,and they ended up having a slight head gasket leak, that was letting some compression get in the coolant and foam up,which inhibits its ability to cool off the engine..it forms air pockets...
After several days of the engine overheating intermittently on one car (it did not do it every day !),one morning the owner noted when he went to start it up cold,the engine spun over a half turn,then "stopped",like the battery was weak,then it cranked over "normal" and fired up,and he saw a white cloud belch out the exhaust..
A friend told him the next morning to pull the spark plugs out before trying to start it and see if he saw any "green" on the electrodes..sure enough,there was some coolant on the plug in the cylinder with the gasket leak...strangely enough it had no coolant in the oil,nor did it pressurize the radiator or hoses and pop them,I have seen that more than once when its not a "bad" leak..
Hopefully its not that,and you'll find some other problem...
I hate to mention this,but I've seen a few engines that overheated only on highways after 15+ minutes of driving,and they ended up having a slight head gasket leak, that was letting some compression get in the coolant and foam up,which inhibits its ability to cool off the engine..it forms air pockets...
After several days of the engine overheating intermittently on one car (it did not do it every day !),one morning the owner noted when he went to start it up cold,the engine spun over a half turn,then "stopped",like the battery was weak,then it cranked over "normal" and fired up,and he saw a white cloud belch out the exhaust..
A friend told him the next morning to pull the spark plugs out before trying to start it and see if he saw any "green" on the electrodes..sure enough,there was some coolant on the plug in the cylinder with the gasket leak...strangely enough it had no coolant in the oil,nor did it pressurize the radiator or hoses and pop them,I have seen that more than once when its not a "bad" leak..
Hopefully its not that,and you'll find some other problem...
Start w/ the simple stuff. Make sure the rad fins are clear of debris, your fan should not be doing anything. Make sure the bottom hose isn't collapsing, there should be a spring in there to prevent that. You said you replaced the thermostat right? If you run the truck w/ the rad cap open are you seeing decent flow once the thermostat opens, and does the upper hose get hot?
Did you change locations for the heater core houses with the new radiator?
If nothing else was changed id start with a fiew Quickest tests, hold a high (2k ish) rpm . see what the hoses do before, during and after. If normal, Next would be to put the old t stat in. Or drill a small hole in the outer ring see what it does going down the road.
I played the water pump game, even thought to try a reverse flow pump.
Chevy pumps don't kill impellers, its bearing or seal failure 99% of the time they die.
If nothing else was changed id start with a fiew Quickest tests, hold a high (2k ish) rpm . see what the hoses do before, during and after. If normal, Next would be to put the old t stat in. Or drill a small hole in the outer ring see what it does going down the road.
I played the water pump game, even thought to try a reverse flow pump.
Chevy pumps don't kill impellers, its bearing or seal failure 99% of the time they die.
I should have added that I do have a plow on the front of my truck so the air flow is restricted. How ever previous years same set up with no problems....
Ah ha.
Either your new radiator is defective (usually the culprit when something is getting hot under load, but will cool down when not under load) or you have a bad fan clutch. Your clutch may be slipping just enough to not pull enough air when you are going down the road under a load, and you are getting little to no help from incoming air since the plow is in the way.
Wait....it's winter time...... I say you have a stat not opening properly. It might be only partially opening. What I said above would more apply to warm weather.
Well, I just pulled the fan clutch, it is all soaked on the back side and on the thermo coil. When I took the belt off the fan blade would spin/free wheel with out any drag. I beleive the cluctch should cause drag and it should not spin to man revolutions. I think the cluck is bad?
what is the difference between standard rotation and reverse rotation? I am in the process of ordering one and I not sure what one to get. It appears the reverse rotation is only a few bucks more....
Someone can correct me if I'm wrong, but it might help you on your search.
Pretty sure reverse rotation is serpentine. Standard rotation is v-belt or ribbed belt that is not serpentine.(Edit: I see on your other thread you got this answer)
With a plow, the overheating makes a lot of sense as a fan clutch issue. Relying on the clutch working to move air due to the plow even at speed.
Make sure you get one that has the bimetallic coil. The cheap ones rely solely on the viscous fluid to lock them up, the bimetallic coil is a temperature control.
I hate to say it, as I dislike them, but if you run a plow all the time, a clutchless fan may be a cheap solution.
New fan clutch installed, will have to test to orrow when i can see to hook up plow. Old fan cluch was covered in oil including the bimetal temp coil. So hopefully this is the culperate
On a few of my plow trucks I had to "lock" the fan clutch in so it stayed engaged constantly,otherwise they would overheat driving more than 10 miles over 30 mph...once I locked in the clutch I could drive it anywhere,even at highway speeds..
The original fan clutch with the thermostatic spring on the radiator side can be "locked" by taking the tang on the spring off one of the holder/stop brackets and rotating it 180 degrees and clipping it back on the holder...a dealer service tech showed me that,he said they usually do this on any new factory equipped plow truck when they set one up...the fan will be noisier and may add drag to the engine and kill a few mpg,but its better than burning up the engine or blowing a head gasket,etc, from boiling over..
Its likely your clutch leaked enough of the silicone out of it to render it NFG,it wont drive the fan consistently enough at higher rpms without enough silicone inside it..
My diesel pickup never overheated with the plow on it (yet),the radiator is so huge even if the fan clutch wasn't up to snuff it wouldn't matter much unless I were driving long distances on the highway..
The v-belt water pumps are standard rotation,the serpentine ones are reverse,because they run off the flat or top side of the belt,which reverses the rotation...
The original fan clutch with the thermostatic spring on the radiator side can be "locked" by taking the tang on the spring off one of the holder/stop brackets and rotating it 180 degrees and clipping it back on the holder...a dealer service tech showed me that,he said they usually do this on any new factory equipped plow truck when they set one up...the fan will be noisier and may add drag to the engine and kill a few mpg,but its better than burning up the engine or blowing a head gasket,etc, from boiling over..
Its likely your clutch leaked enough of the silicone out of it to render it NFG,it wont drive the fan consistently enough at higher rpms without enough silicone inside it..
My diesel pickup never overheated with the plow on it (yet),the radiator is so huge even if the fan clutch wasn't up to snuff it wouldn't matter much unless I were driving long distances on the highway..
The v-belt water pumps are standard rotation,the serpentine ones are reverse,because they run off the flat or top side of the belt,which reverses the rotation...
Aaaaand there's the other change.
