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need a new thermostat or water pump
i have an 89 gmc r3500 with a 454 and it overheated on my drive and could only drive a few miles before you had to let it cool off some.so i ended up removing the thermostat and it made it the final 5 to 7 miles back home without overheating.i looked into the radiator and you can see water coming from the driver side of the rad flowing into the passenger side with the thermostat out does that mean the pump is ok?
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If your truck did not over heat with the thermo out then it's the thermo. If it did over heat with it out then its the pump.
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Originally Posted by Seanjordan20
(Post 1627744)
If your truck did not over heat with the thermo out then it's the thermo. If it did over heat with it out then its the pump.
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Originally Posted by Seanjordan20
(Post 1627744)
If your truck did not over heat with the thermo out then it's the thermo. If it did over heat with it out then its the pump.
Originally Posted by wes104
(Post 1627746)
ok so since it didnt overheat any more in that 5 to 7 mile drive with it out it more then likely the thermostat.
Water pump pumps coolant to take excess heat from the engine and deliver to the radiator. The radiator transfers a bunch of that heat to the air. The thermostat restricts flow of coolant to keep the engine at an efficient operating temperature for power, emissions, efficiency, metallurgy-concerns, HVAC heat stability, etc. When it works correctly it opens at the specified temperature to allow the coolant that is warm in the engine to move to the radiator. Sometimes, however, a thermostat will get stuck closed. That appears to be the problem you had before removing it. |
What if an air pocket was created by a coolant leak?
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Originally Posted by Tech II
(Post 1627756)
What if an air pocket was created by a coolant leak?
Good point. For it to start that quickly it would probably have needed to be at least a small puddle on the ground where it was parked before he drove it this time. If he missed the puddle and/or it was parked on dirt/gravel/etc. then removing the thermostat allowed the air pocket to move to the radiator and hopefully to the overflow tank. If that happened then putting in the new thermostat won't fix the leak (unless it was leaking at the thermostat housing). wes104 , after you install the new thermostat, keep an eye on coolant level and look for leaks. |
Originally Posted by CathedralCub
(Post 1627783)
Hmmmmmmm . . .
Good point. For it to start that quickly it would probably have needed to be at least a small puddle on the ground where it was parked before he drove it this time. If he missed the puddle and/or it was parked on dirt/gravel/etc. then removing the thermostat allowed the air pocket to move to the radiator and hopefully to the overflow tank. If that happened then putting in the new thermostat won't fix the leak (unless it was leaking at the thermostat housing). wes104 , after you install the new thermostat, keep an eye on coolant level and look for leaks. |
Originally Posted by CathedralCub
(Post 1627783)
Hmmmmmmm . . .
Good point. For it to start that quickly it would probably have needed to be at least a small puddle on the ground where it was parked before he drove it this time. If he missed the puddle and/or it was parked on dirt/gravel/etc. then removing the thermostat allowed the air pocket to move to the radiator and hopefully to the overflow tank. If that happened then putting in the new thermostat won't fix the leak (unless it was leaking at the thermostat housing). wes104 , after you install the new thermostat, keep an eye on coolant level and look for leaks. |
if it was the water pump or a air pocket it would be all the time wouldnt it not just sometimes
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Originally Posted by wes104
(Post 1627798)
see it might help some if i explain some.when i took the trip i drove to the town thats about 20 miles away and it didnt overheat on the drive there but it did on the way back.i was about 5 miles away from home so i just took the thermostat out and it made it home without a problem.also i dont know if it matters but the top radiator hose had alot of pressure on it and when it overheated the radiator cap let out some water.thanks for all the help so far.
A couple of questions I've been waiting to ask: How old are the thermostat, hoses, and cap? |
Originally Posted by CathedralCub
(Post 1627811)
Yeah the whole system should be at the pressure rating of the cap. After warmed up and on a warm day the hose should feel like my kid's bike tire or thereabouts.
A couple of questions I've been waiting to ask: How old are the thermostat, hoses, and cap? |
can the bad cap be causing it to build up to much pressure or something
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Originally Posted by wes104
(Post 1627813)
can the bad cap be causing it to build up to much pressure or something
Lay it on its back on a sturdy surface. your goal is to press on the rubber part of the plunger, not the center. It should compress with a smooth action if you put around ten pounds of pressure on it with your thumb. it doesn't need to go far, just a quarter inch or so. |
Originally Posted by wes104
(Post 1627814)
https://cimg4.ibsrv.net/gimg/www.gmf...ffe869b6bf.jpg
https://cimg7.ibsrv.net/gimg/www.gmf...069f56cfa0.jpg |
Originally Posted by CathedralCub
(Post 1627816)
Pretty rusty. Looks like you're due for a flush anyways. For what it's worth, that isn't the original GM cap. It looks like a Stant possibly.
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if i take the thermo out and take the top radiator hose off the rad and start it for a sec would that show if my water pump is working fine
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If you take the thermo out and you run the car and it does not over heat that tells you that your pump is working. You've done that when you drove the 5 miles.
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Does it overheat just as much at 5AM as at 3PM?
How is your fan clutch doing? Can it sit and idle indefinitely without overheating? If the fan clutch is not doing its job and the weather is really hot out then you will definitely overheat, even without pulling a load. Also if it is a standard-duty fan clutch and you rev more than around 2,000RPM engine speed while driving at highway speeds, it will freewheel. A severe-duty fan clutch will bring the fan to ~1,800RPM fan speed (or lower if the engine is spinning slower) no matter the engine speed. If you're buzzing along at 2,500 or 3,000RPM engine speed and the fan clutch is freewheeling for your aural comfort then the engine will run hot.
Originally Posted by wes104
(Post 1627817)
i think ive narrowed it down to the cap
Originally Posted by wes104
(Post 1627817)
or the radiator
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Originally Posted by wes104
(Post 1627818)
if i take the thermo out and take the top radiator hose off the rad and start it for a sec would that show if my water pump is working fine
Originally Posted by Seanjordan20
(Post 1627819)
If you take the thermo out and you run the car and it does not over heat that tells you that your pump is working. You've done that when you drove the 5 miles.
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Originally Posted by CathedralCub
(Post 1627844)
Agree.
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Originally Posted by CathedralCub
(Post 1627843)
Does it overheat just as much at 5AM as at 3PM?
How is your fan clutch doing? Can it sit and idle indefinitely without overheating? If the fan clutch is not doing its job and the weather is really hot out then you will definitely overheat, even without pulling a load. Also if it is a standard-duty fan clutch and you rev more than around 2,000RPM engine speed while driving at highway speeds, it will freewheel. A severe-duty fan clutch will bring the fan to ~1,800RPM fan speed (or lower if the engine is spinning slower) no matter the engine speed. If you're buzzing along at 2,500 or 3,000RPM engine speed and the fan clutch is freewheeling for your aural comfort then the engine will run hot. The cap doesn't control coolant flow through the system. You should be able to keep the engine cool with no cap at all if the coolant magically stayed in somehow. If the cap is allowing too much pressure to build, your engine would still run cool until a gasket/seam/hose/etc. gives out and dumps your coolant on the ground. It might be that the radiator is plugged up a lot. With the way the cap looked, odds are good. I'd suggest: with engine cold, open radiator cap and look inside. Hopefully you are a couple of inches low on coolant (but not much more than that). If not, siphon some out or use a turkey baster to get it a couple of inches low so you can see the tubes. Put the excess coolant in the overflow tank or an empty coolant bottle. Start the engine and monitor the upper hose temperature by occasionally holding your hand on it while also looking into the radiator. When the engine gets warm enough, the thermostat will allow coolant to flow to and through the radiator. When it does, coolant coming out of the tubes should be just dribbling. If they are squirting like miniature garden hoses with miniature thumbs on them then odds are good the radiator is plugged. If there is no flow at all, then it is plugged in the top tubes. |
Originally Posted by CathedralCub
(Post 1627844)
Agree.
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Do you know how a fan clutch works?
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Originally Posted by wes104
(Post 1627853)
i know it probably dont mean anything but i took the belts off and gave the water pump a spin and theres no resistance.should there be some from the water that in there
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Originally Posted by wes104
(Post 1627852)
i know the fan cluch is probably oringinal to the truck.
Come to think of it, I don't think I've never seen a 30/35/350/3500-series truck that is more than five years old that has less than 10,000 miles on it.
Originally Posted by wes104
(Post 1627852)
when you rev the truck it speeds up but not by much
It operates more like a torque converter, like when it is engaged it does what it can through manipulating fluid (inside the clutch) to get the fan to spin up to 1,800-2,000RPM. That makes for smooth engagement and disengagement, less noise, less belt stress and wear, longer water-pump bearing life, and less life and property damage from chunks of fan flying off. When you rev it, you'd have to rev it to 2000RPM+ and keep it there for a couple of seconds to hear if the fan is doing anything, and even then it would only do what it is supposed to if the coolant temperature is high enough. Just had a thought: Long ago there was a cheap alternative to a thermostatically-controlled fan clutch. It was a non-thermostatically-controlled fan clutch. I think they operate as always-on (as in my second example above) regardless of temperature while saving you a few bucks at time of purchase. I've never used one because they are dumb. I don't know if they still sell these, I just know I haven't been asked if I want the thermostatically-controlled option or not in the last decade. You might have one that's all worn out (and still dumb) in your truck. Maybe it was installed in 1994 when the factory fan clutch failed (or something) and it just looks old enough to be original. Either way, it sounds like you need a fan clutch. |
Originally Posted by CathedralCub
(Post 1627909)
I've never seen a traditional fan clutch last 29 years and still work. Especially on a truck. Especially on a 30/35/350/3500-series truck. Unless it was almost never driven and is still working on rolling that fifth digit on the odometer. Seems like replacing the fan clutch with a severe duty one (while you're there) would be a good idea.
Come to think of it, I don't think I've never seen a 30/35/350/3500-series truck that is more than five years old that has less than 10,000 miles on it. It doesn't operate as a clutch, like when it is engaged the fan is locked to the shaft. If it did, your truck would sound like an Indy car whenever it revved above 2,500 or so, right up until a chunk of blade came shooting out your hood and impales your neighbor's cat. It operates more like a torque converter, like when it is engaged it does what it can through manipulating fluid (inside the clutch) to get the fan to spin up to 1,800-2,000RPM. That makes for smooth engagement and disengagement, less noise, less belt stress and wear, longer water-pump bearing life, and less life and property damage from chunks of fan flying off. When you rev it, you'd have to rev it to 2000RPM+ and keep it there for a couple of seconds to hear if the fan is doing anything, and even then it would only do what it is supposed to if the coolant temperature is high enough. Just had a thought: Long ago there was a cheap alternative to a thermostatically-controlled fan clutch. It was a non-thermostatically-controlled fan clutch. I think they operate as always-on (as in my second example above) regardless of temperature while saving you a few bucks at time of purchase. I've never used one because they are dumb. I don't know if they still sell these, I just know I haven't been asked if I want the thermostatically-controlled option or not in the last decade. You might have one that's all worn out (and still dumb) in your truck. Maybe it was installed in 1994 when the factory fan clutch failed (or something) and it just looks old enough to be original. Either way, it sounds like you need a fan clutch. |
Originally Posted by wes104
(Post 1627910)
i was looking into a fan cluch and they say clockwise or reverse clockwise witch should i get or whats the best way to tell.if you stand it front of the truck the fan spins clockwise if that helps
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Originally Posted by CathedralCub
(Post 1627941)
It's clock/counter based on staring at the car from the front as if it is about to run you over. Generally if it has V-belts it's clockwise and if it is the smooth (non-grooved) side of a serpentine belt then it is counterclockwise. If it has a serpentine with both sides grooved then it probably doesn't have a fan clutch anyways, but at least if it does you can still tell by standing in front of the car as if it is about to run you over and deciding clockwise or counterclockwise.
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Originally Posted by wes104
(Post 1627945)
it actually has both v belts and a serpentine belt.i was looking at the water pump and it is a clockwise one and since there bolt up together that should mean the cluch is clockwise to right
Either way, if the fan/water pump spin the same way as the crankshaft then it is clockwise. |
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