Truck overheating under load.

[hrcarver]

My old one ton(1989 chevy, gas 5.7L) is overheating(near the red on long hills) under load on a pretty regular basis. I do not recall it having this trouble before this year. Do water pumps go bad before leaking? Anything else it could be besides the thermostat?

 

[Thomas]

Maybe good rad. flushing plus outside rinsing also thermostat first.

 

[Diamondpilot]

As cheap as it is for your truck I would put a new water pump on it anyway. The real reason is your radiator. It needs professional acid cleaning or simply replace it. My dads Corvette was doing the same thing and I found a new old stock rad for $160 on the net.

Why I say to go ahead and replace the pump is you might as well while you have the Rad out. These old 5.7L motors are so cheap to work on. I would guess its less than $40.

So go shopping. Get a pump, T-stat, and a Rad.

Chris

 

[chips papaw]

well have you checked for any leaks.that would be the first thing.if you have to keep refilling rad its going somewhere pull the dip stick look for water in the oil this could be a sign of bad head gasket if not check the freeze out plugs they can look good on outside but they rust out from the inside they can just seep untill under pressure. if your truck has a lot of miles on it check raditor hoses they can cause same problem this truck should have a plastic jug for over flow from raditor they will crack on the bottom with age.heres something else if the truck has been driven a lot at night the cooling fins on raditor can be pluged up with dead bugs keeping it from running cool because the air flow is restricked.also check carpet under heater core see it it is wet that is a sign that a heater core could be leaking. these are things that can cause your problem that can be check without costing you money while trying to find the cause of your problem

 

[zzvyb6]

Do the easy things first. Pull the thermostat and see if the problem goes away. If there is a fan slip clutch, make sure its engaging when it warms up.

Look into the radiator opening and see if there is fluid flowing when the motor is running. Drain the radiator and see what comes out and how much. If you are loosing fluid, see if its a leak or its being burned. Look into the tailpipe and see if there is antifreeze residue at the end. Do you have a burp bottle? If it has a leak of its own, the fluid's just being pumped out. Fan belt tight? Manifold gasket any good?

 

[zene55]

Several things to check.

1. Level in the radiator before and after event
2. Fan belt - may be slipping - poor air circualtion and poor water circualtion
3. Water condition in radiator - if dirty flush it.
4. Oil in engine - does it have any water contiamination - may have head gasket leak.

 

[LD1]

I had a similar problem with my 03 chevy.

It was the fan clutch.

What type of fan do you have?? It could possibly be one of 3 types. Either a flex fan(fiberglass blades), it could be a rigid fan bolted directly to the pully with steel blades, or it could have the clutch. It is an aluminum looking housing that the fan bolts to and IT bolts to the pully. It's about 8" in diameter and has several "fins". This is the type I am talking about. If it is either a rigid or a flex fan, there isnt a lot to go wrong.

But the clutch fans are filled with a viscous fluid and they also have a bi-metallic spring. They are supposed to turn hard when cold, then get easier to turn, and then get more difficult as temps get even hotter. If one fails, the fan will still spin when the motor is running, just not as fast as it should. When you encounter an overheating event, pull over and shut the engine off and try to see how easy the fan will turn. If it has a decient amount of resistance, you are okay, but if it turns easy, it is probabally the problem.

Aside from that, if it is due for a usual service, it wouldn't hurt to change the coolant/flush the system, and maybe spend $5 and put a 160 degree t-stat in it. But chaning the pump and radiator and removing the t-stat ISNT going to help if the clutch is failing.

 

[LD1]

I just checked autozone and they do offer 3 fan clutches. A standard duty which is used without AC, A heavy duty which is used with AC and a higher rear end ratio, and a sever duty which is used with AC and lower rear end gears.


http://www.autozone.com/autozone/parts/1989-Chevrolet-K3500-1-ton-P-U-4WD/Fan-Clutch/_/N-ih5ohZ9pd92

So if your truck doesn't have AC and didn't come with the lower ratios in the rear, it probabally only has a standard duty chutch which wasn't meant for heavy towing. It may be worth upgrading to the sever duty clutch.

 

[SandburRanch]

My old one ton(1989 chevy, gas 5.7L) is overheating(near the red on long hills) under load on a pretty regular basis. I do not recall it having this trouble before this year. Do water pumps go bad before leaking? Anything else it could be besides the thermostat?

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Water pump impellers can wear to nearly nothing, but to check for pumping capability remove the heater hose supply and elevate it as high as possible. If water pumps out the pump isn't the problem. Replace the radiator or have it cleaned. Being a 89 don't be too surprised if the radiator shop says you need a new one because yours won't tolerate a cleaning.

 

[LD1]

I don't think a fan clutch would be much help. The fan itself is generally out of the cooling picture above about 35mph. The clutch type probably has more to do with fan size and number of blades. The fan could be 5, 6 or 7 bladed with different diameters. A 7 bladed 20" fan would put more of a load on the clutch than an 18" 5 bladed unit. The clutches also tend to disengage at around 2000 rpm of fan speed. While I'm on the subject of low speed cooling comments, the fan shroud is important too for low speed cooling.

I respectfully disagree.

While under normal circumstances this is general true, but under a heavy load, the fan is still able to deliver more airflow even at highway speeds, and still has a lot to do with helping the engine stay cool.

And regardless of what fan is on it, a heavier duty clutch can still be used. It will make the fan run more whereas a lighter duty clutch will let the fan start "slipping" at an earlier rate.

Or even better yet, if you can get a fan from an earlier motor that does NOT have the clutch, that would help out even more. The fan clutch came about to try to help improve economy by taking load off the motor when not needed. But I'd rather have a fan running all the time anyway. And in a 89 1-ton with a 5.7L, I doubt there would even be a noticable economy drop.