Overheating after water pump replacement

[joshkbomb]

I put in a new water pump, lower radiator hose, and belts yesterday. Now the truck is overheating (at least according to the gauge). It's an '87 Blazer with a 350.

Things I've done so far or suspect:

1) I was having overheating issues this summer that were probably caused by an air bubble. So this time I went through the refilling process carefully and burped it a few times. Still overheating. I'm not 100% sure all the air is out, although I don't hear gurgling in the heater core anymore.

2) The thermostat is only 5 months old and was working fine before I did the water pump. I'm assuming it's okay.

3) I may have put the wrong rotation water pump on. I have V belts (with the one serpentine for the alternator) and assumed the standard clockwise rotation pump is the right one. I put in Napa PN# 43099p. Is there a good way to verify it's the right direction without taking everything apart again?

4) When the gauge is reading 260, the highest temp I'm getting with my infrared thermometer is next to the temperature sender on the side of the block at 235. Thermostat housing stays at 160-180, radiator and hoses about 100. This happened to me this summer too when I spent a few days diagnosing the gauge only to have air come out of the system and the gauge start reading normally. Very confusing.

 

[dyeager535]

Obviously you had problems with air in the systems, but I *thought* air pockets on these motors was not an issue...the radiator cap is the highest point in the system, air will find its way there, albeit eventually. Newer setups the cap is lower than other parts of the cooling system, which is why the motors have air bleeds on them. Anyways...

Any time I hear new waterpump + overheating I immediately think "wrong rotation". I run standard rotation, can't tell you how to tell if you got the wrong one or not.

If those temp readings are right, you have no coolant moving. Water pump or thermostat.

 

[joshkbomb]

After reading what I wrote, I realized I should just look at the old pump that's been on there for 6 years. Assuming the impeller "scoops" are moving to "scoop" the water, it is a counter-clockwise pump. I assume that the direction is measured from the front of the pump as if it was on the engine and you were standing in front of the truck?

Sounds like I have to take everything apart again. Geez.
Thanks for the sounding board!

 

[joshkbomb]

After reading what I wrote, I realized I should just look at the old pump that's been on there for 6 years. Assuming the impeller "scoops" are moving to "scoop" the water, it is a counter-clockwise pump. I assume that the direction is measured from the front of the pump as if it was on the engine and you were standing in front of the truck?

Sounds like I have to take everything apart again. Geez.
Thanks for the sounding board!

The plot thickens. According to this document from Napa, the impeller is supposed to push the water not scoop it. In that case, the old pump is clockwise.
https://partimages.genpt.com/partimages/1229847.pdf

Of course, I still have no idea what direction the pump I put on is. It says "standard", but who knows.

 

[K85 Octane]

if the fan is rotating the same direction as the crank, it standard rotation

opposite and it's reverse rotation
I've only seen reverse rotation pumps on full serp setups. Normally easy to spot because the crank pulley and water pump pulley will have different surfaces from each other (ex: cause the belt runs upside down on the pump, smooth VS. grooved)

When I checked the water neck temp on my other truck once, it came out to 10* more than what my stat was. Another truck I check was iffy, but it came to 200 and I think the stat was 195.

 

[K85 Octane]

also, check the casting number on the pump, then you'll see if it's right.




Really though, we need more info. When does it overheat, quick, slow, maybe, for sure.... That kind of stuff. Are you sure the lower radiator hose isn't collapsing once it gets hot? I can and has happened. Since stats are cheap, put a new one in.

Also, do you find yourself filling the bottle? Or spitting coolant out? With the engine HOT.......hours after letting it cool, is there pressure in the hoses? Oil and coolant both look good right?

 

[TheBeast_88K5]

Is yer radiator cap the right pressure rating?

My friends car over heated beacause the cap was the wrong pressure rating.
It backfed the overflow tank, which would cause it to lose fluid, trap air, etc.

Took him a while to figure it out.

 

[TheBeast_88K5]

After reading what I wrote, I realized I should just look at the old pump that's been on there for 6 years. Assuming the impeller "scoops" are moving to "scoop" the water, it is a counter-clockwise pump. I assume that the direction is measured from the front of the pump as if it was on the engine and you were standing in front of the truck?

Sounds like I have to take everything apart again. Geez.
Thanks for the sounding board!

Pressure is what moves the fluid, in the coolant system.
The water pump passively "assists" the coolant,
But is powered by the fluid that's under pressure.

 

[joshkbomb]

also, check the casting number on the pump, then you'll see if it's right.




Really though, we need more info. When does it overheat, quick, slow, maybe, for sure.... That kind of stuff. Are you sure the lower radiator hose isn't collapsing once it gets hot? I can and has happened. Since stats are cheap, put a new one in.

Also, do you find yourself filling the bottle? Or spitting coolant out? With the engine HOT.......hours after letting it cool, is there pressure in the hoses? Oil and coolant both look good right?

I can't see the casting numbers on the pump while it's on. Will they say which direction it is?

It idles slowly up to 260.

I replaced the lower radiator hose as part of the water pump install. I didn't see it collapsing when the engine was hot.

Filling the bottle as part of refilling the system? Not sure what you mean. Before the water pump went bad, I hadn't touched the coolant level in 5 months and it was still okay.

Not sure about the pressure in the hoses after cooling down.

Coolant and oil are fine.

 

[joshkbomb]

Is yer radiator cap the right pressure rating?

My friends car over heated beacause the cap was the wrong pressure rating.
It backfed the overflow tank, which would cause it to lose fluid, trap air, etc.

Took him a while to figure it out.

It's a 16 lbs cap.

 

[K85 Octane]

the pump wont say which direction, but you can type the number in to XYZ Auto store and check to see if it's right. Grab a flashlight and mirror, I can't remember where it's normally cast. Check the old one as they are normally in the same spot.

Filling the bottle after burping the system is fine, but down the road you might have a problem. My original motor was spitting coolant out of the reservoir and the hoses would stay hard days after running the engine. Problem: compression into the cooling system, causing overheating, and once the engine turned off, coolant leaks into the cylinder. Just a thought.

Did you ever replace the temp sender? Can you grab a hold of an aftermarket gauge and sending unit? Pull the old sender out and temporarily wire up the aftermarket one. Start and check. This way you rule out all those damn wires, connection, etc the stock system uses.

 

[K85 Octane]

oh, and for shiggles, bypass your heater core with a length of hose from your radiator to intake manifold. Again, just a thought if this doesn't end up being a wrong water pump. Normally though, I don't think a plugged heater core will hurt cooling capabilities

 

[Deuling]

You let it idle and heat up to 260*??. May just be me,but that sounds baaaad.

 

[joshkbomb]

I think I'm going to shoot my truck. It's toying with me. I went out this morning, noticed that the radiator was an inch low, filled it up, and it doesn't overheat idling in the garage like yesterday. So I drove it around for 20 minutes and the temp gauge never hits 210.

I have to be refilling and purging the air out of the system incorrectly. Is there a proper procedure for this? This is what I do:
1. Before starting the truck, fill the radiator up until the level stops dropping.
2. Start the truck with the cap off and make sure the radiator stays full.
3. When the water pump opens and starts to surge coolant out the radiator, rev the engine to 2500-3000 a couple times to get air pockets out.
4. Shut engine off and refill radiator.
5. Check coolant level in the radiator before starting until no filling is needed.

Can there be something wrong that causes air to get trapped and be a pain to come out?

 

[Deuling]

Ive always been told to turn the heat on. Not sure what it would do witg coolant flowing through the system though... And ive never done anything other than start it with cap off, watch it go down and keep adding coolant. Then once it starts bubbling up i put the cap back on and all is good. Alwaya worked fine for me. Sometimes a squeeze of the rad hose will burp some bubbles while its running with cap off, before it gets up to temp of course.

 

[dyeager535]

Fill the radiator up. Wait until the bubbles stop coming out, refill to top of fill neck. Fill overflowto "cold" mark. Start truck. Add coolant as needed to get it to the top of the fill neck. You can wait and see if it drops further if you like. Put cap on. Drive truck around, watch for temp increases, until it gets up to thermostat temp. Turn truck off. Let radiator get cold/cool (no pressure). Pop cap. If radiator is full still, check that overflow is at the cold mark, and you are done.

Turning the heater on is probably mentioned because some vehicles use a valve that shuts off flow to the heater core when anything other than "heat" is selected via the heater controls. I don't know as any of the '73-87 trucks used this valve, but I know some of the GM cars that vintage did.

Any trapped air should find it's way out through the cap, via the overflow tank, which is vented to atmosphere.

 

[Jessie James]

210 is normal operating temp. My 1991 Thermostat is 195, and that means it starts opening at 195.

When ever I hear water pump replacement and over heating I think about a problem I had once. Does your water pump have a nice cast impeller (right), or does it have a piece of metal that has bent "fingers" (left):

The one on the left is garbage. If that is what you put in, replace it. It just churns the water up and does not pump anything, which was my problem.

 

[Smokinthehippies]

Ive always been told to turn the heat on. Not sure what it would do witg coolant flowing through the system though... And ive never done anything other than start it with cap off, watch it go down and keep adding coolant. Then once it starts bubbling up i put the cap back on and all is good. Alwaya worked fine for me. Sometimes a squeeze of the rad hose will burp some bubbles while its running with cap off, before it gets up to temp of course.

It's bcuz the heater works by pulling heat from the coolant and blowing it out. What your hoping to do is rob some degrees from the coolant (lower temp) by blowing it as air into the cab.

The thing that jumps out to me here, is this problem is only while sitting and idling in a garage. How is the fan/shroud situation? Fan clutch? Cooling system can do no good if its only got stagnant air to breathe. Just a thought.

 

[454Sub]

Thats how I bleed my radiator of air, and I doubt I put that much thought into it. I fill it, start it, keep filling it until I get tired of it, put some coolant in the overflow, and drive and usually forget until I need to do something else, and its usually pretty close. Never had air bubble problems.

Your gauge could be off, my stock one reads about 20* hotter than when I put it on a scanner and read what the computer thinks it is. I have used a lazerbeam temp checker and verified that my computer sensor is reading correct, and my gauge is just off a bit. I have been meaning to put an elec Autometer one in as an extra gauge just to be sure.

 

[dyeager535]

The thing that jumps out to me here, is this problem is only while sitting and idling in a garage.

I had considered that too, but while unclear, my suspicion was he hasn't taken it on the road because he doesn't trust it.

You are correct though, if the problem goes away while cruising at steady speed, on flat ground, the problem is not the pump.