Possible overheating issue

[Burbdood 74]

Got a problem here....

I swapped out my leaking water pump for a new Napa one, (part # TFW 43099) and now the temp guage is bouncing all over the place. I can drive across town and the guage climbs and climbs up to 200*, but it will climb up to 260* occasionally while I'm driving along. I can stop at a light and it will come down to 200* again, but then while driving, it will climb back up to 260* and then fall again to 220* or lower and then start climbing. Like I said, the guage just bounces around. I looked inside the radiator with the truck running and coolant is moving really well too.

The bottom hose is warm-ish, but the top radiator hose is much hotter to the touch and seems to have a kink in it, but nothing is hot enough to scald you. I should add that both hoses and thermostat are 2 years old. It's also not puking out any of the coolant into the overflow tank.

So, do I have air trapped in the system like I suspect or do I have a bigger issue going on? Thanks in advance...

 

[snowdriver]

i think maybe you did not get the correct water pump,you should have a reverse rotation one on there,i think,i am assuming you have a serpentine belt with a/c and power steering

 

[ktmoutfront]

If the bottom hose is cooler than he top, rotation should be ok. I've seen thermostats cause that. If coolant is moving from the top hose with the cap off, I would say no to trapped air. Not really a place to get trapped in these trucks.

Why was the pump changed?

 

[Burbdood 74]

The pump was changed because the old one was leaking out the weep hole. As far as a serpentine belt, that's a no. 1988 was, I think, the last year for the V-belt before GM switched to the full serpentine. It has a serpentine type belt for the alternator/water pump, but the new pump is identical to the old one.

My thought is if it were truly overheating, the guage wouldn't bounce around, the heater would be blowing out scalding hot air, I wouldn't be able to leave my hand on the top hose for longer than .2 seconds and it would be puking coolant into the overflow bottle.

Am I assuming correctly or just spitting in the wind?

 

[ktmoutfront]

You may have a sending unit or gauge issue. I bought a cheap temp gun a while back when my daughters car was having heating issues. Point it at the engine output hose and instantly new it was electronic. Sending unit was bad.

Depending on how full the system is, at 260 it may not push coolant into the over flow tank.

 

[Burbdood 74]

It's just weird that it would do this after I change the water pump and never before. I hope to hell that Napa didn't sell me a defective pump.

I'm also wondering if my radiator cap is bad.

 

[ktmoutfront]

Does it get hot only when you are driving at 1500 rpm's or more for extended periods? Then cools when you stop or at least run low rpm's?

 

[Burbdood 74]

The gauge bounces around while driving or sitting, doesn't seem to matter. I can drive it nice and calm and it's hot, come to a stop, temp comes down. The next light, it's hot and stays there and comes down as I take off from the red. There doesn't seem to be any rhyme or reason for this and that's what's weird.

 

[rampage]

How's the condition of the belt on the pump? Maybe it's slipping.

 

[Burbdood 74]

The belt is great, no slipping at all.

 

[chulisohombre]

Sounds like a sending unit problem or Guage. The sending unit is grounded to the block and sends a negative signal as the truck heats up and resistance changes the elictric signal to the Guage. When I had a bad ground to my Guage cluster I was getting weird signals and the guages would change with brake and tail light pulses and with turn signals. Check the connection at the temp sender when cold and when it's at normal temp and at idle it should not jump like you are saying. If it does then you may have found your problem. It sounds like the radiator is moving the coolant fine and the thermostat is opening correctly. Stock cap is a 16 psi and they do wear out over time. Also make sure the rad is full of coolant and no bubbles.

 

[Burbdood 74]

Sounds like a sending unit problem or Guage. The sending unit is grounded to the block and sends a negative signal as the truck heats up and resistance changes the elictric signal to the Guage. When I had a bad ground to my Guage cluster I was getting weird signals and the guages would change with brake and tail light pulses and with turn signals. Check the connection at the temp sender when cold and when it's at normal temp and at idle it should not jump like you are saying. If it does then you may have found your problem. It sounds like the radiator is moving the coolant fine and the thermostat is opening correctly. Stock cap is a 16 psi and they do wear out over time. Also make sure the rad is full of coolant and no bubbles.

At this point, I have to agree with this. I drove around for about an hour this morning with my girls running errands and the gauge was bouncing all over the place, but not once did it smell hot or boil over and I was able to take the radiator cap off while it was hot and it didn't try to blow out any antifreeze on me. Time to check the true temp with a thermometer and possibly time for an Autometer temp gauge.

 

[Burbdood 74]

Thought I'd put a (hopeful) end to this...

So I swapped out my gauge sending unit and the temp gauge still moved around. I replaced the thermostat and it still moved. I just finished replacing the water pump an hour ago.

Anyhoo, after filling up the system, I drove it around some and the gauge got up to 215* and came down to 210* a couple of times but it never even got close to 230* or above. I'm thinking when I top off the coolant, it should be pretty close to normal again. As it stands now, it looks as if Napa sold me a bad water pump.....I hope.