new water pump - overheating

[JohnnyC]

I first had the problem of coolant leaking so i replaced water pump with a re-manufactured water pump. I added a new coolant temp sensor (broke the old one) but used the same old thermostat. this has just been replaced recently and nothing was wrong with it. I installed everything correctly.

Now the car overheats. I have tried to bleed the system of air but i still dont know what the problem is. All the hoses get hot so i assume coolant is flowing. I did have some burping which was good, and i've bled from the valve on the thermostat housing.

I have also noticed the digital readout seems accurate, but the dash dial goes right to 260 and beyond. There is a big difference in readings. Dial is +40-50 degrees vs the digital readout. Shouldn't these numbers be the same?

Should i get a new thermostat? what are the chances the water pump is bad? Continue to bleed the system?

Could i have too much water in the 50/50 ratio? I have been adding alot, instead of dexcool.

Any help would be appreciated.
John -1996 LT4

 

[JohnnyC]

I've filled with coolant and water, removed the cap off the coolant reservoir and put a cleaned clear bottle upside down in(cut off the bottom too), ran the engine to 210 F and watched the coolant gurgle up in the bottle. Some bubbles came out. I then turned off the engine and let the coolant drain back down. Then ran the engine with cap back on 1 min. Then after cool, removed cap again and repeated. Done this a few times. I also bled from the bleed valve on the thermostat housing. On my last cycle, the coolant rose up into the bottle with no/little bubbling. and when i turned the engine off, the coolant drained down slowly.

I can still hear gurgling inside the reservoir as the temp goes to 230 F. I turn the engine off at this point.After turning off i can hear gurgling from the water pump.

If the head area is hotter, does that mean coolant/water is not in there yet (more bleeding)? or water pump not pumping water (bad water pump)?

 

[air1jpg]

Maybe unrelated, but make sure that little area between your radiator and condenser is free of derbies.

 

[LindenBob]

An old trick is to have the top radiator hose disconnected from the Tstat housing while filling. The majority of the air will escape and when you start seeing coolant come out reattach the hose and continue filling and bleed with your vents as you normally would. Also while you are running the motor and bleeding make sure your heater is turned on so it bleeds the heater core also.

 

[JohnnyC]

This is going to sound incredibly stupid, and a major rookie mistake!!! but after several attempts at trying to get the air out... and a new thermostat i knew there had to be something else wrong. I checked the service manual directions again... and i left out a MAJOR part. I did not transfer the coupling from the old water pump to the new water pump!!!!

Of course it was overheating!!! I am going to take everything apart when i get home from work today. Thanks for all the replies and i will update when i finish.

 

[JohnnyC]

All fixed and running fine in the 220's. Coolant is 50/50 mix. Digital gauge matches analog gauge. No leaks.

 

[LindenBob]

That was actually the first thing I though of but thought "Nah" :L
Happy to hear you are up n running

 

[WhalePirot]

All fixed and running fine in the 220's. Coolant is 50/50 mix. Digital gauge matches analog gauge. No leaks.

Gosh.. humility from a Corvette driver? Cool (oops); we learn from each other.

I suppose you think you're the first guy to do that?

 

[Brian Smith]

I did the very same thing about three weeks go. Exactly the same symptoms. Boy did I feel stupid! Thank the good lord a friend down the street who has a early 90s Camaro converted his to an electric water pump because in the two weeks I was trying to find out what had failed the core of the old water pump of course had been sent back. I bet the guy that unpacked that core figured somebody was having a very bad day.

Being an old troubleshooter of medical instrumentatation and systems I remembered that Sunday the I used to admonish the younger guys that "if you hear hoofbeats don't think of Zebras". When that came to me that Sunday morning I snatched the water pump off and was greatly embarrassed. This is after the guy with the spare coupler had told be I should have installed and electic water pump and I scoffed. Don't make it too hard and often the most obvious answer is the right answer.