Have you pressure tested the system?? Because a bad cap or the lower rad hose could be colapsing. Also is the cooling fan engaging??

 

Haven't pressure tested yet, on our second cap and the fan is engaging. But the hose collapsing thing, haven't thought of looking at that. It is like the driver side gets BOILING hot, then if you check the temp on the thermostadt housing, its like 60 degrees - then it pushes through. It is like there is an obstruction somewhere.

 

Sounds like you have a HUGE air pocket.. you need to bleed the air out of the system.... Which all you need to do is run the engine with the rad cap off...

 

If it isn't an air pocket, then you may have the wrong water pump. The introduction of serpentine fan belts reversed the direction that a water pump turns making it possible to have one designed to turn the other way.

All it takes is the parts person to grab the wrong one...

 

If it is the wrong water pump, I will just be ill. Wouldn't be the first time I have had the parts store mess something up! I will be trying to burp the sytem tonight and look at doing a pressure test. The last dealership mechanic I talked to said to cut out the center of the thermostadt, put it back in, and see where the obstruction was in the system. Makes sense, but if it is the water pump or a simple BIG air bubble, that won't help to elimate the thermostadt.

 

If it isn't an air pocket, then you may have the wrong water pump. The introduction of serpentine fan belts reversed the direction that a water pump turns making it possible to have one designed to turn the other way.

All it takes is the parts person to grab the wrong one...

I'll bet that's it Wis !! Doesn't have a reverse rotation w. pump on it!!

edit** Libby, if you cut a hole in the t. stat or take it out, it will appear to have fixed it because the coolant will circulate better, but won't cure it. Best thing to do right now is check the part number on your water pump reciept & see if it's the right pump. That is the easiest place to start.

 

do you have any squealing of your belts at all like a pulley locking up? my 1990 was doing something similar and it ended up being the bearings on my A/C compressor were out and locking up the belt. Do you smell any rubber burning? sounds more like a air pocket but these are easy to check as well

 

Nope, no squealing at all. I am just dying to check out that water pump part # now.

 

**Update*** truck has been burped, there was a couple bubbles that came out, checked the water pump, it is the correct one, checked the lower hose, it appears good, and WE ARE STILL HITTING 220 to pop the t-stat open. Ugg. Husband is now draining the system, pulling the water pump off, pulling the lower hose and checking to make sure there isn't any blockage in any of the lines and putting my old water pump back on to see if there is a difference.

 

may want to stick a new thermostad in there aswell.. and dont buy a cheap autopart store one, go to napa !!!

let us know what u find , hope u get it fixed !!!!

If not, please report back.

 

I have been learning about cooling systems recently, and a couple of questions come to mind for me... have you tested your coolant temp sensor and coolant temp sender as well? Also, have you tried a 180 degree t-stat instead of a 192 degree t-stat?

One more thing... have you tested t-stat? It's easy. I use a pyrex glass of water and a thermometer (the kind used in coffee shops). Microwave water then insert thermometer to check temp of water, and drop t-stat in water to see if valve opens normally, then closes normally as water cools off.

 

Well, we did a different t-stadt a 180 degree one, and one with out the round foot feet at the bottom of it. Now, the truck runs at a balmy 195. Still bobbles between 150 and 195, but not like it had been. In response to the other post, yes we changed the sensor and the sender. The 4 t-stadts I had gotten were 2 from Advanced Auto, 1 from Napa, and 1 from Carquest. Amazing to think they all may have been bad. Very very strange. We will see if this is the ultimate cure!!!!

 

Glad the lower degree t-stat is helping. I would still test the sensor, as I believe the sensor may be causing the bobbling gauge. It's similar to testing the t-stat. Place end in water. Use thermometer to check temp and ohmmeter to check resistance. Should get a certain resistance based on the water temp.

I've bought new parts from the local store that have been defective. Always good to test before installing, especially when it is a pain to get to if not working properly.

 

I'm still betting it's something else. I've never gotten 4 bad thermostats in a row. Never even had 4 bad ones out of 20, so the odds are the problems somewhere else.

 

I'm still betting it's something else. I've never gotten 4 bad thermostats in a row. Never even had 4 bad ones out of 20, so the odds are the problems somewhere else.

I agree, the lower temp just means the coolant is starting to circulate quicker. Since it never rose above 220 [which isn't too high as antifreeze raises the boiling point] the problem may be small...for now!

 

I agree, the lower temp just means the coolant is starting to circulate quicker. Since it never rose above 220 [which isn't too high as antifreeze raises the boiling point] the problem may be small...for now!

I agree, but man ..my truck never sees over 140 !!!! and its a stock thermostat !!

and bubling between 150ish.. I think u have air in the system somewhere !!

 

220 degrees is not necessiarily worrysome. 15 lbs of pressure on the system and a 50-50 antifreeze mix translates to almost 250 degrees before boil. in the 70's there were GM vehicle's that used a 215 thermostat. They did not have a temp gauge on them, because of the reaction you are having, and the red temp light was set at 245.

 

Reading this thread, I didn't see any crazy high temps, granted it should be lower, but we're talking about a 1997 vehicle. Has a flush been done of the cooling system, I didn't read if a pressure test had been done or not either.

 

The bobbling of the gauge seems to have subsided, and the t-stat opens right at 210 and goes down to about the 140 range. Husband did a pressure test and I cannot remember what the official results were, but he said it was good. I think my gas mileage has gone down too now. We had the system flushed when we got the truck so about a year ago.

 

140* is too cold. Could explain the poor fuel mileage. It really should have the 195* stat in it...