Guys,

I have replaced the waterpump, temp sensor (the one that drives the dash guage), the thermostat and flushed the whole thing such that I found clean fluid at the thermostat when I replaced it. I used a stock 195 degree thermo. Still, it is not opening and I am not getting flow through the radiator. Tried it with and w/o the cap installed. Guage on dash showed well over 200 degrees w/o and indication of flow through the top hose.

Truck is a '95 4x4 with 5.9. Ongoing project to help my son create his first truck. Thanks again for the help.

 

Did you test the t-stat before you installed it?

Hate to say it, but I would yank the t-stat and test it before moving on. Could have gotten a bad one.

 

Wrong water pump? Still got air in the system?

 

It is actually the second t-stat. The old one was only 2 yrs old, but the prob is the same. I checked the waterpump while the t-stat was off and it seemed to be pumping water when spun by hand. It fit perfectly with no issues on bolt holes or extra connections.

I am sure there is some air in the system, especially above the t-stat, but the fluid was right below it when I installed it. Would the air above cause a problem? That is why I tried it w/o the cap, to try to burp it. I can also tell you it has maybe half as much fluid as recommended, so there could be big air pockets in the engine. The radiator is full. The conundrum for me was the temp sensor, which is just to the left of the T-stat as you look from the front is registering the heat in the fluid right next to the t-stat at a temp that should open the t-stat.

 

In order to burp it you let it run while adding coolant and distilled water mixed around 50%. Turn the heater on so the t-stat will open and your entire cooling system is open including the heater core. It usually takes about 30-45 minutes for the cooling system to burp out the air. An incline helps a lot if you have a sloped driveway. Possible causes of an un-burped system include blown head gaskets so be careful and do not do a half-a$$ job!

 

THanks. I will try the burp tonight and see what happens. I did not have the heater on previously, so hopefully that does the trick.

 

Is the thermostat in the correct way?

 

Having the heat on or not makes no difference. Our trucks use a constant flow system, so, coolant is ALWAYS circulating thru the core when the engine is running. Turning on the blower just makes it take longer for the engine to warm up.

 

If you are right (HeyYou), then the burping has been attempted twice with no results. The T-stat is placed with the spring down. Went in good, seated flat and was careful not to get any sealer on it.

Does the sensor on the right side of the t-stat have any affect on things?

 

Yes, it can.
IIRC one of our members (VWandDodge had a similar problem for like a year, he replaced a temp sensor (can't remember which one) and it fixed it. You might PM him and ask him what he replaced.