So i have mentioned this problem before, but just getting back around to it...

I had an issue with my 99 Durango overheating whenever I would sit still idling for 20 minutes or so... And I was losing coolant from somewhere. I read here on the site about the Plenum Repair kit, and I was experiencing some of those symptoms as well, so I ordered the kit recommended on here, and did it. In the process, I found my coolant leak. It was coming from the tube that comes out of the top of the water pump (o-ring) and where the rubber hose clamps to the other side of the same tube. I believe that goes back to the heater core, but not sure.

So, I got that all back together, and replaced the thermostat with a 185 degree "failsafe to open" as recommended on here too. New t-stat, leaks fixed, I hoped for the best. But now it's worse. Now it will heat up just in normal driving, which it never did before...

I "burped" the system to the best of my ability.. I jacked up the right front side of the vehicle (where the radiator cap is), took the cap off, started it up, turned the heater on full blast, both front and rear fans on HIGH, and it eventually got up to around 190 or so, i think (gauge only has 210 and 260). I reved it up a few times and noticed that when I did, the coolant level would drop a little, then when I let off, it would come back up... Then some air bubbles would follow. Not sure if that was from air that came in when I reved it up (coolant dropped below top of radiator), or if it was from air that was trapped in the system.. Who knows?? Then I had a friend get in the car and hold it at 2,000 rpm's, the level dropped a little, I topped it of and quickly put the cap back on.

One of the things I read on here was that you can tell if the water pump is working by feeling the bottom hose. If it's hot, that's and indication the coolant is flowing, so the water pump is working. So, i got under there and grabbed the hose, and it was hot... That, along with the fact that the coolant level drops when I raise the rpm leads me to belive the water pump is working. I could be wrong... And I am not losing any coolant. The radiator cap is offset to the back a little, so you can't see across the fins inside the radiator to see the flow, but I believe I have enough proof that the water pump is good. Correct me if I am wrong... I also grabbed my fan, and turned it to see if it moves more than half of a turn, and it barely moves at all, so I assume the fan clutch is good too.

When I did the plenum repair, I also went ahead and replaced the distributor cap, rotor, plug wires and plugs.. All of the plugs looked good, clean, and even... There was no evidence of foul play in any of the cylinders. Aside from that, the vehicle runs great, and no smoke of any type. So I have no reason to suspect blown head gasket or anything of the sort.

If I can't get this figured out soon, I am going to have to sell it, and I don't want to because I really like it. Thanks in advance for any and all suggestions....

 

Yes the coolant level will drop when the RPM's increase. This is due to compression of the coolant. What you need to do is remove that T-stat sorry to say, they just aren't that good. Next I would go to a Auto Zone and buy one that has a little weap hole in it so air can get past it when filling. I think this one has one: Part Number: 15358
http://www.autozone.com/autozone/par...2_0_1632_93208

This is a 180 degree which will run the motor cooler, but more efficent. Test it in a pot of boiling water before installing it and make sure it opens. Don't alow it to sit on the bottom of the pan and ensure that it is fully submurged.

Next fill it with 50/50 and leave the cap off. Turn on the heater to high "HOT" as you did and full blast. Next start the truck and fill the level that has dropped. Next increase the RPM's just like you did to lower the coolant and while keeping it around 2000 RPM's top off the radiator and while still holding the throttle hury and place a new 16 lbs radiator cap on. I like Part Number: 7716 but each to their own.

http://www.autozone.com/autozone/par...42_167256_4559_


Next ensure that the over flow tube is not leaking or blocked and fill your reservior to the full line.

 

The thermostat I put in has the weep hole. I thought that was the "failsafe to open", but never-the-less, it does have the weep hole. At any rate, I will buy the one you said, and go from there. And I will get a new radiator cap too, even though I am fairly sure I replaced it already...

$20 or so will be well worth the peace of mind... Then we will go from there.

Thanks

 

Well, I personally have seen the "FailSafe" stick and therefore don't trust em. I have also seen others stick as well! That is why I say test em before install!

The rest of it, well you might not like a colder heater or a colder motor, but you will like the performance increase, the heads not wearing out, fuel mileage, and plain old better feeling hands down.