what am I doing wrong?

[deadeye]

My Dad has got a 03 Durango with a 4.7.

Recently the thermostat went out. I changed it, no problems and confirmed that it was bad with the old pot of boiling water. Three weeks go by, no problems.

He calls me friday telling me that its overheating again. So he gets it home and as I suspected it had burped a big air bubble. I fill it up again and drive it around with no issues. I had also picked up a pressure tester in the mean time and could not get any weird readings running or not. No leaks no spikes in pressure like its got a bad head gasket. It just ran steady at 20psi (what the radiator cap is rated at).

I just happened to have tires put on it and had it aligned Saturday as it was rolling on bald tires. The shop had test driven it for the alignment and it didn't act up for them. It was also just fine too and from the shop for me.

I shouldn't have done it but I decided that I was gonna plop another t-stat in there for the piece of mind. Well I guess that was a mistake. It cant make it around the block without it heating up.

Last night I would run it till it got warm. Let it cool down, add coolant and repeat. I did that about 5 times.

I just got through letting it set for a 45 minutes with one of those no spill funnels attached and it did burp up quite a bit of air. Still gets hot on a short drive though.

While its hot it does seem to help to have the heat running. If its setting still the temp will go down to the normal level and stay there.

I had also replaced the fan clutch as it was pretty bad too. It had quite a bit of play and it was spinning slow while the engine was running hot.

Am I just going to have to be patient with it and assume its got a huge air pocket? It there a better way to get air out or should I be looking to something else?

I have never had so much trouble with a cooling system and its starting to get to me if I'm honest. Im really kicking myself for putting the second stat it. If it was my own truck I wouldn't be too concerned but its my dads truck and I want to get him going.

[Jeremy airjer W]

With the no spill funnel attached and the vehicle hot do you see a steady stream of air bubbles percolate out of the funnel? If its consantly burping air but the coolant level in the no spill never goes down than you probably have head gaskets failing.

[deadeye]

Well my dad ran it for a bit today with the no-spill on it and he said there was lots of bubbles the size of a large marble popping up.

[Jeremy airjer W]

Doesn't sound good.

[deadeye]

Now I'm at home and there is pretty much minimal bubbles coming out. A random one here and there but not a steady stream.

I forgot to mention that there was no heat in the rear.

I'm thinking about taking it and finding a steep hill and letting it idle with the nose up hill.

What's really got me miffed is that Saturday it didn't act up at all before I put the new stat in. It acted just as it would any other time.

I guess I don't got a huge problem doing the hg's but I just want to know that they are what's wrong. Still no odd readings on the pressure tester either. No chocolate milk oil. Nothing floating in the coolant. I am thinking about getting a vapor tester and trying that.

[waterfowler10]

If you haven't tryed this wash the cap in warm soapy water or buy a new one there pretty cheap sometimes the caps fail and won't release the right amount of pressure if any at all hope this helps

[Jeremy airjer W]

Revving the engine in short bursts will work out any air in the rear heater core.

[jeffreyd]

if you have a pressure tester and adaptor you can check the cap, however if you have not replaced it, i would do that next, it might be opening enough to not build pressure. have you replaced the hoses, are the closing down starving the engine for cool water? i do mine every 5 yrs or so, just cause they break down over time.

[deadeye]

New radiator cap and the hoses are in decent shape and only a year old. They are the ones with the coil spring on the inside so they don't really close up but I can watch them and don't see anything happening out of the ordinary.

I am going to see if I can get my hands on one of those vapor testers and give that a shot. I don't understand how it could have a bad HG but not make the pressure tester do anything weird, make the oil milky, loose coolant, or have coolant in the oil. Its driving me nuts. I suppose its my luck for weird stuff though. Just got to roll with it. I suppose its another good story to tell when I get it figured out.

[deadeye]

So I gutted the thermostat and it doesn't go above the cool mark....?

Am I having bad luck with t-stats or am I loosing it.

[Jeremy airjer W]

I don't understand how it could have a bad HG but not make the pressure tester do anything weird, make the oil milky, loose coolant, or have coolant in the oil.

If (we still don't know for sure as you may be dealing with burping the air out) the head gasket fails between the cooling jacket and the cylinder you will never see coolant in the oil, oil in the coolant, or notice a coolant leak. The hydrocarbons (bubbles) get into the coolant during the compression/power stroke. The 16 psi of coolant pressure may not be enough to get into the cylinder but a 100 psi and well over is enough for hydrocarbons to push there way into the coolant.

When the t-stat went bad did the vehicle over heat or did it never get up to operating temp?

[deadeye]

It got hot but from what my dad says he got it over and cooled down before it pegged. I'm pretty cautious so when I test drove it I didn't let it get too hot. I know that if you keep letting it get hot or get it very hot once you can blow the gaskets out or even warp the heads in some cases.

Should I do a compression test then? Would it show up with that? I got a decent tester so tommorow I will give that a shot just for piece of mind. Should I pull the fuel pump relay to stop the fuel or just pull the injector connectors?

Oh yeah, the reving trick did work pretty good. Lots of air came out when I did that. I am swapping that stat out tommorow Eve with a mopar part. I am sick of getting junk from the parts store.

[Jeremy airjer W]

The only thing that will tell you if there is a problem in the beginning stages of a failure is a four gas analyzer or on experienced nose!

Otherwise go with the O.E. t-stat. Fill up the radiator. Let the vehicle come up to temp at idle (no revving). After the t-stat opens continue to top off the radiator as necessary and give it short burst of throttle every once and a while. Once the bubbles have slowed down you should be able to bring the RPM's up off idle and hold them and watch more bubbles come out as the t-stat cycles. Continue until there are little to no bubbles and cap it off.

[Valv]

I don't have a gas 4.7 but maybe being a Dodge the system works similar to their diesel trucks.

To correctly remove any air bubble the procedure for Dodge Cummins trucks is to fill the radiator completely and the reservoir bottle to the MAX or HOT level. Run motor to regular temperature, be sure your temperature knob on dash and rear heat are set to hot. DO NOT open radiator cap or let it idle with cap off. Shut engine down, fill the reservoir bottle to the HOT level again. Restart engine and run truck again. Continue filling the reservoir bottle ONLY to the HOT or MAX level.

That's it. The secret is not to open the radiator cap while running motor, just add from the reservoir bottle.

I hope this maybe helps.

[Surface Tension]

My 3.0 Villager was a bugger to to bleed the air out of the system.

Remove the radiator cap and put a shim under the seal(a heavy wire bent in a C) that allows the air out of the radiator and travel into the reservoir. It took a very long time at high idle(3000 rpms)to completely bleed out the air.

[Jeremy airjer W]

My 3.0 Villager was a bugger to to bleed the air out of the system.

I'm sorry you had to own that!

[Surface Tension]

Its got around 280,000 miles.

Runs and drives mint.

Fact is with all the new parts its almost new.

[Scott K]

Originally Posted By: Surface Tension

My 3.0 Villager was a bugger to to bleed the air out of the system.

I'm sorry you had to own that!

[katophil]

I've seen those housing warp, and leak or suck air. RTV around the edge may solve it for you.

[deadeye]

I put the mopar tstat in it when I got home tonight and its mint. I beat the pi$$ out of it and she stayed just under the middle mark the whole time.

Officially I am done buying murray products from oreillys, especially when the mopar part was actually 8$ less. I. Am getting my money back tommorow for the one I hacked apart last night.

Thank you guys for the help. I think its my luck with stuff so I have gotten used to it but I think it helps having a braintrust to ask.