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Discussion Starter #1
Purchased a 2005 dakota SLT 4.7L Magnum with 78k on it in jan. after a couple weeks there was a knocking in the motor which the dealer said was a stuck lifter that did no other damage, they fixed it. After that I noticed a significant coolant loss but no spots in the driveway. They said it was the water pump and changed it but still the same coolant loss. Brought it back and they did a compression test, o2 test, pressure test, checked for leaks, freeze plug, and replaced some hoses and the radiator cap. There was no signs of coolant in the oil and some milky residue under the fill cap that I wiped off a month ago and it hasn't been back. No one can find the problem. They then put die in the cooling system so they could find the leak with a uv light they then drove it 200 miles and gave it back saying the level hadn't gone down and marked it for me. After 200 miles I checked it and it was down 3 inches. I did notice a little coolant in the snow after an hour long drive but am not sure if it was from me or another car. I again brought it back after racking up some more miles to try and bring it in while leaking. We both looked under it and everything was dry and the level was back up but still an inch lower than the original line. What are some other things this can be? It doesn't seem normal for the res to fluctuate that much between warm and cold. Should I take it to another shop to try some other tests?
 

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The Anti-RUB
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The level in the reservoir will fluctuate a lot between warm & cold. It will go down when cold, and up when warm.

The compression test they did is not a conclusive test. It is trying to see if there is a head gasket leak dumping coolant into the cylinders and boiling it off & out into the exhaust. Sometimes small head gasket leaks don’t start leaking until the motor is hot (metal expands when hot making the crack bigger). I’d rerun the radiator pressure test & compression test with the motor warm.

Good luck...
 

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Discussion Starter #3
thanks for the reply. the compression tests and pressure tests were done when warm, or so he says. though the levels will fluctuate a lot when hot and cold, i have added over a gallon to the cooling system so i know it is going somewhere, and when it goes down then comes back up, it never makes it way back up to the previous line, it just slowly works its way down lower and lower.
 

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The Anti-RUB
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Did you ever poke around your motor with a black-light looking for the coolant dye that the shop put in? In a dark location shine a black light all over the place. Above, below, front, back, side to side... You can pick up a small black-light flash light from various stores for pretty cheap.

In addition I’d rent a radiator pressure tester from your local auto parts store, hook it up in place of the radiator cap, pump it up to the same PSI as on the radiator cap, and then wait, look & listen. The PSI should hold for about 15 minutes. If not, then you have a leak. If you have a leak, and there isn’t a lot of background noise, you can sometimes hear a hisssssing sound of the coolant leaking. You’ll also see it dripping on the ground. Shouldn’t be too hard to track down. Good luck...
 

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the dealer said they have checked with the lights and the pressure test all checked out. they have it now and i should be getting it back tomorrow, its been months and they cant figure it out so i am bringing it to a friends shop to have him check it out before trying to get my money back for the truck
 

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A cylinder leak down test could help determine if that's the cause. It's different then a compression test in that it is designed to hold pressure in the cylinder to see if it bleeds off and how fast. Do it with the engine cold first thing in the morning and then do it again immediately after a 20-30 minute test drive. One or two cylinders should leak more than the others but it may be slight. If its 5-10psi that's a good indication that there is a tear in the head gasket and its ready to blow.

You can also do a cooling system pressure test. Do it hot and cold but go to 1-2psi above the cap. This will force the coolant to the leak. If it starts to go down but you can't find it then continue pumping it up and looking for it. After a short while have someone watch the tailpipe and start the truck. If there's more than a couple tablespoons of water come out then that's a good indication of a leaking head gasket.
 

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Another possible issue could be..... You say the leak formed AFTER they replaced a lifter???

I believe that 2 or 4 intake manifold bolts go into cooling passages and you must put rtv sealant on the threads of the bolts to seal it. If not then it will allow a slight amount of coolant to be drawn into the cylinder and burned off.
 

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Discussion Starter #10
Yes it has been checked. It has now slowed its leak and isn't dropping as fast at all but km going To keep monitoring it and over the next few weeks ill pull the head when it starts going quicker
 
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