I have a coolant leak on a 2000 Dodge Dakota 3.9L 4x4. Coolant is dripping from the area where the bell housing meets the transmission. I can eliminate several locations the leak may be coming from, but I haven't been able to stop it.

• It's not the freeze plugs because I removed the transmission and inspected each of the freeze plugs. I did have one freeze plug on the side of the engine (next to/behind the starter) that was corroded and leaking and it has been replaced, but this did not totally solve my coolant leak issue.
• I do not think it is the heater core because all of the hoses going into the cab look great and there is not evidence of leaks on these components.
• It's not coming from the front of the engine (water pump, thermostat, bypass hose); I replaced several gaskets/hoses/clamps there and am not seeing any trace of a leak at these locations.
• I should mention that I do not have loss of power, nor is my oil showing milky/contaminated, so I do not think the heads are leaking or coolant is getting into the oil. The coolant is simply dripping and pooling below the bell housing to transmission area. At this point, the leak is worst when the engine is running.

By now, I'm feeling pretty lost. One of the last areas I can think of to check is the intake manifold. Is it possible that the gasket has failed at the back of the manifold and the coolant is leaking down the back of the block? One other area I've read about possible leaks is the timing chain cover. Does anybody have any experience with this location leaking?

I'd really appreciate any help, thanks guys.

 

Are you sure it is coolant? The evaporator drain is near there. It can still be a heater core leaking. The condition of the hoses is irrelevant. Normally you'd be able to smell it though. Put the heat on in the cab. What do you smell?

Rent/borrow a radiator pressure tester and put the system under some pressure so you can find your leak. I would think that if there was a coolant leak at the intake manifold that you'd have seen some evidence of it when you pulled the bell housing.

 

On my '97 3.9, I experienced exactly what you described. No one could spot a leak but I continued to lose coolant.

The intake manifold bolts were corroding, and one of them had broken. Dodge makes a kit apparently to replace all bolts and the intake manifold gasket. I think the repair with labor ran me about $800….

And of course not too long after this, the crank position sensor failed. The coolant had been dripping on it. Who knows if that was the cause of the sensor failure, but my mechanic said he was not surprised.

If I were you, I'd get the intake manifold checked, and if that's the issue, you might want to have a Mopar crank position sensor put in while you're in there. Don't use an aftermarket sensor or you'll end up replacing it twice…..

 

00DakDan: Thanks for the feedback man. Yea, I'm sure it's coolant because it's been leaking and I've been refilling it for a while. Plus it's got the same green tint as the stuff I'm putting in. I still don't think it's the heater core because it's coming out pretty quick when the truck is running and shortly afterward. I'm not seeing any kind of wetness form the inside, nor am I smelling any coolant with the blower and heat on max. If the condition of the hoses don't matter, where would be the culprit? Would I have to remove stuff from the cab to check it out or fix it if it was leaking?

I also wanted to ask about your advice to rent the pressure tester. I may not be understanding the way it works, but if I can't see a pretty good leak while it's running and dripping fluid, how would the pressure tester, which would just allow air to escape from the leak, help me find the leak?

I feel similarly about the whole blacklight testing fluid; just not understanding how it would help me if I can't see a good dripping leak from every possible angle I've attempted.

lambs: Thanks man, sounds like I may be dealing with a similar issue as you. I did get a good look at the crank position indicator/sensor when I pulled the tranny and it was in good shape. I think mine is actually leaking more from the left side, which is opposite the indicator. That's a pretty stiff bill, I know that kit you're talking about and it's not too expensive. I guess there's a lot of work involved with removing the intake manifold.


Anybody else have any other ideas of what to look for / how to test? I may try to replace the manifold this weekend if nobody else has any ideas of what to do next...

 

If you don't smell it it probably isn't the heater core. The core would leak internally, in the HVAC plenum. The hoses would not appear wet. It could leak out the evaporator case drain or onto the floor. If it was leaking then yes, to replace the heater core involves rolling the dash.

The pressure tester puts the system under pressure, just as what happens when the engine is running. You could then check for leaks without the fan blowing the fluid around so you can't tell where it's coming from OR you risking bodily injury/burns while checking for the leak. It's not going to leak air (unless you were out of antifreeze) it would force the antifreeze out the leak.

Basically it's all just to narrow down where the leak is. Fluid runs downhill for the most part so you should see more of the dye at the source and streams leading back to it.

 

I'd fill the system to capacity and check for leaks before pulling the intake. You might be able to spot the leak from underneath if the engine is running and warmed up. It sounds as though it's leaking pretty well, so it might drip down instead of evaporating...good luck and let us know what you learn.