P0401 and losing coolant

[dopexile]

My 2004 Ford Explorer XLT is displaying the error code P0401 Insufficient EGR Flow and recently started burning coolant. The reservoir goes empty after about a week.

I took the car to the dealer and they were quick to tell me that the coolant loss was likely a bad head gasket and wanted me to trade the car in (which is how they really make money).

I researched this code and determined that it is likely the DPFE sensor or the EGR valve itself. Is it possible that the EGR valve or DPFE could be causing the coolant loss?

 

[plasticseng]

I doubt that the coolant loss is related. I can't think of any way it could be.

The DPFE sensor is the normal culprit with that code, but there a lot of YouTube videos on troubleshooting that code if want to verify before replacing it.

 

[imp]

I doubt that the coolant loss is related. I can't think of any way it could be.

The DPFE sensor is the normal culprit with that code, but there a lot of YouTube videos on troubleshooting that code if want to verify before replacing it.

@plasticseng Back in the early '90s, Mustang 5.0L HO engines had a liquid-cooled block between the throttle body and upper intake manifold. Was it the entry-point for the EGR gas? Where does the EGR gas enter Explorer 4.0L?

Interesting side-note, 1993 Mustang Cobra had NO such spacer block. imp

 

[plasticseng]

@plasticseng Back in the early '90s, Mustang 5.0L HO engines had a liquid-cooled block between the throttle body and upper intake manifold. Was it the entry-point for the EGR gas? Where does the EGR gas enter Explorer 4.0L?

Interesting side-note, 1993 Mustang Cobra had NO such spacer block. imp

On my 2002, there is no water anywhere on the intake. The intake is one piece. I believe the 2004 is the same in that regard.

 

[Tech By Trade]

That is correct, all the SOHC have a dry plastic intake. Is it burning or leaking coolant? Thermostat housings like to flood the valley, and the plastic tanks like to leak on the rads. 230k kms on my 07 and I'm on my second thermostat and third rad.

 

[dopexile]

That is correct, all the SOHC have a dry plastic intake. Is it burning or leaking coolant? Thermostat housings like to flood the valley, and the plastic tanks like to leak on the rads. 230k kms on my 07 and I'm on my second thermostat and third rad.

It seems like it is burning it. I did a pressure test and no signs of a leak.

 

[Tech By Trade]

Pop the cap off the rad and look for bubbles when its warming up I guess. Probably cheaper and less hassle to just replace the engine with one out of a wreck if it is shot.

 

[dopexile]

Nevermind... I found a leak on the r134a line that I thought was coolant related.

 

[dopexile]

I think I may have figured this one out...

I put UV dye into my coolant and did another pressure test and with the help of my 4 year old son noticing a puddle we found some leakage in the driver's rear quarter panel... is this for the rear hvac system?

Thoughts on next steps?

Thanks

 

[imp]

@dopexile Good detective work! What pressure do you think you applied, any idea? Obviously, normal operating (~16 psi) did not cause this much, or you likely would have noticed the leak. OTOH, did the pressure level you put in, cause a new leak? imp

 

[bizzs]

Yes. I did this repair to my 03 explorer. I had a leak at the same location and it was the rear heater core. The metal pipe was rotted out at the joint. You need to buy heater hose and clamps. Cut the rotted piece off and splice the new piece in. I replaced the entire length out to the frame. The splice worked out well for me and it was a cheap fix. There is a post on here regarding replacing the rear actuator motor and it explains how to disassemble the interior side bezzle to gain access to the heater core. I followed the directions and made the repair within 4 hours.

Good Luck
bizzs

 

[dopexile]

I raised the pressure to 18psi when the leak started. The cap and overall system is rated for 16 PSI so that's a little high.

I put some clamps on it and it is no longer leaking, but I'm not sure if that is my main problem.

A few observations:

1) When pumping the pressure up to 18 PSI, it slowly falls down to 10 and then holds pressure. Not sure if that is a problem or not
2) I let all the pressure out (0 PSI) and turned the car on and let it warm up. Pressure didn't really build up.
3) With the engine warmed up and running I then increased the pressure to 15 PSI and it held at around 8-10 PSI. This leads me to believe the head gasket is not blown (wouldn't it not be able to build pressure if there was a head gasket leaking)?

I'm wondering if the dealer was just trying to sell me a new car. I can't really drive the car right now because it has a broken wheel hub bearing so I can't tell if its still losing coolant.

I think the p0401 error is unrelated and the EGR valve needs to be swapped out.

I will post when I know more... if anyone can think of tests or checks to do I would appreciate it.