Coolant leak remains after replacing thermostat housings and sensor

[Sweersa]

My 2005 Explorer 4.0 V6 had a coolant leak coming from the lower thermostat housing. Coolant would pool up on top of the engine and drip all over the driveway and make puddles. I replaced both the upper and lower thermostat housings, thermostat (since I was already in there) and the sensor. All new parts were Motorcraft. It's still leaking but now it appears the leak is coming from the sensor on top of the lower housing and then drips all over the place, and the sensor is a little loose too in the lower housing. I remember the original sensor in the original housing fitting a lot more snug. The new sensor came with a new O-ring.

I have heard replacing the O-ring with a slightly larger or fatter one will help. Or to use teflon tape around the O-ring.

Has anyone else experienced this issue? I figured going with Ford recommended Motorcraft parts would prevent something like this from happening.

 

[bizzs]

I think the easiest solution for you would to rent a pressure tester at your local advance auto part store. Basically, its free if you have a credit card to use for a deposit. I had a similar problem and the pressure helped me diagnose exactly where the coolant was leaking. I had replaced all of the parts that you had mentioned finding that the replacement housing had a slight crack in it. This was an OEM dorman, not motorcraft.

 

[swshawaii]

This was an OEM dorman, not motorcraft.

^ That's funny! Dorman aftermarket parts are not known for OEM quality.

Is the ECT sensor retainer clip seated all the way in the housing?

 

[Sweersa]

Thank you both for the suggestions. The clip appears and feels to be seated in all the way.

I just replaced the stock O-ring from the new Motorcraft thermostat sensor with a # 8 O-ring from Home Depot as suggested in other threads. It's slightly larger than the one I removed. It feels a more solid, but still not 100% snug. It does wiggle slightly, not sure if that is normal or not. I topped off the coolant again, and will see how it goes. It did take more force to get it into the housing with the bigger O-ring, so that's a good sign. The clip went in fairly easily as it did before.

If I continue to have issues, I'll consider renting a pressure tester. That's good to know.

As a side note, for anyone else in a similar situation, I had coolant leak all over my serpentine belt. The annoying squeak wouldn't go away as days passed, so I removed it, and replaced it with an old one I kept as a backup after I wiped off the pulleys. The noise went away. The one the coolant messed up was only about a year old, but I ordered a new one anyways since the one I put on there now is really old and it will be a backup after I replace it with the new one coming in.

 

[Sweersa]

I still have a small leak.

I figure spending a tad extra for all Motorcraft parts would have been a good idea for this job, but I was wrong.

Are there two different size ECT sensors for the same model Explorer? If Ford changed the port size in the housing, then I would need the larger sensor. If not, I guess there are some tolerance issues with these parts. I can try some teflon tape to see if that helps.

 

[swshawaii]

Yes, the replacement Motorcraft RH-148 lower housing has a slightly larger sensor hole.

Is your Ford/MC replacement sensor one of the four part numbers listed in the link below?

DY1269 (Alternate/OEM Part Number(s): 3L8Z12A648A, 3L8Z12A648BA, DY1004)
http://www.rockauto.com/en/moreinfo.php?pk=4332630&cc=1430688

 

[Sweersa]

Yes, the replacement Motorcraft RH-148 lower housing has a slightly larger sensor hole.

Is your Ford/MC replacement sensor one of the four part numbers listed in the link below?

DY1269 (Alternate/OEM Part Number(s): 3L8Z12A648A, 3L8Z12A648BA, DY1004)
http://www.rockauto.com/en/moreinfo.php?pk=4332630&cc=1430688

Thank you for the confirmation.

Yes, mine is "MI DY1269" according to the RockAuto packing list. It's the same one your link leads to. I can dig up the box it came in tomorrow to find out for sure.

I assume DY1269 is the smaller one, made to fit the original housing? If that's the case, I'd like to know the part number for the correct sensor for the newer housing with the slightly larger hole.

 

[swshawaii]

DY1269 is the updated and correct sensor designed for the RH-148 housing. Coolant pressure test is fool proof, do it. Baffling. :scratch:

 

[360cid]

I just replaced the lower coolant housing on my 04 a week ago with one from Advanced Auto. The sensor seemed a little loose to me as well, but so far it is not leaking. Will keep a closer eye on it now that I know there are updated sensors!

 

[Sweersa]

DY1269 is the updated and correct sensor designed for the RH-148 housing. Coolant pressure test is fool proof, do it. Baffling. :scratch:

The bag the sensor came in matches the correct part numbers you provided, however, the sensor itself does not match any of those numbers with the numbers it has on it. Please excuse my ignorance, but is that normal? One of the part numbers is fairly close, but none of the numbers on the actual part are a match.

New sensor (Ford part in MotorCraft bag)

Old sensor

 

[swshawaii]

DY1269 is the Motorcraft number and the correct part. Disregard the longer Ford part number in this case. Could you snap a pic of the sensor and clip installed? Also, did you torque the six upper and lower bolts to the factory spec of 7-9 foot pounds? The bolts are often over tightened causing the plastic housings to warp or pinched rubber seals that leak.

Ford Genuine Parts vs. Motorcraft Difference?
http://www.mysporttrac.com/shared/msgboard9e.asp?BOARDNAME=MSG&VIEW=1333014&SUB=1333027

 

[Sweersa]

DY1269 is the Motorcraft number and the correct part. Disregard the longer Ford part number in this case. Could you snap a pic of the sensor and clip installed? Also, did you torque the six upper and lower bolts to the factory spec of 7-9 foot pounds? The bolts are often over tightened causing the plastic housings to warp or pinched rubber seals that leak.

Ford Genuine Parts vs. Motorcraft Difference?
http://www.mysporttrac.com/shared/msgboard9e.asp?BOARDNAME=MSG&VIEW=1333014&SUB=1333027

I didn't use a torque wrench, but did get the fasteners snug using a small ratchet with 8mm socket. Most of the coolant has been wiped/evaporated when I just took this picture, but after a long drive it pools on top of the housing, and runs all over. I added some teflon tape around the O ring part of the sensor today. After installing the larger O ring, it leaked significantly less than it did with the stock one, but it still leaks, which is why I was thinking it was the sensor. I'll know tomorrow how it does with the added teflon tape.

 

[swshawaii]

Definitely a sensor leak. Clip appears seated all the way and properly installed. Must say, with all the failed lower t-stat housing repairs I've NEVER seen an issue of leaking sensors using brand new OEM parts. Just the thought of needing teflon tape to seal is lame. If they were Dorman or Four Seasons parts it wouldn't surprise me. GL, hope it works and keep posted with results.

 

[Sweersa]

Definitely a sensor leak. Clip appears seated all the way and properly installed. Must say, with all the failed lower t-stat housing
repairs I've NEVER seen an issue of leaking sensors using brand new OEM parts. Just the thought of needing teflon tape to seal
is stupid. If they were Dorman parts nothing would surprise me. Good luck, hope it seals and keep us posted with your results.

Will do, that would be just my luck, things like to break or malfunction around me. That's probably why I'm a successful IT technician.

I agree on having to use the tape being stupid, it would bother me a lot more if the engine wasn't a ticking time bomb 4.0 with timing chain noises 190,000+ miles. I'll be happy to get 2-3 more years out of her before needing major work under the hood.

 

[chris8428]

Hi all--

I just replaced my upper and lower thermostat housing this afternoon. I used the new "O" ring that came with the kit on the old sensor. I was concerned as the new "O" ring did not appear quite as wide as the old one but so far nothing is leaking. I did note the sensor has no up or down play in it but will fairly easily rotate side to side when in place (if that makes sense).

As a side note thanks to everyone on the forum for previous threads and pictures on this repair.

Chris

 

[Sweersa]

Here's a final (hopefully) update.

The sensor leaked after using more teflon tape. I took it in to a local trusted mechanic we use for our company fleet. They hooked it up to a pressure tester, and found the large top hose to the radiator was leaking on the end connected to the thermostat housing due to a bad spring hose clamp. They replaced it with a screw type hose clamp, made in the USA too. They didn't even charge me for anything, which was appreciated.

Now it's dry!

I assume fluid was spraying out of that hose on top of the housing while driving, so it looked like the sensor was the culprit, when it was not.

Now I have the leak fixed, and a super secure sensor! I asked the mechanic if I should remove the teflon tape I put on the sensor while troubleshooting, and he said to just leave it since it holds in pressure fine.

Thank you everyone for the help!

 

[bizzs]

"I think the easiest solution for you would to rent a pressure tester at your local advance auto part store. Basically, its free if you have a credit card to use for a deposit. I had a similar problem and the pressure helped me diagnose exactly where the coolant was leaking."

Lol!

I am glad it worked out for you. I think the pressure tester is the best way to track down a coolant leak.

bizzs

 

[Sweersa]

^ I agree! You were right. I just wanted to do as much as I could with what I had. Then I gave up and did what I should have done in the beginning. Haha