New coolant leak 07 Mustang V6

[aquariuscsm]

2007 4.0 V6 Mustang. I replaced the cracked leaking thermostat housing. Went back together perfectly. After a few days I noticed a tiny leak/seepage around the base of the coolant temp sensor which is attached to the upper cover of the thermostat housing. I reinstalled the sensor exactly the way it came out. It simply sits inside the hole,held in by a metal clip. Did I perhaps miss something? I don`t recall seeing any kind`ve gasket when I removed it,and the schematic of the cooling system for this car doesn`t show a gasket either. Here`s a pic. That gray plug with the wire attached is the sensor. It`s leaking from underneath the bronze nut at the bottom of it. The sensor is not threaded,therefore doesn`t screw into the housing,it just sits inside the hole held in by the small metal clip.

 

[Donald]

So what seals the sensor? There has got to be something.

Does the metal clip put tension on it to seal? Maybe the clip is weak?

Black Permatex?

 

[Colt45ws]

Yeah, has to be some sort of seal; probably an o-ring. Might be inside the hole on the housing instead of on the sensor itself.

 

[Colt45ws]

Yup, there is an o-ring.

 

[aquariuscsm]

Originally Posted By: Colt45ws
Yup, there is an o-ring.

^^Bingo! Thanks Colt! I bet that tiny o-ring fell off during the repair. I knew there had to be something to seal it.

 

[bdcardinal]

Ford does not sell the o-ring by itself, when we do the housings we usually sell a new sensor. If you go to a dealer and ask for 1W1Z-19E889-BB, that is an AC o-ring that is about as close as you can get to the one on the sensor. The sensor p/n should be 3L8Z-12A648-A if you want to go that route.

 

[aquariuscsm]

Originally Posted By: bdcardinal
Ford does not sell the o-ring by itself, when we do the housings we usually sell a new sensor. If you go to a dealer and ask for 1W1Z-19E889-BB, that is an AC o-ring that is about as close as you can get to the one on the sensor. The sensor p/n should be 3L8Z-12A648-A if you want to go that route.


Got the o-ring from Ford for a lil bit over a dollar. Exact fit,thanks!

 

[01rangerxl]

I will be keeping this thread and the part numbers in mind when dealing with these in the future.

This is one common failure where there is no internet amplification...if anything, it's under-amplification! Every Ford SOHC 4.0 leaks from this stupid plastic housing at some point during its life, but you don't hear much about it. I see these leaking daily. Mostly on Explorers, but also Mustangs and Rangers. I think most people just keep topping off the coolant and driving on it indefinitely. I did an oil change on an '03 Explorer Sport Trac today with over 400K miles on it. It had coolant stains all over and had apparently been leaking from the t-stat housing for a while, but the owners just kept adding coolant.

In general, plastic cooling system parts do not hold up for the long haul. Plastic water necks/t-stat housings, plastic t's, plastic rad tanks, etc. are always the first things to go. Hoses seem to last forever these days, and I don't see many bad t-stats. I see a lot of plastic coolant parts leaking though.