Coolant Leak to Nowhere?

[bk10s]

'02 Sport Trac, 206K. No visible leaks. Smell coolant outside of truck after driving. Reservoir goes down about 20% every 10 days or so. Grrrrrrr. Help!

 

[DILLARD000]

At 206kMiles, assuming you've still got original factory JunkPlastic ThermoStatHousing,
9to1 VegasOdds its the problem; a NotoriousFailureItem,
tends to split along PlastiWeld lower~upper body seam, leaks coolant into engine valley under IntakeManifold.
Makes a smelly swamp that evaporates with engine heat,
until leak gets big enough to actually drip all the way to the ground.

Best to replace\upgrade it with an Aluminum version.
Click here for more on swapping in an Aluminum ThermoStatHousing.

Consider renewing OilPressurized TimingTensioners while TStatHousing is out of the way.
Click here for more on replacing OilPressurized TimingTensioners.

 

[bk10s]

Sounds like a plan, Dillard000. Nice report. I'm thinking about diving in.

 

[DILLARD000]

If you have a garage\driveway space to work in, plus basic wrench set & tools;
yes you can do this yourself; just requires a little patience & a few hours.
Using a flashlight, take a closer look under the ThrottleBody into the EngineV, to confirm the problem.

 

[bk10s]

Upon further investigation (with the flashlight!), it appears that the leak is from the back of the engine, dripping down onto the exhaust pipe. What would that be?

 

[DILLARD000]

Upon further investigation (with the flashlight!), it appears that the leak is from the back of the engine, dripping down onto the exhaust pipe. What would that be?

2 possibilities:
~ the JunkPlastic TStatHousing is leaking back into EngineV, then overflowing to the rear, over+around the TransmissionBellHousing, over the ExhaustPipe to the ground.
~ some early V6~4.0L~SOHC engines were fitted with a PCVValve "WarmingLoop";
this 5/16"ID Hosed loop operates parallel with the 5/8"Hosed Heater loop, runs around the back of the Engine, thru an "OxBow" fitting around the PCVValve on the rear of the left ValveCover. This "RubeGoldberg Invention" never worked well & can leak; I deleted the 5/16" loop & associated OxBow+T fittings several years ago.

 

[bk10s]

Yes, I replaced the PCV about a week ago and thought that setup with the heater loop was a little weird. I'll check again, but no leak when I originally installed. The leak I have started before PCV replacement, and is slowly getting worse. Focusing on that lower thermostat housing.

 

[curtis james]

I still have the plastic factory junk thermo housing and with 60k miles, i keep putting it off and when i drive on trips i walk in front and smell for coolant knowing if i just would replace it i would have a piece of mind but knowing the odds like vegas i have not, kind of like why i go to vegas quite often. stupid , stupid, stupid.. please let us know the end results so it gives me one more reason to replace mine..

 

[Todd Z]

Just replace it..

 

[napierjohn]

Just replaced mine. Did the 2 tensioners since that job gives you easy access to one. Solved the leak and the 'chain slap upon cold start' issue.

 

[Vegas Sporty]

I replaced mine with a factory OEM plastic. I did find the bolt torque for the bolts. I believe this is why some many are having problems with these leaking after an install. Over tightening and warping the whole unit. Other wise go with the all aluminum that's offered. Can't go wrong with it but again find the torque for the bolts to ensure it's not going to fail.

 

[bk10s]

Well, I finished the thermostat housing and timing chain tensioner replacement. Removal and replacement of the tensioners was simple and straightforward. Installing the new thermostat housing was easy. Removal of the lower thermostat housing was a nightmare......bolt was frozen and I couldn't budge it. Ended up having to cut it apart and gently heat and cool the bolt to remove. Replaced lower radiator hose at the same time. SPECIAL THANKS to

DILLARD000​

for all the guidance!

 

[DILLARD000]

Happy to help.
Others in these forums have been great+gracious help for me over the years.
Be sure to report back after a few days\weeks to update us on the success\failure of the repairs.

 

[bk10s]

So.......It is a week later. I'm not sure if the coolant I smell after driving is leaking coolant or from the little that spilled around during the repair of the thermostat housing. It's not like I hosed things down. Also, the coolant level in the reservoir has gone down a little bit over the course of a week. I did pressure check the system after completing the repair. Temperature is perfect, and no visible leaks - Clean as a whistle. Wait a little longer....?

 

[Todd Z]

It takes some time to fully burp if you did not pull a vacuum. I’d also wash it down.

 

[DILLARD000]

Yep. Keep an eye on both the level in the tank & the radiator itself. Do an eyeball inspection under the intake & around the heater hose connections, after driving the next several times.

 

[bk10s]

10-4. New hoses all look great with regular clamps instead of the OEM spring loaded ones.

 

[DILLARD000]

Do check the notorious plastic Tee & HeaterValve; they tend to get brittle & crack with age. If those are ok, then as Tod said, may be just degassing.

 

[bk10s]

All still dry.....AND coolant smell has disappeared. Probably all burned off! Thanks to all!!

 

[bk10s]

Surprise!!! It looks like the water pump is leaking now. Saw a puddle on the garage floor and reservoir is almost empty. Replaced this water pump 2 years ago. Grrrrr.