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jstaif

Member
Joined
December 9, 2014
Messages
13
Reaction score
0
City, State
Harrison Twp, Mi
Year, Model & Trim Level
2002 Exp XLS 2007 XLT
Greetings, Looking for help on where my coolant is going to...

Have an 02 Explorer with the 4.0 SOHC engine, high miles (286K). Coolant has been disappearing from the system at about 16+ ounces a week but can't find where it is going, have checked the following:

Pressure tested the system, It holds pressure for the 30 minutes + that I have tested it for with no coolant appearing anywhere or any puddles on the ground. Not leaking through any external areas: No hose leaks, not leaking through the thermostat housing (new) or coolant temp sensor. No evidence of pooling on top of engine or anywhere else.
Added the leak trace to the coolant but still found no leaks with black light anywhere under the hood after driving or while pressure testing

Oil looks normal (no milkiness present).

Ran the block tester CO test for at least 30 minutes and fluid stayed blue...no exhaust gases apparent in the coolant.

Bought a new reservoir cap that holds the 16psi.

Nothing noticeable is coming out of the exhaust i.e. smoke etc. Once in a while I smell coolant around the engine but usually not. Coolant might be disappearing at a faster rate when I drive at higher speeds 70mph +.

No other symptoms exist, runs at normal operating temperature. I bought this car new and it has never been allowed to overheat.

Wondering what internal interfaces exist for coolant leaks on this engine. It seems the the plastic intake manifold and exhaust manifold only mate to the head, so no water jacket interfaces are part of these interfaces.

This would leave the Head Gasket coolant interfaces that I have not seen issues with:
1) to the combustion chambers
2) to the outside
3) to the crankcase

I'm feeling kind of stumped here. Am considering using Blue Devil in the coolant. Would like to get a few more years from this old gal.

Any clues on where the coolant is going???
 


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jstaif

Member
Joined
December 9, 2014
Messages
13
Reaction score
0
City, State
Harrison Twp, Mi
Year, Model & Trim Level
2002 Exp XLS 2007 XLT
Greetings, Looking for help on where my coolant is going to...

Have an 02 Explorer with the 4.0 SOHC engine, high miles (286K). Coolant has been disappearing from the system at about 16+ ounces a week but can't find where it is going, have checked the following:

Pressure tested the system, It holds pressure for the 30 minutes + that I have tested it for with no coolant appearing anywhere or any puddles on the ground. Not leaking through any external areas: No hose leaks, not leaking through the thermostat housing (new) or coolant temp sensor. No evidence of pooling on top of engine or anywhere else.
Added the leak trace to the coolant but still found no leaks with black light anywhere under the hood after driving or while pressure testing

Oil looks normal (no milkiness present).

Ran the block tester CO test for at least 30 minutes and fluid stayed blue...no exhaust gases apparent in the coolant.

Bought a new reservoir cap that holds the 16psi.

Nothing noticeable is coming out of the exhaust i.e. smoke etc. Once in a while I smell coolant around the engine but usually not. Coolant might be disappearing at a faster rate when I drive at higher speeds 70mph +.

No other symptoms exist, runs at normal operating temperature. I bought this car new and it has never been allowed to overheat.

Wondering what internal interfaces exist for coolant leaks on this engine. It seems the the plastic intake manifold and exhaust manifold only mate to the head, so no water jacket interfaces are part of these interfaces.

This would leave the Head Gasket coolant interfaces that I have not seen issues with:
1) to the combustion chambers
2) to the outside
3) to the crankcase

I'm feeling kind of stumped here. Am considering using Blue Devil in the coolant. Would like to get a few more years from this old gal.

Any clues on where the coolant is going???

Forgot to mention, the plugs all looked normal and the same as each other.
 




974X4BLACKSPORT

Well-Known Member
Joined
May 21, 2018
Messages
963
Reaction score
231
Location
FL
City, State
hudson
Year, Model & Trim Level
BLACK 1997 SPORT 4 BY 4
There is a vacuum operated servo that diverts hot water away from the heater core when the temp. select knob is on full "cold", this servo can leak small amounts of coolant out of the servo shaft seal when you are not looking. I think its called "temperature divert valve". Follow your heater hoses from the engine block all the way to the fire wall, it will be located on one of those heater hoses.
 




jstaif

Member
Joined
December 9, 2014
Messages
13
Reaction score
0
City, State
Harrison Twp, Mi
Year, Model & Trim Level
2002 Exp XLS 2007 XLT
There is a vacuum operated servo that diverts hot water away from the heater core when the temp. select knob is on full "cold", this servo can leak small amounts of coolant out of the servo shaft seal when you are not looking. I think its called "temperature divert valve". Follow your heater hoses from the engine block all the way to the fire wall, it will be located on one of those heater hoses.
Went out and looked at this valve, it’s dirty but dry. Will monitor it. Thx.
 




Tshaw88

Active Member
Joined
July 28, 2019
Messages
65
Reaction score
6
City, State
RI
Year, Model & Trim Level
05 Explorer Eddie Bauer
Look on top of the block between the fuel rails behind the thermostat housing. Bottom gasket of therm housing is known to leak and coolant goes down onto the block, usually puddles in a freeze plug.
 




jstaif

Member
Joined
December 9, 2014
Messages
13
Reaction score
0
City, State
Harrison Twp, Mi
Year, Model & Trim Level
2002 Exp XLS 2007 XLT
I had this issue with my wifes car, so I've been keeping an eye out for that. This car came with an NVH foam "pillow" which I took out so I could see the top of the block. Thanks for responding.
 




sfhess

Active Member
Joined
December 10, 2012
Messages
69
Reaction score
0
City, State
Palmdale CA
Year, Model & Trim Level
2002 Explorer XLT RWD V6
I just replaced all the hoses, o-rings and seals having to do with the thermostat housing. Had to improvise a bit on the hoses and one seal was particularly hard to find. Eliminated my leakage into the valley under the intake plenum.
 








Tshaw88

Active Member
Joined
July 28, 2019
Messages
65
Reaction score
6
City, State
RI
Year, Model & Trim Level
05 Explorer Eddie Bauer
My 05 didn't have the foam pillow, the motor I just put in was from an 02 and did have it, I left it in its supposed to help dissipate the heat I guess and where the intake it plastic I figured I'd leave it. I've run blue devil coolant stop leak through mine in the past, even if it doesn't seal the leak it does a good job of showing where it's leaking, I always pull the thermostat and clean up the thermostat and inside the housing afterwards though and put in fresh coolant just to be sure the stuff doesn't gunk up the thermostat on me.
 




sfhess

Active Member
Joined
December 10, 2012
Messages
69
Reaction score
0
City, State
Palmdale CA
Year, Model & Trim Level
2002 Explorer XLT RWD V6
"Blue Devil" is costly and worthless.
 




Tshaw88

Active Member
Joined
July 28, 2019
Messages
65
Reaction score
6
City, State
RI
Year, Model & Trim Level
05 Explorer Eddie Bauer
Depends how u use it, I add it at the thermostat let it run, spot the leak then dump the coolant, clean the thermostat and put it fresh coolant, I've only needed it twice to find leaks. It's not something is let stay in the heating system I learned that lesson the hard way.
 




TechGuru

Explorer Addict
Joined
August 23, 2015
Messages
2,102
Reaction score
278
Location
Texas
Year, Model & Trim Level
2003 XLS 4X4 4.0L FLEX
The only stop leak I'd use is this:

1196_web.png

I've used it without any problems. It's best for these hard to find tiny leaks.
 




Gilligan

Member
Joined
October 30, 2017
Messages
25
Reaction score
4
City, State
Colorado Springs
Year, Model & Trim Level
2004 Ford Explorer Sport
I've had a siiliar issue and found I needed to replace my pinch clamp hose clamps with full metal screw tight belt clamps. Fluid was leaking around the hose fittings but with the engine heat the evidence evaporated away.
 




sfhess

Active Member
Joined
December 10, 2012
Messages
69
Reaction score
0
City, State
Palmdale CA
Year, Model & Trim Level
2002 Explorer XLT RWD V6
I had my upper radiator hose, "secured" by the original spring clamp, blow off the radiator bung. I replaced the original spring clamps with worm screw clamps.
 




Drewmcg

Elite Explorer
Joined
August 27, 2015
Messages
733
Reaction score
91
Location
Michigan
City, State
Ann Arbor, MI
Year, Model & Trim Level
2010 XLT 4WD
2002 XLS 2WD
The only stop leak I'd use is this:

1196_web.png

I've used it without any problems. It's best for these hard to find tiny leaks.

Tech Guru: What product were you trying to show? Tx.
 








blue xlt

Member
Joined
August 21, 2004
Messages
25
Reaction score
0
City, State
queens ny
Year, Model & Trim Level
00 xlt
Starting with engine cold,start engine and let it fast idle for 90 seconds. Shut off engine and get under truck at rear of engine and look up with strong flashlight. Your looking for coolant dripping down or greenish/yellow stains.By running for 90 sec,you are pressuring coolant system but engine is not hot enough to burn off fluid and leave no trace. Good luck.
 








Derrick Stoelton

New Member
Joined
September 30, 2019
Messages
3
Reaction score
0
City, State
Crystal River, FL
Year, Model & Trim Level
2003 Explorer Eddie Bauer
Have you checked your oil cooler gasket?
 


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Elite Explorer members see no advertisements, no banner ads, no double underlined links, can add their own profile photo, upload photo attachments in all forums, and Media Gallery, create and save more private conversations, and more. Join Today. Your support is greatly appreciated.








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