Coolant leak?

[DILLARD000]

...intake manifold it's a little oily...

Won't hurt to replace or at least clean the PCVValve with Carb\Throttle spray, make sure it rattles.
Not sure if you have the older PCValve with the CoolantOxBow or the newer design with an ElectricHeater?
Consider deleting that PCVCoolantLoop, & it's 5/16" Hoses+Tees, & the Coolant OxBow around the PCVValve;
it's a useless "Rube Goldberg" design that's little more than a source of coolant leaks.
Part on the right side of the IntakeManifoldThroat, I call it the PCVCoolantHeatExchanger;
I ground off those two 5/16"CoolantHoseBarbs & re-installed with a little RTV smear around the ORing at the Manifold.
Be sure to check that 5/8" PCV vacuum hose+tube assembly; the rubber L hoses on the ends are known to crack\leak & cause trouble codes.

 

[dashhho]

Won't hurt to replace or at least clean the PCVValve with Carb\Throttle spray, make sure it rattles.
Not sure if you have the older PCValve with the CoolantOxBow or the newer design with an ElectricHeater?
Consider deleting that PCVCoolantLoop, & it's 5/16" Hoses+Tees, & the Coolant OxBow around the PCVValve;
it's a useless "Rube Goldberg" design that's little more than a source of coolant leaks.
Part on the right side of the IntakeManifoldThroat, I call it the PCVCoolantHeatExchanger;
I ground off those two 5/16"CoolantHoseBarbs & re-installed with a little RTV smear around the ORing at the Manifold.
Be sure to check that 5/8" PCV vacuum hose+tube assembly; the rubber L hoses on the ends are known to crack\leak & cause trouble codes.

I got a new PCV. It has the oxbow coolant heater - will deleting this impair the function of the PCV? I do live up north in a cold climate that gets much snow. I got a new PCV tube/hose system so the lines will be new!

 

[DILLARD000]

...got a new PCV...has the oxbow coolant heater
...will deleting this impair the function of the PCV? I do live up north in a cold climate that gets much snow.
...I got a new PCV tube/hose system so the lines will be new!

Here at 9000ft 2743m in the RockyMountains with 6mth long winters, no problems after 2 years wOut the PCVCoolantLoop.
Consider the PCVCoolantLoop does NOT circulate unless the Driver switches on CabHeat;
the HeaterCore 5/8" Loop & the PCVCoolantLoop operate parallel controlled On\Off by the HeaterControlValve.
99% of the time, I warm up the truck on ColdStarts for 2~5min before driving, with the CabHeat off (thus PCVCoolantLoop off).
Considering the PCVValve is directly above the left ExhaustManifold, & the PCVHeatExchanger is directly above the EngineBlock,
which both warm up faster than the Coolant hoses, I believe there's really no lack of warming heat for the PCV components.
When I found a crack+leak in the Factory prefab 5/8~5/16~5/8" Tee+Hose assembly at the back end of the PCVCoolantLoop,
& then route traced the 5/16" hose & realized what it was & how it operated,
that really made the decision for me to delete the entire PCVCoolantLoop,
including the steel 5/8~5/16~5/8" Tee assembly bolted to the right side of the engine.
It's a personal judgement call.
Note I use this truck for winter plowing, but most winter nights its parked in a cozy 40f garage.
It's earned it's keep this year with 5+ ft of snow in March.

PCVValve with CoolantOxBow deleted.

PCVHeatExchanger With 5/16'HoseBarbs deleted.

 

[Bronc3]

I am going to have to look at eliminating the PCV coolant setup on our 4.0, I was considering replacing all the hoses as they are getting old. Might be fine just to eliminate potential leaks.

 

[dashhho]

Got everything reinstalled and leaks fixed. Now onto the next thing.

The truck stumbles slightly for a split second when the AC compressor engages at idle. Its not a huge stumble - but enough that you can notice it. Does this sound like the IAC valve?

 

[DILLARD000]

...onto the next thing.
...stumbles slightly for a split second when the AC compressor engages at idle...enough that you can notice it
...IAC valve?

Do you know what these IACValve-Controlled RPMs are?
...IdleRPMs @ColdStart +00sec, should be >1500rpms
...IdleRPMs @ColdStart +15sec, should be ~1050rpms
...IdleRPMs Warm InPark ACOff, should be ~800rpms
...IdleRPMs Warm InPark ACMax, should be ~750rpms
...IdleRPMs Warm InGear ACOff, should be ~750rpms
...IdleRPMs Warm InGear ACMax, should be ~700rpms
Click here for info on Cleaning+Tuning the IACValve.

If the ThrottleBody MinimumIdleScrew has been mistakenly adjusted up\down,
it may need to be reset to allow the above proper RPM values.
Hope this helps.

 

[dashhho]

Do you know what these IACValve-Controlled RPMs are?
...IdleRPMs @ColdStart +00sec, should be >1500rpms
...IdleRPMs @ColdStart +15sec, should be ~1050rpms
...IdleRPMs Warm InPark ACOff, should be ~800rpms
...IdleRPMs Warm InPark ACMax, should be ~750rpms
...IdleRPMs Warm InGear ACOff, should be ~750rpms
...IdleRPMs Warm InGear ACMax, should be ~700rpms
Click here for info on Cleaning+Tuning the IACValve.

If the ThrottleBody MinimumIdleScrew has been mistakenly adjusted up\down,
it may need to be reset to allow the above proper RPM values.
Hope this helps.
View attachment 58687

Thanks Dillard. I'll get some numbers today - I'm pretty sure at cold start it hits 2000rpm but will double check.

Don't remember my throttlebody having an adjustment screw on it but will check again.

 

[dashhho]

My numbers in yellow. I gave the IACV a clean and it didn't make any noticeable change. When the AC clutch kicks in with the low idle it stumbles for a second, then clutch disengages and it settles - rinse and repeat.

I'll see if I can find an IACV at the wrecker for cheap and try it.

...IdleRPMs @ColdStart +00sec, should be >1500rpms 1900-2000
...IdleRPMs @ColdStart +15sec, should be ~1050rpms ~1050
...IdleRPMs Warm InPark ACOff, should be ~800rpms ~700
...IdleRPMs Warm InPark ACMax, should be ~750rpms ~680
...IdleRPMs Warm InGear ACOff, should be ~750rpms ~680
...IdleRPMs Warm InGear ACMax, should be ~700rpms ~625

 

[DILLARD000]

Those look OK, except the 625rpms seems a little low.
Check the ThrottleBody MinimumIdleScrew on the end of the ThrottlePlateShaft;
I'd set the minimum RPMs up just a small bit, closer to 700rpms.
May be why you're seeing the engine stutter when the AC Compressor engages?

 

[dashhho]

Mines a 2005. I can't see the other end of the screw as it's on the bottom of the throttle body but it kinda feels like you can adjust it? My old 94 ranger had a huge honking screw head but this one's just a little tiny nub. Will try tomorrow.

On second thought when installing the TPS I did have to rotate it slightly after getting it on to get the screws in...the shop manual says that is the procedure for the 3.0L but not the 4.0L. the spline on the TPS would not line up with the shaft on the throttle body unless I rotated it a little, wonder if that's my problem.

This reminds me that I need a new multi meter...are there any cheap obd2 devices that give live diagnostic data like voltage on senors?

 

[DILLARD000]

Yep, that MinimumIdleScrew is mounted upside down,
under the ThrottleCable spool+spring, on the left side of the ThrottleBody.
A smaller HexHead bolt, forget what size.; use a long OpenEndWrench or ViceGrips; a little awkward to get to & adjust.
Remove the "4.0L SOHC" vanity cover for better access.

The TPS is just a 3Wire Potentiometer\Resistor; it's OK to rotate the spline to line up with the ThrottleShaft.
Easy to check with an OhmMeter on the unplugged ConnectorPins; rotate & look for a smooth change in resistance.
PinA~PinC should measure ~3300ohm total; PinB is the signal out & varies with position\rotation.

I have these items:
~ Fluke DigitalMultiMeter; 30+ years old now & still a great meter.
~ OBDLink# MX+ module; uses OBD2Port~WirelessBT~AndroidPhon for routine maintenance & viewing items while driving.
~ OBDLink# EX module; uses OBD2Port~CabledUSB~WindowsPC for indepth maintenance & configurations.
The MX+ is ~$100; EX is ~$50; their are many less expensive\capable & much more expensive\capable OBD2 options.
Click here for more info on the OBD2 items.

 

[dashhho]

Yep, that MinimumIdleScrew is mounted upside down,
under the ThrottleCable spool+spring, on the left side of the ThrottleBody.
A smaller HexHead bolt, forget what size.; use a long OpenEndWrench or ViceGrips; a little awkward to get to & adjust.
Remove the "4.0L SOHC" vanity cover for better access.

The TPS is just a 3Wire Potentiometer\Resistor; it's OK to rotate the spline to line up with the ThrottleShaft.
Easy to check with an OhmMeter on the unplugged ConnectorPins; rotate & look for a smooth change in resistance.
PinA~PinC should measure ~3300ohm total; PinB is the signal out & varies with position\rotation.

I have these items:
~ Fluke DigitalMultiMeter; 30+ years old now & still a great meter.
~ OBDLink# MX+ module; uses OBD2Port~WirelessBT~AndroidPhon for routine maintenance & viewing items while driving.
~ OBDLink# EX module; uses OBD2Port~CabledUSB~WindowsPC for indepth maintenance & configurations.
The MX+ is ~$100; EX is ~$50; their are many less expensive\capable & much more expensive\capable OBD2 options.
Click here for more info on the OBD2 items.

I took another look under the hood and noticed the serp belt looked a little old. It wasn't horrible but definitely not new. I tossed a new one in and so far it hasnt stumbled when the AC compressor kicked on - I'm wondering if the belt was slipping and would put sudden load on the engine when it eventually caught a ridge to pull on.

 

[DILLARD000]

Personal preference for a SerpBelt is
GoodYear#GatorBack=Continental#Elite;
a quality very grippy belt, at a good low price.

 

[dashhho]

Well the thermo housing is seeping a bit at the connection to the motor. I'm thinking it's from the pitting in the aluminum. The gasket/torque seems pretty small to really seal with a pressurized system. I'm thinking of RTVing the housing to the motor and torque it down slightly higher than spec. Thoughts?

 

[DILLARD000]

Well the thermo housing is seeping a bit at the connection to the motor. I'm thinking it's from the pitting in the aluminum. The gasket/torque seems pretty small to really seal with a pressurized system. I'm thinking of RTVing the housing to the motor and torque it down slightly higher than spec. Thoughts?

Assuming you've got a junk Plastic ThermoStatHousing?
Suspect junk plastic Housing has a crack\leak on the back side body seam; very likely at 16+ years old.
Strongly recommend replacing the junk Plastic with a new Aluminum TStatHousing;
any aluminum version is better than any plastic version, so take your pick. More info at
https://2001fordexplorersporttrac.fandom.com/Engine_Coolant_ThermoStat