1998 4.0 engine using coolant no coolant in oil?

[bobwilliams123]

Hi everyone, thank you for allowing me into your brain trust!

My friend has a 4.0 1998 explorer. His engine was using coolant so he removed the heads and sent them to a machine shop and reassembled the engine. He's using about a gallon of water every week or 2 with no leak on the pavement and no steam out of the tailpipe. The oil is clear other than a small amount of milkshake on the inside of the oil fill cap. He's been driving the explorer for about 3 months and has no problems other than a slight misfire that appears to be unrelated to a low coolant condition and the temp gauge does not indicate a problem. He adds water when he thinks about it. He has little background in engines. I've been fixing cars for 50 years and none of this makes, mechanically wise, sense to me so I need your help.

He drove the explorer to my house the other day. He drove about 40 miles on the freeway and when I examined the engine it ran perfect. We added about 12 ounces of water into the radiator which was not under any pressure. It's my limited understanding that the intake manifold has no coolant running through it. The only theory that I've come up with is that there is a coolant leak on the engine deck which is being sucked into a intake manifold gasket leak.

Any ideas?

Thank you.

Bob

 

[XLTrunner]

If it has the SOHC engine, suspect a bad thermostat housing. It is a well known fact that they leak...and often with no obvious signs. My personal experience is that mine would leak into the engine valley and evaporate with the engine heat until one day it became so bad that it actually pooled and would run down the back of the block onto the ground if I parked at an incline. If this is, in fact, the problem, I (and, just about every other owner on this forum) would recommend spending the extra money and installing a metal housing instead of another plastic one that will inevitably leak again.

 

[donalds]

4.0 SOHC Metal Thermostat Housing Comparison

I obtained 2 thermostat housings for my 2001 Ranger. The original is plastic and not leaking yet but you know how that goes on the 4.0 SOHC. The first one is from Simmons Autosports. I have used theirs before and its a great part, way better than the original plastic one from Ford. Here are...

www.explorerforum.com

 

[bobwilliams123]

Thank you for your replies. Now I have something to go on. I'll investigate the thermostat issue and get back to you. Again, thank you very much!

 

[bobwilliams123]

Thank you for your replies. Now I have something to go on. I'll investigate the thermostat issue and get back to you. Again, thank you very much!

It's a SOHC and either his Radiator cap is bad and/or the leak is relieving pressure. He can pull the cap off after driving without spewing coolant. We poured about 12 to 16 ounces of water in the radiator to fill it up.

My driveway is steep, if we replaced the cap and aimed the explorer downhill would that cause the leak to expose itself? Please Advise, Thank you very much.

 

[XLTrunner]

Remove the plastic engine cover (one that says "4.0 SOHC") and, with a pen light flashlight, look behind and around the base of the t-stat housing for signs of coolant leakage. It's still tight in there to get a good look...but at the right angle, you can also get a peek at the forward part of the engine valley behind the housing to see if there is any coolant pooling.

 

[bobwilliams123]

Remove the plastic engine cover (one that says "4.0 SOHC") and, with a pen light flashlight, look behind and around the base of the t-stat housing for signs of coolant leakage. It's still tight in there to get a good look...but at the right angle, you can also get a peek at the forward part of the engine valley behind the housing to see if there is any coolant pooling.

Thank you!

 

[bobwilliams123]

Thank you!

Does a 98 40 SOHC have the two piece that has no coolant flow? I understand that they are known to have gasket leaks that I assume to be oil or vacuum. Thank you.

 

[XLTrunner]

That is correct...upper and lower plastic intake manifolds. And, no...there is no coolant, oil, whatever that flows thru them. Only air. There is a gasket set between the two and a gasket set between the lower and engine. They are also prone to vacuum leaks due to old, hardened gaskets and will usually trigger lean codes PO171 & PO174.

 

[bobwilliams123]

That is correct...upper and lower plastic intake manifolds. And, no...there is no coolant, oil, whatever that flows thru them. Only air. There is a gasket set between the two and a gasket set between the lower and engine. They are also prone to vacuum leaks due to old, hardened gaskets and will usually trigger lean codes PO171 & PO174.

thanks!

 

[bobwilliams123]

List of suspects for coolant leaks on 1997~2012 Ford V6~4.0L~SOHC engines:
~ JunkPlastic ThermoStat Housing, FactoryOE or AfterMarket
~ JunkPlastic Tee for the PCVCoolantLoop 5/16" Hoses operating parallel with HeaterCoolantLoop 5/8" Hoses
~ JunkPlastic HeaterControlValve, FactoryOE or AfterMarket
~ JunkPlastic Tanked Radiator, FactoryOE or AfterMarket
~ Coolant Pump Bearings\Gasket
~ Any Coolant Hose\Clamp especially if FactoryOE
~ HeaterCore
Hope this helps. More info at

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I studied the thermostat housing and associated setup, it's no walk in the park to do it right and I've been wrenching on cars for 50 years. There's very little service factor.

Would it be prudent to remove the intake to get good access to the thermostat and hoses and nipples?

You guys have saved me a lot of work and I am grateful for your assistance.

 

[XLTrunner]

I guess if you're reasonably certain the leak isn't at the radiator, water pump, heater core, heater control valve or various hoses, it's probably time to delve into further inspection of the t-stat housing...and, that will require removing the upper intake manifold. That will allow a better view of the backside and the engine block valley. There are (8) T-30 torx head screws securing the upper intake to the lower along with the various hose connections. Be forewarned, the tube from the EGR into the upper intake may give you fits when trying to lift the intake off the engine. Make sure you buy a new green O-ring gasket for that (Mahle G32745 for example). If you go this far, may as well remove the lower intake as well and replace those gaskets if they've never been done (Mahle MS16375 upper/lower set for example).

If you do find the t-stat housing is the culprit and needs replacing, you'll likely run into another p.i.t.a. scenario where the pigtail wiring that runs down to the crankshaft sensor runs snugly over the middle of the t-stat housing with no slack to allow the housing to be removed. That will require removing the alternator and it's mounting bracket in order to release a retaining clip that secures the wiring to the front of the block in order to allow enough slack to lift the t-stat housing up and off the block. Just adds to the fun factor.

 

[bobwilliams123]

I guess if you're reasonably certain the leak isn't at the radiator, water pump, heater core, heater control valve or various hoses, it's probably time to delve into further inspection of the t-stat housing...and, that will require removing the upper intake manifold. That will allow a better view of the backside and the engine block valley. There are (8) T-30 torx head screws securing the upper intake to the lower along with the various hose connections. Be forewarned, the tube from the EGR into the upper intake may give you fits when trying to lift the intake off the engine. Make sure you buy a new green O-ring gasket for that (Mahle G32745 for example). If you go this far, may as well remove the lower intake as well and replace those gaskets if they've never been done (Mahle MS16375 upper/lower set for example).

If you do find the t-stat housing is the culprit and needs replacing, you'll likely run into another p.i.t.a. scenario where the pigtail wiring that runs down to the crankshaft sensor runs snugly over the middle of the t-stat housing with no slack to allow the housing to be removed. That will require removing the alternator and it's mounting bracket in order to release a retaining clip that secures the wiring to the front of the block in order to allow enough slack to lift the t-stat housing up and off the block. Just adds to the fun factor.

My friend and his pal have been through this engine twice in the last 3 years for the same problem which is leaking coolant that they assumed was a head gasket. He bought a new radiator cap and it's not holding pressure and if the leak was relieving coolant pressure it would have overheated just driving the 40 miles to my house and he drives it everywhere and adds water when he thinks about it. He doesn't know how long it takes to reach operating temperature or where the temp needle should be or if the temp needle ever went to hot. He said it never steams over. I'm reminded of a Toyota Celica that I put brake pads on back in the eighties driven by my friends wife. When I test drove it to bed in the pads the temp needle was pegged on hot but the car ran normally. There was a hole halfway down the radiator. I let it sit for a couple of hours at their house to cool and filled it up with water and started it up and it ran like crap and she started to complain that I damaged her car. So I told her it's normal when you put top of the line brakes on a Toyota and it will smooth out in 15 minutes which it did once the water was evacuated out of the heads. She drove the car for several more years with the needle pegged on hot of course I never touched it again. If I pressurize this Explorer engine it might disable it for some unknown reason. He has certainly run the heads dry because he thinks he added a gallon or two here and there. I'm not saying the engine is possessed by a demon, but if it ain't broke don't fix it and the Toyota Celica comes to mind. I'll bet the farm that once that engine has slippery coolant and 5 pounds of pressure it's going to croak. Thanks for your help! If he does something I'll let you know, I am curious as heck!

 

[bobwilliams123]

Depends on your manifold style; some are easier to work around than others. I did not want to disturb those gaskets, thus the modified 27mm socket.

Will a heater valve or other coolant circuit devise leak down the firewall and run under the floorpan and evaporate leaving no witmess?

Depends on your manifold style; some are easier to work around than others. I did not want to disturb those gaskets, thus the modified 27mm socket.

What's the modified 27 MM socket used for?

 

[XLTrunner]

Dilliard...your info confuses me. I've removed several t-stat housings on my own '98 and a few others at the local JY. There is no way you can remove the housing without first removing the upper intake manifold AND that pigtail wiring that runs snugly over the top of the housing and to the crankshaft sensor. That t-stat housing needs to be lifted pretty much straight up in order to not break off the three plastic tabs on the bottom and risk them dropping into the engine. Perhaps on some later years, the housing can be removed without the intake being removed...I don't know. But, I've done enough of these where I actually timed myself a week ago on a JY '98 and got the upper intake off in 15 minutes...and, that opened up the entire area for much easier access. Also, I'm not sure what you're referring to with PCV Coolant Loop hoses/clamps/tees. There is only an emission hose from the block to the PCV where it's then teed off into two hoses; one each running to either side of the upper intake. No coolant involved.

 

[C420sailor]

100% the housing. Mine lost coolant to the ether for a long time before it got bad enough to pool in the valley and run down the front of the motor.

 

[donalds]

When I changed my thermostat housing I had to remove
Belt
Throttle body
Fan
alternator
Idler pulley
Belt tensioner
And alternator bracket
Then change it out

No intake removal required
Be sure to change the bypass hose

 

[c47@pacbell.net]

Hi everyone, thank you for allowing me into your brain trust!

My friend has a 4.0 1998 explorer. His engine was using coolant so he removed the heads and sent them to a machine shop and reassembled the engine. He's using about a gallon of water every week or 2 with no leak on the pavement and no steam out of the tailpipe. The oil is clear other than a small amount of milkshake on the inside of the oil fill cap. He's been driving the explorer for about 3 months and has no problems other than a slight misfire that appears to be unrelated to a low coolant condition and the temp gauge does not indicate a problem. He adds water when he thinks about it. He has little background in engines. I've been fixing cars for 50 years and none of this makes, mechanically wise, sense to me so I need your help.

He drove the explorer to my house the other day. He drove about 40 miles on the freeway and when I examined the engine it ran perfect. We added about 12 ounces of water into the radiator which was not under any pressure. It's my limited understanding that the intake manifold has no coolant running through it. The only theory that I've come up with is that there is a coolant leak on the engine deck which is being sucked into a intake manifold gasket leak.

Any ideas?

Thank you.

Bob

I have and 07 SporTrac with the 4.0 and at 101k miles that famous thermostat housing let go. For almost a year, I would get a wiff of coolant when walking around the front of the truck after parking, and I would check under the hood, but never saw anything. This was years ago now, and I didn't know about the aluminum replacements available. The replacement plastic unit is still in place and it's been about 5 yrs, I fully expect to have to replace it again someday, but I don't drive it as much now and it only has 139K miles, still doing fine. But until it let go, there was never coolant on the ground under the truck, I think the slow leak would evaporate somehow, and I could never find a sign until the housing cracked open.

 

[EDWARDCASE]

What does the uv leak detector die show under black light?

 

[merlin0152]

Hi everyone, thank you for allowing me into your brain trust!

My friend has a 4.0 1998 explorer. His engine was using coolant so he removed the heads and sent them to a machine shop and reassembled the engine. He's using about a gallon of water every week or 2 with no leak on the pavement and no steam out of the tailpipe. The oil is clear other than a small amount of milkshake on the inside of the oil fill cap. He's been driving the explorer for about 3 months and has no problems other than a slight misfire that appears to be unrelated to a low coolant condition and the temp gauge does not indicate a problem. He adds water when he thinks about it. He has little background in engines. I've been fixing cars for 50 years and none of this makes, mechanically wise, sense to me so I need your help.

He drove the explorer to my house the other day. He drove about 40 miles on the freeway and when I examined the engine it ran perfect. We added about 12 ounces of water into the radiator which was not under any pressure. It's my limited understanding that the intake manifold has no coolant running through it. The only theory that I've come up with is that there is a coolant leak on the engine deck which is being sucked into a intake manifold gasket leak.

Any ideas?

Thank you.

Bo

My 2016 Explorer has a heater core both in the front (typical) as well as the rear, for the rear heating vents. I was experiencing some coolant "consumption" as well. Tricky diagnosis as it started shortly after I flushed and changed my coolant; led me down the wrong thought path at first. Oil was also fine. A little bit of a smell in the cabin, but nothing definitive. I saw some puddling under the weep holes of the dual exhausts, seemed like more on the driver's side than the passenger. We were still running A/C so condensation was expected. Made a mental note and kept checking and topping off to determine the extent of the fluid loss. Finally took it into the dealer and it was, in fact, a leak in the rear heater core. It is housed (on mine) on the driver's side in the cargo area. Due to the location, I believe the leak was making its way under the cargo area and dripping from the exhaust system disgusting itself as typical condensation fluid. Here is a link to a gentleman replacing the core on an expedition; process and location are likely similar.
Worth a check in this location to see if this is your problem. Hope this helps. Best of luck troubleshooting.