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Overheating at idle

nole99

Well-Known Member
Joined
February 15, 2003
Messages
105
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1
City, State
Phoenix Arizona
Year, Model & Trim Level
2001 Explorer Sport
Ok ... here's the dilly ... 2001 Explorer Sport 4.0 SOHC ... Just got the truck this week so not sure of maintenance history ... The Mounty was totaled thanks to some idiot w/out insurance who failed drivers ed!


For my work I make about 20 stops a day that last anywhere from 2-30 min in duration.

When I first start the truck in the morning the Check Gauges light comes on and lasts about a min before going off.

Temp is fine when driving ... then a few hours into the day if I am parked doing paperwork with the truck running the Temp Gauge starts to rise 3/4 to Hot ... as soon as I start driving it comes right back down to under half way up the Gauge.

It seems that after a few hours into the day ...If I leave the EX running at idle for anymore than 10 min the temp moves to 3/4 again ... When I drive ... it falls right back down ... when stopped at lights the temp seems to stay relatively constant ... doesn't shoot up real quick


A look under the hood revealed the following ...

Coolant level is OK
The upper hose on the radiator was collapsed last night but is now back to normal
Looks as though there is some minor seepage of coolant at the thermostat housing

My plan to start with

Flush
Replace Thermostat / Gasket
Replace Upper and Lower Radiator hoses

Does this seem reasonable?

When cutting the core hose to install the flush tee ... which one should I pick? Does it matter?


Thanks ... looks like I'll be around here a good bit again getting this rig in perfect order!
 



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i would say the lower hose and all the ideas sond like a good idea but you can check the therm by setting it in a pot of water the bringing it to boil if it doesent open by the time it boils then the therm is bad. but it already sounds that way. well good luck to you i hope it is that simple
 






Check the link im my signature for how to's on flushing the radiator and replacing the thermostat.

Usually the thermostat will fail open, which means the coolant circulates when it shouldnt. You might have the rare situation where it fails closed and the coolant cant circulate. When you drive the waterpump (assuming its working) is forcing the coolant through the thermostat housing bypass and cooling it enough to keep it from over heating.

After your do the flush (as mentioned in the video CLR works AMAZING) and replace the thermostat if it still over heats I would guess it is the water pump. Nothing else that it could be but a pinched hose or bad coolant.

Do yourself a favor and dont bother with the thermostat gasket just get a tube of RTV. Much easier to use, lasts longer, and seals better.
 






Dumb question for the day. Are the fans coming on during the stops and while overheating? I ran into a similar condition on a v-6 oldsmobile I was working on.
 






No such thing as a dumb question.

I believe most explorers (at least the older ones) use mechanical fans that run off of the crankshaft. You can do the electronic conversion to eliminate that though. It gives you a couple ponies and a little better gas mileage.
 






OK now I thinking. It was a dumb question. What I should have asked was with regard to the fan clutch. WHen hot, is the fan really locked up and turning fast. I'm not sure it's a flush issue. Concerning coolant flow, an engine idleing should be the least dependant on flow. Could be wrong though.
 






Thanks for the replies ....

Yes the fans is spinning while running and when spun by hand seems to spin freely without issue ... mechanical fan ... not electric

Therm stuck closed could be the issue ... hence the coolant seepage at the therm housing from being forced thru by the water pump

If the pump was failing wouldn't it overheat while driving as well??
 






The air movement could be enough to cool it.
 






Shouldn't there be resistance on the fan when spun by hand? That's what the clutch does. May depend on your definition of "freely". Fan should not just freewheel when spun by hand -

EE
 






You could also have a partially clogged radiator. I ended up replacing a motor once cause the mechanic told me it had a cracked head gasket which was causing it to heat up. After the motor was swapped, I had the same problem. I only ended paying for the motor and the radiator shop covered the labor for the engine swap and they also rodded out the radiator for free. Didn't have any problems after that.
 






Just wanted to post an update ... the problem seems to have been solved ... several hours later and a few trips to auto zone

Sooooo .... Therm was stuck closed ... yippee ... easy fix ... NOT so much!!!

For starters the damn brass sleeve in the rear of the thermostat housing has broken free from the plastic so it was just spinning ... I used my interion trim puller and was able the get the ******* out ... yeah


I then epoxied the brash sleeve back in and did my flush ... wasn't too dirty ... used one round of prestone flush then another round of clr ... let her fluch clear about 30 min to insure all contaminants an residual were clear

Put her back together and I'll be a son of of a pup if the housing that the therm and sensor sits in isn't leaking under pressure between where the bottom two layers of plastic seal ... at this point I am cursing the engineers at ford up and down for using a 3 piece plastic system

Long story short the bolts for that housing are a mother load to get to ... had to take off the alternator and a bunch of stuff ... I decided to replace the water pump while I had it all apart

The only negative was that part was 350 from the dealer ... it did include a thermostat, gasket, and both sensors ... and was all assembled

About 6 hours of time all together and the problem appears to be solved ... no leaks either :)

I am gonna do a full write up in the next week or so as I took a bunch of pics

Thanks again for the ideas!!!!!
 






Shouldn't there be resistance on the fan when spun by hand? That's what the clutch does. May depend on your definition of "freely". Fan should not just freewheel when spun by hand -

EE

Yeah there is a little drag ..... by freely I meant no grinding or hiccups or seizure
 






Glad you found it. Its VERY rare for a thermostat to seize closed but it does happen.

One thing that works well for next time is RTV each piece of the plastic together one at a time and wait 20-30 min for it to dry. Then move on to the next step ect...
 






Glad you found it. Its VERY rare for a thermostat to seize closed but it does happen.

One thing that works well for next time is RTV each piece of the plastic together one at a time and wait 20-30 min for it to dry. Then move on to the next step ect...

Yeah .... thats what I did when I put it all back together ... the housing part is actually 3 pieces fo plastic all bonded together from the factory ... there was no way to get it all apart and figure out what was what ...

I suspect what happened is someone previously used a bolt that was too long in that rear hole ... it doesn't go right thru like the 2 up front ... in doing so the forced the brass sleeve up out of its setting and in the process split the housing along the seams ... you could see the leakage in that area

Ahhh well ... Cooling system all new ... and got real personal with the SOHC
 






Good stuff. :)

I just had a disaster tonight with a 2001 ZX2 escort. Im going through the some bs. lol.
 






Usually the thermostat will fail open, which means the coolant circulates when it shouldnt. You might have the rare situation where it fails closed and the coolant cant circulate. When you drive the waterpump (assuming its working) is forcing the coolant through the thermostat housing bypass and cooling it enough to keep it from over heating.

I've had them fail both ways. No rhyme or reason to them.


Do yourself a favor and dont bother with the thermostat gasket just get a tube of RTV. Much easier to use, lasts longer, and seals better.
Not on an SOHC motor... the housing uses an o-ring, and the lower housing to block is an x-ring.


Good stuff. :)

I just had a disaster tonight with a 2001 ZX2 escort. Im going through the some bs. lol.

I assume it's leaking from the thermostat housing on a 2.0L Zetec motor?

Get a new housing. $66 at the dealership. I changed my sister's a week ago in the parking lot at the school where she teaches. Takes about an hour if you've got the tools (it took us two trips to the parts store because I forgot a couple of tools).
 






Good stuff. :)

I just had a disaster tonight with a 2001 ZX2 escort. Im going through the some bs. lol.

Hopefully a cooling disaster and not an uninsured illegal who can't drive :)

Well I worked again today and the darn truck started gettin up to 3/4 hot and would cool as I drove

Weird that I let it run for a good 30 min last night ... took her for a drive then let it sit another 30 min and the temp was steady just under half way up the guage

Looks like the only thing left to swap is the radiator ...

Soooo my question ... I have a 1 year old radiator in my mangled 5.0 mounty ... it is double row ... anyone ever use one in the 4.0 EX?

I hate this crap ... the AC condenser is ticking a weee bit too joy joy
 






Hopefully a cooling disaster and not an uninsured illegal who can't drive :)

Well I worked again today and the darn truck started gettin up to 3/4 hot and would cool as I drove

Weird that I let it run for a good 30 min last night ... took her for a drive then let it sit another 30 min and the temp was steady just under half way up the guage

Looks like the only thing left to swap is the radiator ...

Soooo my question ... I have a 1 year old radiator in my mangled 5.0 mounty ... it is double row ... anyone ever use one in the 4.0 EX?

I hate this crap ... the AC condenser is ticking a weee bit too joy joy
 






Hopefully a cooling disaster and not an uninsured illegal who can't drive :)

Well I worked again today and the darn truck started gettin up to 3/4 hot and would cool as I drove

Weird that I let it run for a good 30 min last night ... took her for a drive then let it sit another 30 min and the temp was steady just under half way up the guage

Looks like the only thing left to swap is the radiator ...

Soooo my question ... I have a 1 year old radiator in my mangled 5.0 mounty ... it is double row ... anyone ever use one in the 4.0 EX?

I hate this crap ... the AC condenser is ticking a weee bit too joy joy

Try starting it with the rad cap off when the truck is cold. Watch the coolant in the rad. When the thermostat opens the coolant should start to move and gush out the the top of the rad spout (make sure to clean it up...no one wants dead pets).

With the rad cap on and the engine warm and running, try squeezing the upper and lower rad hose (DO AT OWN RISK - FAN BLADE/BELT DANGER - USER BEWARE - NO TIES OR PIMP CHAINS HERE!!!). You should be able to feel how fast it refills and this can give you an idea as to the water pump condition.

If the water pump is the problem, the weep holes should be giving a sign on the ground. Otherwise it could be the rad is blocked. Many years ago I had this happen on one of my race cars and it took alot of searching before someone pulled the damn rad and put a light to it. Can't remember how we ran that day but I do remember alot of red faces...no light through the rad = no air through the rad = bad day = $ = lots of yelling. Funny how that works...
 



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Ok so after some tinkering and testing over the past 2 days I think the final piece to my puzzle is going to be the fan cluth and not the radiator based on the following

When the engine is hot or cold the resistance on the fan when spinning by hand does not change

After doing the whole block the radiator with cardboard and listen for the fan clutch to engage ... all I got were crickets

Then did the whole fan RPM test and unless I did the test wrong ... there was no engaging of the clutch

What I did notice tho were 2 things

If I don't run the AC at all the temp gauge would barely even go over half while driviing and sitting for 10 to 15 min today as soon as I turn the AC on within 5 min the temp would shoot right up due to increased RPM most likely

Also if I just let it run in my garage with the hood up ... the temp would never go above half with the AC on

So once the beast cools a bit I shall install the new fan clutch I just picked up and report back!!!
 






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