4.0L Coolant Temp Spiking with A/C

[94Eddie]

Bit of an update, if anyone is interested. I went ahead and bought some rad flush and distilled water, about 10 gallons, along with new coolant. Was going to do the flush one day and saw a pretty consistent leak under the truck. Upon further inspection I saw a steady drip coming from what I now know is the water pump. Whether it's from the weep hole, or a failed seal I'm not sure, but after doing some digging it makes sense it would be a water pump problem. The area below it and is CAKED in black sludge, a combination of coolant and dirt I'm sure. So I'm going to be ordering a new water pump, and fan clutch and doing it myself along with some help from my dad. Of course, I'll also get a new belt while I'm in there. Wanted to see if anyone recommended changing anything else while I'm doing all this. I'll still do a flush, but after I have the new pump in, to make sure the radiator is all good. Fingers crossed I'll have no more problems after this!

I would recommend changing the upper and lower hoses and thermostat if they are original.

 

[ARC95]

I would recommend changing the upper and lower hoses and thermostat if they are original.

Are those the same size? Currently looking on rockauto for parts.

 

[94Eddie]

Are those the same size? Currently looking on rockauto for parts.

I am not very familiar with 4.0L SOHC engines. I recommend following what Rock Auto says for the parts.

 

[ARC95]

Check your fan blade for cracks if it has any cracks replace it asap also severe duty fan clutches in my experience are better than factory but i believe yours is all electric so your results may vary mines a 99

I'll probably stick with a motorcraft one, this one lasted 13 years haha. And good advice for the blades, I'll be sure to check those!

 

[Lee's Automotive]

I'll probably stick with a motorcraft one, this one lasted 13 years haha. And good advice for the blades, I'll be sure to check those!

Yep stick with motorcraft if it's electric

 

[Blackhawkxx]

Like was said, the hoses is a good idea. If you don't have the money to do both, get the bottom one as it is so much harder to get to when everything is back together. While you are there, take a peek at the harmonic balancer to make sure nothing is separating. Mine went at about 100K.

 

[ARC95]

Like was said, the hoses is a good idea. If you don't have the money to do both, get the bottom one as it is so much harder to get to when everything is back together. While you are there, take a peek at the harmonic balancer to make sure nothing is separating. Mine went at about 100K.

Ordered a top and bottom hose already. Yeah, I'll need to check the H. Balancer. If it's on it way out, and I'm already taking the belt and fan clutch and all that stuff off, it's worth it just to do it then so I don't have to take all the crap off again. Thanks for the tip!

 

[donalds]

Leave the harmonic balancer alone unless it is messed up if you are suspicious take a paint marker and draw a line across the front of the balancer if it separates the line will move

 

[ARC95]

Little update, as I know someone was saying there were having a similar problem: Just did a prestone cooling system flush and ran it for about 30 mins or so. Noticed some what look like calcium or minerals at the top of the radiator just under the cap when I was about to fill with the flush and distilled water. Once while running had a huge plume of whitish gunk come up to the top and "burp" before the level went back down. Didn't notice anything that would indicate a head gasket so I'm happy about that. Temp stayed around 190F, which was without moving so I'm sure the water pump/fan clutch is the culprit like what you guys were saying, being put under load would probably make it overheat while driving. Still waiting on parts, hoping to get my water pump here soon. Once I do the install I'll let you know know how it goes. Also thanks for the tip donalds, I'll be sure to mark it, should have done it before doing the flush! D'oh! Also noticed some coolant in the flat area behind the Thermostat housing, probably leaking from the housing(?) too as I didn't torque to spec when I put it on (don't hate me, after that I bought a torque wrench).

 

[94Eddie]

Little update, as I know someone was saying there were having a similar problem: Just did a prestone cooling system flush and ran it for about 30 mins or so. Noticed some what look like calcium or minerals at the top of the radiator just under the cap when I was about to fill with the flush and distilled water. Once while running had a huge plume of whitish gunk come up to the top and "burp" before the level went back down. Didn't notice anything that would indicate a head gasket so I'm happy about that. Temp stayed around 190F, which was without moving so I'm sure the water pump/fan clutch is the culprit like what you guys were saying, being put under load would probably make it overheat while driving. Still waiting on parts, hoping to get my water pump here soon. Once I do the install I'll let you know know how it goes. Also thanks for the tip donalds, I'll be sure to mark it, should have done it before doing the flush! D'oh! Also noticed some coolant in the flat area behind the Thermostat housing, probably leaking from the housing(?) too as I didn't torque to spec when I put it on (don't hate me, after that I bought a torque wrench).

If you saw mineral buildup in the radiator then this would indicate the overheating is due to a blockage caused by mineral buildup. If chunks are floating around in the radiator it most likely means the cross passages are clogged and/or partially clogged too. Nearly everything you have found so far tells me the overheating is due to a coolant flow issue and not the fan clutch going bad. When you have the coolant drained out, look into the radiator with a flashlight and see if you can see a buildup of minerals. You could do all this work and find you still have an overheating problem. Once the flush is done then fill it with water, drive it and see if this helped reduce or eliminate the problem.

 

[ARC95]

If you saw mineral buildup in the radiator then this would indicate the overheating is due to a blockage caused by mineral buildup. If chunks are floating around in the radiator it most likely means the cross passages are clogged and/or partially clogged too. Nearly everything you have found so far tells me the overheating is due to a coolant flow issue and not the fan clutch going bad. When you have the coolant drained out, look into the radiator with a flashlight and see if you can see a buildup of minerals. You could do all this work and find you still have an overheating problem. Once the flush is done then fill it with water, drive it and see if this helped reduce or eliminate the problem.

Honestly, I think it's both the water pump leaking, which I would assume was first, and the mineral build up in the radiator. Like I said before, I just bought this truck and haven't driven it hardly at all before having to deal with all this. My hypothesis is that the water pump starting leaking for the previous owner, they tried replacing the therm. housing with a cheapo plastic one thinking it was that and continued to leak. Then they added tap water to keep the rad topped off, causing mineral build up. Then they said screw it, traded the thing in, and now I have the overheating problem from the mineral build up, in tandem with a failing water pump. The fan clutch I'm replacing because, knowing my luck if I don't, 500 miles from now my fan clutch would go and I'd be ripping it off to replace it. I really pray that doing a somewhat thorough replacement of these parts and my first flush will help. I still have a second bottle of flush if when I take the distilled water and flush out it's disgusting, and I'll keep you guys posted as to how it looks.

 

[ARC95]

If you saw mineral buildup in the radiator then this would indicate the overheating is due to a blockage caused by mineral buildup. If chunks are floating around in the radiator it most likely means the cross passages are clogged and/or partially clogged too. Nearly everything you have found so far tells me the overheating is due to a coolant flow issue and not the fan clutch going bad. When you have the coolant drained out, look into the radiator with a flashlight and see if you can see a buildup of minerals. You could do all this work and find you still have an overheating problem. Once the flush is done then fill it with water, drive it and see if this helped reduce or eliminate the problem.

I did a second flush and drove a bit today. When I drained the first bottle of flush there was still some coolant with it, which really shouldn't have been there if I drained it fully. I also saw a bit of coolant bubble up as I was adding water during the second flush when running. I think you were right, for the overheating problem it was a blockage from mineral build up. I'm going to drive it with the flush in this week, just flush and distilled water. The prestone flush I'm using says you can do a "heavy duty flush" by driving for 3-6 hours. Once that's done I'll see how the water looks coming out. I'm still going to replace the water pump and fan clutch, as I think the water pump will still be leaking, and I want it all to be done with! The highest temp I got during my 30 or so mins of running while adding water and the 15-20 mins of driving was 203 F, it hovered around 192-198 mostly. I'm hoping this is a good sign! Also went ahead and ordered a 16 psi cap, Motorcraft RS76 on amazon, hoping this all helps fix this crap.

 

[Blackhawkxx]

Also went ahead and ordered a 16 psi cap, Motorcraft RS76 on amazon, hoping this all helps fix this crap.

The 16 lb cap won't lower your temp but may help prevent leaks.

 

[ARC95]

The 16 lb cap won't lower your temp but may help prevent leaks.

Ah yes, sorry I didn't mean to have it sound like that. I ordered the 16 psi cap to prevent leaks like you said. I know a lot of guys here have said they ran it with no problems. I want to have the water pump and all that jazz all run as long as possible so I don't have to do this all again! Thank you for mentioning that however, I should have been more clear. I also ordered a 20lb cap to throw in the glove box in case something goes awry with the 16lb cap! I'm hoping to have more good news after some more drives!

 

[ARC95]

Late with an update but with good news! So, I swapped the radiator, rad cap with a 16psi, water pump, fan clutch, idler pulley, rad hoses, and belt on the explorer. I also took that opportunity to do a partial transmission flush and change it's filter and clean the pan. I'm now over 400 miles since doing it all and she's been running strong! Set to get some new tires put on this weekend and she should be all good to go for the winter. Only other thing I'd want to look into is getting a preoiler as living in Wisconsin it can get quite cold. I would still say for my overheating problem it was a combo of the radiator being shot and the water pump being shot. The radiator had some quite gross corrosion on the inner side that we didn't see until taking the fan off, and the water pump was leaking and most likely didn't have a good enough flow. If someone is on a budget and having this problem they should for sure inspect the radiator as much as possible and see any points where it could be leaking/bad and check the water pump for leakage. Thank you everyone for the help so far