4.0 SOHC cooling system puzzler...

[Robman]

Indeed... take a gulp and no air can flow out which is displaced and vented by the new incoming fluid.

Take a sip and you get a free and even exchange through the same channel of both.
I know, it's an obvious thing, haha.. I just felt like typing.

 

[MillerAPF97XLT]

Thanks again, koda. Yeah, Stant does have a 190degree stat in addition to the lower-temp unit. O'Reilly is the only local store here in town, and, yes, Murray and Motorcraft are the two brands of thermostat they show. Here's the latest - After topping up the radiator this morning (maybe 3 quarts), I started the truck, let it idle and watched the gauge. After about 10 minutes, the needle parked just below the middle of the gauge again. Cold air from defroster and floor registers. Maybe 5 minutes later, needle went to just below red, Check Gage light came on, idle went from about 700 to 1200, and warm air started to flow. Less than a minute later, the needle went toward cool, light went out, idle came back down and warm air continued. Another 4-5 minutes later, the needle went to about 3/4, and the idle came up some. Temp then went right back down along with the idle. For the next 20 minutes, the needle and idle speed never moved. Going to let it cool, check coolant level, let it warm up through the 2-step, and take it on the road for a bit. I'm leaning toward thermostat issues. I want to stay with the OEM temp, but I don't want to have to watch the gauge go crazy. If it didn't do that when it left the dealer's lot, it shouldn't be doing it now. Thanks again to all. More in a bit. - Chris

 

[rathrbcruisin]

Something that I've always done is to let it run with the radiator cap off. who cares if coolant comes out the top, you need to get that air out. Let it run and squeeze the hoses to try to get that air out. I'm sure there is air in there.

 

[MillerAPF97XLT]

Thanks, 'cruisin. I had thought about that, don't know why I hadn't tried it. However, I may finally be on to something. If there's a leak in the system, it won't pull coolant out of the recovery tank as the system cools, right? Well, after plenty of time to cool down (hoses and radiator were outside air temperature), the recovery tank was as full as it was when I shut the engine off. AND, I heard what could have been mistaken for a trickle in the area of the thermostat housing, but it would slow down and stop as I applied squeezage to the upper radiator hose. Bet the lower pressure in the system is pulling air IN past a leak that's just not quite big enough to let coolant OUT, or some such BS. I suspect a breach in the plastic (UGH!) 'stat housing. Anyone? Bueller? At least I think I've found an answer to why the radiator is always low... Still welcome any/all input. - Chris

 

[koda2000]

Thanks, 'cruisin. I had thought about that, don't know why I hadn't tried it. However, I may finally be on to something. If there's a leak in the system, it won't pull coolant out of the recovery tank as the system cools, right? Well, after plenty of time to cool down (hoses and radiator were outside air temperature), the recovery tank was as full as it was when I shut the engine off. AND, I heard what could have been mistaken for a trickle in the area of the thermostat housing, but it would slow down and stop as I applied squeezage to the upper radiator hose. Bet the lower pressure in the system is pulling air IN past a leak that's just not quite big enough to let coolant OUT, or some such BS. I suspect a breach in the plastic (UGH!) 'stat housing. Anyone? Bueller? At least I think I've found an answer to why the radiator is always low... Still welcome any/all input. - Chris

You are correct in thinking that if you have a coolant leak it wont draw from the expansion tank. I had this happen in several of my trucks when the radiator side tank seals were leaking. It was easier for the cooling system to suck in air through the seal than to get it from the expansion tank. With the system working properly, I see about a 1" difference in the expansion tank coolant level between a stone cold and warmed up engine. It's also fairly common for the hose leading to the expansion tank to be clogged or too loose. You can try blowing through it to see if it's clogged and check to make sure it's making a good tight connection at the radiator and the expansion tank. If in doubt, replace the hose.

Don't obsess about the TEMP gauge. It's not really a gauge and will always read in about the center as long as your water temp is w/in a range (maybe between 167-200 degrees F). Wide fluctuations in the needle are usually due to a bad t-stat.

 

[MillerAPF97XLT]

Thanks, koda. The tank hose could be a tad loose on the nipple at the filler neck. It doesn't offer much resistance to being pulled off. It IS clear, though; it flowed coolant real good when I used gravity to recover coolant out of the tank through the hose yesterday. As for the gauge, I'm hoping it will start to behave better once the rest of the system is working right. I'll worry about it a whole lot less when there's no light telling me to check it! Side note - I tested the operation of the old 'stat earlier this afternoon - started to open around 180, wide open about 195. But the budget replacement is giving the same behavior as the original, so I'm not sure it was ever the thermostat at all. At the least, maybe the 'stat wasn't the primary problem. Now to find the source of the leak. Kinda weird that it wouldn't pass coolant, though. Okay, that's enough rambling. 'Til I have more news,... - Chris:exp:

 

[koda2000]

Thanks, koda. The tank hose could be a tad loose on the nipple at the filler neck. It doesn't offer much resistance to being pulled off. It IS clear, though; it flowed coolant real good when I used gravity to recover coolant out of the tank through the hose yesterday. As for the gauge, I'm hoping it will start to behave better once the rest of the system is working right. I'll worry about it a whole lot less when there's no light telling me to check it! Side note - I tested the operation of the old 'stat earlier this afternoon - started to open around 180, wide open about 195. But the budget replacement is giving the same behavior as the original, so I'm not sure it was ever the thermostat at all. At the least, maybe the 'stat wasn't the primary problem. Now to find the source of the leak. Kinda weird that it wouldn't pass coolant, though. Okay, that's enough rambling. 'Til I have more news,... - Chris:exp:

These radiators usually tend to leak from the plastic tank seals. It might be hard to see from where with the rad still in the truck. Look for dried green residue on the black plastic side tanks. If you drop the plastic cover under the rad, there may be coolant in it. I just removed the radiator from my '01 ST on Sat. Should have a replacement rad here by Wed-Thru. I find that if the tank seals are leaking near the top of the radiator the coolant level may only drop a little and then stop leaking, but the quantity on the expansion tank remains unchanged, as it sucks air in thru the seal. My tank seal blew out on the lower part of the side tank, so it puked out almost all the coolant and drained the expansion tank.

 

[MillerAPF97XLT]

I really don't think it's losing coolant anywhere. Weird, since it does have a problem holding pressure. But I have never smelled but just a whiff of coolant, and haven't seen any anywhere. I've seen the plastic-tank radiators leak at the tank gaskets, and also make the plastic brittle at the upper hose neck and leak there. Whoever dreamed up making cooling system parts out of plastic must be in the business of selling replacement plastic cooling system parts.

 

[XLTrunner]

It's not necessarily true that if you have a coolant leak it won't pull coolant from the recovery tank. I just went thru this with my leaking t-stat housing (twice this past summer) and believe me, it was sucking everything and more out of the recovery tank and radiator. I put up with this for weeks until I could find the time to change it out (twice as the new, cheap-ass Four Season housing started leaking 2 wks after I installed it)...and, went thru several gallons of coolant in that time. Never did I have any problem with the t-stat, heating/cooling or temp gauge acting up during that time. And, when it came time to replace it, I simply filled the radiator and overflow reservoir, let the engine run with the cap off and all air bubbled out once it warmed up. Topped it all off once it was driven and cooled down, again. It's all good, now. Easy...peasy.

 

[MillerAPF97XLT]

I see what you're saying, 'runner. Still, if it's easier to pull air back in through the leak as it cools than to overcome the seal of the pressure cap and re-fill from the recovery tank, the whole "least resistance" thing comes into play. That said, I can see where there could be instances where coolant would leak out under heat and pressure, then seal up enough to pull from the tank on the cool-down. Strange animals, these internal combustion engines... BTW, thanks for the heads-up on Four Seasons' housings. I'll be steering clear of them if I have to replace mine. - Chris:exp:

 

[MillerAPF97XLT]

Think I found the leak - spent the day pulling the t-'stat housing and saw the crusty build-up UNDER the housing, where the little o-ring seals it to the intake/head/block/whatevs. The o-ring itself is FLAT, flush with the bottom of the housing. Can't see how it was sealing at all. I've cleaned the housing and given it a preliminary inspection; looks good so far, but I'm not done looking for trouble on it. Think I want to replace the 'stat with a quality name-brand one (Stant!), BOTH o-rings, and all three hoses, just because I don't want to pull this back apart anytime soon. I really would like to stay with the OE 190-degree 'stat, but after what I've seen happening, the lower temp unit has some appeal as well. What's it going to hurt? It'll still get warm enough to let the ECM go into closed loop, won't it? And, should I replace the temp senders while I'm at it? Or can I test them to see if they're within spec? Wow. I thought the hard work would be getting the stuff off and back on, not the decision-making process.Once again, any/all input... TIA - Chris

 

[swshawaii]

There is a very high probability the lower t-stat housing is splitting it's seams. Extremely common issue and the most commonly failed cooling system part on ALL 4.0L SOHC's. Earlier models also have threaded sensors with brass inserts that usually fracture the plastic housing when attempting to loosen. Consider the upgraded RH144 housing with newer sensors linked below if your lower housing needs replacing. Regarding the lower temp t-stat, most here strongly advise against it due to condensation and sludge issues caused by slow engine warm up, not to mention reduced MPG. Search.

See posts #3 and #4
http://www.explorerforum.com/forums/showthread.php?t=345845

 

[XLTrunner]

There is a very high probability the lower t-stat housing is splitting it's seams. Extremely common issue and the most commonly failed cooling system part on ALL 4.0L SOHC's. Earlier models also have threaded sensors with brass inserts that usually fracture the plastic housing when attempting to loosen. Consider the upgraded RH144 housing with newer sensors linked below if your lower housing needs replacing. Regarding the lower temp t-stat, most here strongly advise against it due to condensation and sludge issues caused by slow engine warm up, not to mention reduced MPG. Search.

X2! The ECT sensor will usually unscrew...but, the Temp Sensor retaining nut is molded into the plastic housing (rather poorly, I might add) and I guarantee you it will just spin if you try to unscrew that one. Then, you've probably just introduced another leakage point. Go with the RH144 upgrade as suggested.

 

[MillerAPF97XLT]

Cool! I'm all about swapping out for newer and better parts. I mean, heck, even if this truck is not destined to be a hot-rod rock crawling monster, I still want to be able to start and drive it anywhere, anytime. So, the RH144 is a straight-up swap, no more required?

 

[XLTrunner]

Here's your parts list. I purchased everything listed but the clips (got those at the local Pick-N-Pull) from Rockauto for about $85 shipped.

- RH144 Motorcraft lower housing
- Reuse your existing upper housing (assuming it's in good shape)
- RG614 Lower housing to engine seal
- SW6146 Temp gauge sensor
- DY1004 ECT sensor

You'll need the retaining clips for the sensors.

- Ford #W706800-s303
- Dorman #800-019
- NAPA #NOE7305034

 

[MillerAPF97XLT]

'Runner, you the man! I was just getting back on here to poll about preferred brands and sources. If not going with OEM, I like Dorman for a lot of stuff. And RockAuto has never disappointed. So, when I order, do i look up an '02-up Explorer to get me there?

 

[swshawaii]

Would likely find Dorman parts in the bottom 10% if you ran a poll here. :thumbdwn: JMO

Among MANY others, XLTrunner has BTDT. Motorcraft FTW.
https://www.explorerforum.com/forums/showpost.php?p=3484740&postcount=3

 

[XLTrunner]

I believe that is how I did it. PLEASE, PLEASE do not give in to the temptation to buy either the Four Seasons (which I've read is a Division of Dorman) or the Dorman brand of t-stat housings. I've already told you about my experience with the Four Seasons brand. And, posted results from others are that Dorman's are hit or miss. Go with the Motorcraft and be done with it...unless you get your jollys doing and re-doing this job. You're kind of where I was at with the thermostat issue. I had bought an off-brand t-stat at O'Reilly (only one they stocked) for my first attempt at changing the housing. Figured second time around, I'd go with a name brand (went with a Motorad) for peace of mind.

 

[jmvb]

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[acrx7]

Thanks, dubbio. I opened the drain on the radiator and when I got the housing off, there was no coolant left to splash all over everything. Hey - did I maybe not bleed the air from the system correctly? I know some engines are finicky about how you purge air from their cooling systems. Does the 4.0 SOHC have a particular procedure?

Hi there MillerAPF97XLT , don't forget about the heater core , most people forget to have the heat knob to the hottest setting so it can circulate what is in the heater core and also to be bleed