Redid the cooling system... Temperature weirdness now...

[DP96XLT]

This is for a 1996 Explorer 4dr 4wd 4.0l OHV v6 with 44k miles on it.

Ok, so I went through, pulled everything and put in the following new equipment:

- Radiator (Spectra Premium)
- Waterpump (Airtex)
- Thermostat - 198 degree (Motorad UltraStat)
- Thermostat Housing (Dorman)
- All new molded hoses (Dayco)
- Heater core 5/8" hoses (Gates)
- Heater Valve (Four Seasons)


I bled the system per the instructions in the 1996 manual (having the radiator cap on pressure release, running at fast idle, 2000rpm, etc).

The issue I am having is that the system seems to have trapped air, as the temp gauge goes up to the "normal" area about 1/4 up the gauge, then it will climb to the middle (where the water temp symbol is) and then the thermostat will eventually open and it swings upwards a little and then goes back down to near the vertical line near the "C" mark on the gauge... As it heats up again it does the same cycle.

I did notice if I turn the heat in the car off, it is much more stable and doesn't swing as wildly, but it is far from "stable" the way most cars are... Before doing all this stuff it was acting as if the thermostat was stuck slightly open, but in retrospect I can't tell after pulling the thermostat which thermostat it is, as the only marking are a "52mm" on the outer ring, a 1/8" at most hole without a valve (supposed to go up upon install), the bottom has a 1013 195 marking and a STC stamped on the lower bridge. Does this sound like a Stant Superstat? It does have a larger thermostat opening with three "V" cuts around the perimeter of the area that lowers to open the thermostat.

Now, to rectify this swing (as it seems as if there is air trapped in the system somewhere), I waited until it was cold, then pulled the heater hoses near the firewall off the heater valve and both lines are full. The valve is full to the lines, so it would seem there is no air trapped in the heater core or in the bypass lines, so why would there be such a bigger swing with the heat on (blower on low) than with the heat off?

I also went out and picked up a coolant funnel kit with the fittings to fit on top of the radiator fill neck. I ran it like this and minimal bubbles came out. I then, while it was still running, jacked up the front end as high as my high-lift jack would go (basically the panel in front of the radiator was planed out horizontally looking at it from the side) and got a few more bubbles, but nothing I would figure would explain the drastic swing. While doing this I did it while idling, while running at 2000rpm, 2500rpm and 3000rpm for a few cycles to see if I could get trapped air out. I will add that I did notice some "hammering" via the upper radiator hose when I first started doing this procedure and noticed none when I was done, so I am "somewhat" hopeful that I was able to get all of the air out.

After all that I shut it down, waited a bit, removed the funnel and put the cap back on... I will wait until it is totally cool and then add more fluid to the overflow reservoir to bring it up to the "Full Cold" mark. I just can't see it being that much that came up and through the funnel, unless after it cools I noticed a considerable amount of coolant lower in the radiator itself.

I still can't understand why it would pressurize so much, then have the thermostat open, drop the pressure to minimal when it gets cold water from the radiator and then recycle as drastically. Seems like a really poor design to do that much of a swing. I will admit that before redoing the cooling system I just figured it wasn't getting up to temp (185-190 on the scantool, sometimes dropping down to 180 on the freeway in the really cold weather), and that it needed a new thermostat.

One phenomenon I noticed before doing the funnel-bleed is that it would push a decent amount of coolant into the overflow at high pressure, then it would collapse the upper radiator hose while it tried sucking a good amount of coolant back into the system from the overflow. That would mean to me a decent amount of air is trapped. I saw nothing like that come out of the funneled setup earlier today.

Also, I was not losing any coolant before the system redo, and I do not believe I am losing any now.

 

[96eb96]

This is for a 1996 Explorer 4dr 4wd 4.0l OHV v6 with 44k miles on it.

Ok, so I went through, pulled everything and put in the following new equipment:

- Radiator (Spectra Premium)
- Waterpump (Airtex)
- Thermostat - 198 degree (Motorad UltraStat)
- Thermostat Housing (Dorman)
- All new molded hoses (Dayco)
- Heater core 5/8" hoses (Gates)
- Heater Valve (Four Seasons)


I bled the system per the instructions in the 1996 manual (having the radiator cap on pressure release, running at fast idle, 2000rpm, etc).

The issue I am having is that the system seems to have trapped air, as the temp gauge goes up to the "normal" area about 1/4 up the gauge, then it will climb to the middle (where the water temp symbol is) and then the thermostat will eventually open and it swings upwards a little and then goes back down to near the vertical line near the "C" mark on the gauge... As it heats up again it does the same cycle.

I did notice if I turn the heat in the car off, it is much more stable and doesn't swing as wildly, but it is far from "stable" the way most cars are... Before doing all this stuff it was acting as if the thermostat was stuck slightly open, but in retrospect I can't tell after pulling the thermostat which thermostat it is, as the only marking are a "52mm" on the outer ring, a 1/8" at most hole without a valve (supposed to go up upon install), the bottom has a 1013 195 marking and a STC stamped on the lower bridge. Does this sound like a Stant Superstat? It does have a larger thermostat opening with three "V" cuts around the perimeter of the area that lowers to open the thermostat.

Now, to rectify this swing (as it seems as if there is air trapped in the system somewhere), I waited until it was cold, then pulled the heater hoses near the firewall off the heater valve and both lines are full. The valve is full to the lines, so it would seem there is no air trapped in the heater core or in the bypass lines, so why would there be such a bigger swing with the heat on (blower on low) than with the heat off?

I also went out and picked up a coolant funnel kit with the fittings to fit on top of the radiator fill neck. I ran it like this and minimal bubbles came out. I then, while it was still running, jacked up the front end as high as my high-lift jack would go (basically the panel in front of the radiator was planed out horizontally looking at it from the side) and got a few more bubbles, but nothing I would figure would explain the drastic swing. While doing this I did it while idling, while running at 2000rpm, 2500rpm and 3000rpm for a few cycles to see if I could get trapped air out. I will add that I did notice some "hammering" via the upper radiator hose when I first started doing this procedure and noticed none when I was done, so I am "somewhat" hopeful that I was able to get all of the air out.

After all that I shut it down, waited a bit, removed the funnel and put the cap back on... I will wait until it is totally cool and then add more fluid to the overflow reservoir to bring it up to the "Full Cold" mark. I just can't see it being that much that came up and through the funnel, unless after it cools I noticed a considerable amount of coolant lower in the radiator itself.

I still can't understand why it would pressurize so much, then have the thermostat open, drop the pressure to minimal when it gets cold water from the radiator and then recycle as drastically. Seems like a really poor design to do that much of a swing. I will admit that before redoing the cooling system I just figured it wasn't getting up to temp (185-190 on the scantool, sometimes dropping down to 180 on the freeway in the really cold weather), and that it needed a new thermostat.

One phenomenon I noticed before doing the funnel-bleed is that it would push a decent amount of coolant into the overflow at high pressure, then it would collapse the upper radiator hose while it tried sucking a good amount of coolant back into the system from the overflow. That would mean to me a decent amount of air is trapped. I saw nothing like that come out of the funneled setup earlier today.

Also, I was not losing any coolant before the system redo, and I do not believe I am losing any now.

This is the nature of the beast with this engine. There is a known issue with steam formation. That may contribute to the heads cracking (pretty common issue). Even the owners manual tells you the coolant may drop a bit in up to 7500!!! miles. There may be some small air pocket. Maybe try one of those suction venturi coolant bleeders (you need a compressor).

Notice there is no bypass hose. It is internal in the intake manifold I believe. And very low volume.

There was a TSB ages ago with a special modified hose. I think it went from the lower coolant hose, with a T, to a T at the temp sensor. Others have connected the two heater hoses together with a bridge. It does not seem to affect heat.
The issues were gauge fluctuation or banging noises in the system.

Mine always had the temp gauge move around (never overheat though). The scan tool would mirror the trend.

I would use a Ford Thermostat though for this engine. At 44k I wouldn't worry about it. There are many cases of 200K+ engines going strong.

 

[DP96XLT]

Well, a little followup here...

Turns out I picked up a vacuum bleeder system (two of them actually) and drained and bled the system a total of three times (four times if you count the one time I did the heater core by itself) and still have the exact same issue.

Considering that using vacuum bleeders are how the factory fills cooling systems (but I figure they use a much higher vacuum, as I can get to 25" of vacuum as a maximum and I think they are around 30"+) I am sure that these systems leave the factory without any coolant weirdness (such as loosing coolant up to 7500 miles, or thumping/steam formation) there is something wrong with either the thermostat or waterpump.

I ended up disconnecting the coolant lines to the heater core (I was concerned about two things, one being a air pocket in the heater core, or a plugged core, regardless of the low miles and limited use) and back-flushed and forward-flushed the core with everything going into a standing tub and found virtually nothing coming out (on the back-flush I saw a small bit of black scale, which ultimately seemed like almost rubber flashing from hoses (basically what you would expect from a rubber hose that got a little bit of the inside shaved off when putting it on a metal hose barb that was sharp, ie, nothing to be concerned about) and definitely wasn't enough to plug anything up. It also had excellent flow through the core (verified via both the flushing as well as using pressurized air to blast out the water used to flush it). I also vacuum filled the heater core and verified it had no trapped air as well, all to no avail as the exact same problem existed.

So, I said screw the aftermarket parts, ended up placing an order a few days ago for all new Motorcraft waterpump, Motorcraft thermostat, Motorcraft upper heater hose (which was the only non-factory hose I couldn't get locally that was originally a molded hose that I ended up replacing with a 5/8" straight hose) and Motorcraft heat valve (yeah, I know it isn't the problem, but considering it was the only non-Motorcraft part in the entire cooling system, I figured I might as well be thorough for the $18 it costs).

I do believe I will add in a bleeder valve to the top of the thermostat housing as a "just in case", but I was successful with loosening the temperature sender in that housing to purge air bubbles, but to no avail.

I forgot to order a Motorcraft radiator cap, and will call around this morning to see if I can get one locally. All of the local auto parts stores (Autozone, Advance Auto, Oreilly Auto and Napa) all carry only the Motorad caps and I tried two of those with the same results.

Ultimately I believe the thermostat and/or waterpump are the culprits here. I *may* try the Motorcraft thermostat first and if that fixes it I will just put the rest of the stuff on the shelf as spares.

 

[fast_dave]

@DP96XLT


Lots of info in your two posts, but just askin'

When you're burping/bleeding the cooliong system "radiator cap on pressure release, running at fast idle, 2000rpm, etc." are you also:

* Turning the heater on into the red zone (aka full blast)

*Elevating the front end of the truck

If not, try adding those two procedures as they're proven and cost $0.00

Hope that helps and report back!

 

[96eb96]

Well, a little followup here...

Turns out I picked up a vacuum bleeder system (two of them actually) and drained and bled the system a total of three times (four times if you count the one time I did the heater core by itself) and still have the exact same issue.

Considering that using vacuum bleeders are how the factory fills cooling systems (but I figure they use a much higher vacuum, as I can get to 25" of vacuum as a maximum and I think they are around 30"+) I am sure that these systems leave the factory without any coolant weirdness (such as loosing coolant up to 7500 miles, or thumping/steam formation) there is something wrong with either the thermostat or waterpump.

I ended up disconnecting the coolant lines to the heater core (I was concerned about two things, one being a air pocket in the heater core, or a plugged core, regardless of the low miles and limited use) and back-flushed and forward-flushed the core with everything going into a standing tub and found virtually nothing coming out (on the back-flush I saw a small bit of black scale, which ultimately seemed like almost rubber flashing from hoses (basically what you would expect from a rubber hose that got a little bit of the inside shaved off when putting it on a metal hose barb that was sharp, ie, nothing to be concerned about) and definitely wasn't enough to plug anything up. It also had excellent flow through the core (verified via both the flushing as well as using pressurized air to blast out the water used to flush it). I also vacuum filled the heater core and verified it had no trapped air as well, all to no avail as the exact same problem existed.

So, I said screw the aftermarket parts, ended up placing an order a few days ago for all new Motorcraft waterpump, Motorcraft thermostat, Motorcraft upper heater hose (which was the only non-factory hose I couldn't get locally that was originally a molded hose that I ended up replacing with a 5/8" straight hose) and Motorcraft heat valve (yeah, I know it isn't the problem, but considering it was the only non-Motorcraft part in the entire cooling system, I figured I might as well be thorough for the $18 it costs).

I do believe I will add in a bleeder valve to the top of the thermostat housing as a "just in case", but I was successful with loosening the temperature sender in that housing to purge air bubbles, but to no avail.

I forgot to order a Motorcraft radiator cap, and will call around this morning to see if I can get one locally. All of the local auto parts stores (Autozone, Advance Auto, Oreilly Auto and Napa) all carry only the Motorad caps and I tried two of those with the same results.

Ultimately I believe the thermostat and/or waterpump are the culprits here. I *may* try the Motorcraft thermostat first and if that fixes it I will just put the rest of the stuff on the shelf as spares.

Run the truck and see if water is forced out of the radiator. There could be a hairline crack in the head. I have K-seal, no problems otherwise.

 

[DP96XLT]

Run the truck and see if water is forced out of the radiator. There could be a hairline crack in the head. I have K-seal, no problems otherwise.

I have and there is no coolant pushed out or lost...

It is almost as if the thermostat is short-cycling and as such it won't open until well above "boiling". and once it does it gets cold-shocked back down and it basically creates suction (ie, when it boils, it creates too much pressure which forces coolant out the radiator into the overflow, then it gets cold shocked back down which reduces the volume and it sucks the coolant back out the overflow).

I tested and there is no exhaust in the coolant and there are no air being pushed into the coolant. There is zero coolant loss and in general I think the problem is a bad thermostat.

I should have the Motorcraft OEM thermostat tomorrow and I will put it in right away and re-bleed the cooling system. If that doesn't work I should have the waterpump and the rest of the stuff within another day or two and will just redo it all then.

I would have to believe it is a matter of either out of spec parts or wrong applications. If I put in all Motorcraft stuff and it does the same thing I am at a complete loss. I have dealt with difficult to bleed cooling systems before, but not one that would cause issues like this.

It almost seems like a wayyyy oversized cooling system that can't stabilize. After a point you get so much heat out of the engine and coolant back in that the thermostat stays at a given temp give or take the load being applied. This is acting like it can't reach that level of equilibrium. Might be as simple as a badly spec'd thermostat for the application.

 

[Mbrooks420]

Isn’t that t-stat a little hot? It’s very possible it’s bad.

Other than that, I agree get the front end high as possible and run it up to temp with the radiator open.

Have to do the same thing with my Subarus, except you have to get the drivers side up high. Otherwise it just won’t purge.

 

[DP96XLT]

Yeah, I am highly suspect of the thermostat as well...

Before I got the vacuum fillers I did get the front end as high as possible (so high the header panel in front of the radiator was planed out horizontal when looked at from the side) and made sure it burped with a funnel-coolant-fill system (had that adjsuted with 2 45-degree adapters extremely high as well, and on an angle to match)...

That is why I am actually quite pissed at this point... This stuff should not be that difficult.

I will put in the Motorcraft thermostat and do a full vacuum bleed on it. I have a funny feeling it will work right off the bat.

If so, great. If not, then the rest of the parts go in. Since if it is the thermostat then the rest will go for spares, and if not then the waterpump is the issue and the rest is just icing on the cake to be complete in the swap-out of aftermarket vs OEM parts.

In any case I already know all of the stock cooling system that is left is in top notch shape.

 

[DP96XLT]

Quick follow-up...

I got all the parts in, since it is much easier to just replace the thermostat I did just that. Right away it was better in regards to temp fluctuations. It still would spike then go back down, but no-where near as much as with the MotoRad thermostat.

I am still burping the system (let it go through 2 heat-cool cycles and I can tell it is pulling more liquid from the overflow and burping a few bubbles at times, so I will let it sit overnight and it will probably be all set in regards to air pockets), and I will determine how stable temp-wise it is in a few days.

If with no air in the system it still fluctuates more than I would consider acceptable I will put in the new Motorcraft waterpump. That is the only part left that could be problematic.

Also, looks like Ford is using the same heater control vacuum valve as everyone else. So at least I have that as a spare.

With everything concerning this whole COVID-19 stuff I am more concerned that older OEM parts are going to be impossible to find. If so, I am considering ordering another thermostat and waterpump just in case there are issues in the future. Would suck to know I was stuck with aftermarket parts that ultimately could cause headaches down the line.

 

[DP96XLT]

I might also mention, a buddy that has dealt with these vehicles for a long-time stopped by. He is a ASE Master-tech and has worked at almost exclusively Ford/Lincoln dealerships.

He stopped by to give me guff about owning so many Ford products now (I was a "GM ONLY" kind of guy years ago when I was building engines/cars) and I was just running things up to temp for the 3rd time. He said he is pretty sure my engine is cammed. He figures it might be a 410, but said it has a healthier sound than he remembers that cam has, so it might be a 422 (but the custom exhaust could be amplifying it as well). He did say with the lope it has and the way it sounds when held at 2500/3000rpm that is definitely is not a stock cam. Maybe you would know, as when the engine is cold it idles perfectly smooth and even. Once it warms up and goes into open loop you get a bit of a lope to it. It is solid and consistent.

I asked him why would it be cammed with the stock air intake & stock exhaust(manifolds/muffler), and he stated that they really weren't that bad from the factory and that most people knew a simple cam upgrade made a world of difference. He asked about the rear springs and when I told him the previous owner put on the higher-rate springs he pretty much figured that proved it since rear springs and cam was what a lot of new owners asked for as the high rate rear springs kept it from squating so bad on hard acceleration.

We then went for a drive and he confirmed that it is no-where near as anemic as a stock cammed 4.0l V6 is. He said with my custom exhaust and the cold air it is WAYYY better than the stock setup. He stated if Ford sold them the way I have this one setup they would have sold a LOT more V6s since it is easily half-way or more to the V8 version. He did mention a set of headers might net me another 5-10hp, but it will push the torque band around, so if I like it now, leave it.

He couldn't confirm the shifting weirdness I have under WOT is normal or not for these. He did say that plenty of Ford auto setups in trucks have funky shifting programming from the factory. He did suggest I take it in and have a calibration check done on it, since Ford did quite a few updates over the years. It should be able to be updated, unless a newer calibration requires a different PCM altogether (he did state that has happen more than it should have over the years with a lot of Ford products) and if so it would probably be cost-prohibitive unless I go to a junkyard and find the right PCM and then have it programmed with the updated calibration, but that all counts on finding a Ford dealership that will work with me on it (he is retired now, so he doesn't have the ability to take care of me).

 

[DP96XLT]

OK, so, long story short... It is a defective radiator.

The fill neck was molded a little too tall which would not allow the stock or aftermarket radiator caps to seal at the bottom. Bent the tangs on all three caps I have now and they all work just fine.

Once the system pressurizes the variance is about 1/8 the gauge swing, which is acceptable.

I was all set to install the new Ford waterpump and it dawned on me that I might as well measure the necks on the radiators (I still have the stock one sitting in the garage). The aftermarket is 1/16-1/8" taller from the inside landing to the outside cap surface.

I am sure I could grind down the upper sealing ledge, but it has a raised bead for positive sealing and I didn't want to mess with that, so I just took the radiator caps I have and put them in a vice and bent up the catch tangs a bit higher. I did about 1/8" on all and they all seal perfectly now.

Personally I just figured that all radiator caps were like the old days where after you put them on you had a good 1/4" of pressure on the bottom "valve" to the seat. Not on newer stuff, it is all expecting a lot less tolerances.

Honestly, if I wanted to do it "right" I would take the radiator out of the vehicle and take it back... But it is in, works with this change to the radiator cap, and I have two extra caps sitting on the shelf along with a brand new Motorcraft waterpump and associated parts to redo this system at some point in the future when it needs it.

 

[96eb96]

OK, so, long story short... It is a defective radiator.

The fill neck was molded a little too tall which would not allow the stock or aftermarket radiator caps to seal at the bottom. Bent the tangs on all three caps I have now and they all work just fine.

Once the system pressurizes the variance is about 1/8 the gauge swing, which is acceptable.

I was all set to install the new Ford waterpump and it dawned on me that I might as well measure the necks on the radiators (I still have the stock one sitting in the garage). The aftermarket is 1/16-1/8" taller from the inside landing to the outside cap surface.

I am sure I could grind down the upper sealing ledge, but it has a raised bead for positive sealing and I didn't want to mess with that, so I just took the radiator caps I have and put them in a vice and bent up the catch tangs a bit higher. I did about 1/8" on all and they all seal perfectly now.

Personally I just figured that all radiator caps were like the old days where after you put them on you had a good 1/4" of pressure on the bottom "valve" to the seat. Not on newer stuff, it is all expecting a lot less tolerances.

Honestly, if I wanted to do it "right" I would take the radiator out of the vehicle and take it back... But it is in, works with this change to the radiator cap, and I have two extra caps sitting on the shelf along with a brand new Motorcraft waterpump and associated parts to redo this system at some point in the future when it needs it.

96/OHV/4sp is a very good truck for the long term. Not even broken in at your mileage. I would worry more about rust. The TSB about cooling went as far as saying to replace the 1 wire sender and even the gauge.