Odd Cooling System Phenomenon

[ahodges]

Ok.. mine did the exact same thing last year and i can't tell you how many other people have this same problem.. there is one of 2 ways to fix it.. 1. the special water pump that ford talks about and 2. the by-pass kit..

I'll tell you right now that ford no longer makes the by-pass kit so if you go this route you have to fab one yourself..

The way i went was the water pump and it fixed the problem. I only have slight temp gauge flucuations now..

And I wouldn't be driving it more than necessary at this point, mine would rise to 220 degrees when i was having this problem.

 

[ERUSH97XLT]

I'll tell you right now that ford no longer makes the by-pass kit so if you go this route you have to fab one yourself...

What does this thing look like? What is bypassed? I can fab one up, I just need to know a little more details on this kit.

Thanks for the input. I'll try burping today. If this doesn't work, I'll build the bypass kit.

FYI: My temperature gauge never rises above the water symbol on my gauge. The highest it has ever gotten recently was in the middle of the symbol. Should I still be concerned about over heating?

ERUSH

 

[ahodges]

first off, I personally have never seen a bypass kit installed or otherwise.. You can get a diagram of it from either ford/dealer or online somewhere, Like i said i just know they're out there for the problem but I've never seen one or heard about the results

As far as the over heating.. If you are using a motorcraft temp. sending unit then the gauge is most likely reading true, but that thumping noise you hear is steam formation and you know that its hot if that is happening..

 

[96eb96]

Ok.

This sucks! It never did this before and is really annoying!

Here is what I'm going to do based on all your fine input:

I'm going to jack front end up (my driveway is flat) and burp through the service port (the highest point) behind the heater control valve. The thought behind this is to force air out of the heater core. My dad has done this technique for years with 100% success. If this fails, I'm going to pull the thermostat and do a bench test with boiling water. If it passes, then I'm going to drill a hole at the 12 o'clock position, reinstall, and re burp through the service port. This should eliminate all air pockets. Period. Then we can discuss other sources of air or assymetrical heating (combustion gas infiltration, clogs, etc.).

What do you all think? After searching the internet for hours last night, I'm pretty confident I have air trapped somewhere (thank you jremington59 for the tip!). In my opinion, this is the easiest procedure to perform (compared to removing head, etc.).

Thoughts?

ERUSH

The motorcraft stat has a tiny check ball in the hole if I recall correctly. These engines have a bleed procedure that must be performed precisely. The owners manual says it may be normal for up to 8oz of antifreeze to be added after 7000 miles! Because of the air pockets.

From the service manual:

Fill the cooling system with a 50/50 ethylene glycol and water mixture. Allow several minutes for trapped air to escape (bubble out) and for coolant mixture to flow through the radiator.

Install radiator cap to pressure relief position by installing radiator cap to fully installed position and then backing off to first stop. This will allow any air to escape, and minimize spillage.

Slide heater temperature and mode selection levers to maximum heat position.

Start engine and run at fast idle (approximately 2000 rpm) for three to four minutes. Shut engine off.

With engine off, wrap radiator cap with a thick cloth, carefully remove radiator cap and add coolant to bring coolant level up to filler neck seat.

Replace radiator cap to fully installed position. Then, back off to first stop. Operate engine at fast idle until the upper radiator hose (8260) is warm (water thermostat (8575) opens). To check radiator, shut engine off, wrap radiator cap with thick cloth and carefully remove radiator cap. Add coolant if necessary. Replace radiator cap to fully installed position.

Open the small cap on the top of the radiator coolant recovery reservoir. The large cap is for the windshield washer reservoir. NEVER put coolant mixture in windshield washer bottle.

Using a suitable suction gun, remove all coolant from radiator coolant recovery reservoir.

Add 1 liter (1.1 quarts) of 50/50 mixture of ethylene glycol and water to the radiator coolant recovery reservoir. Close the small cap.

 

[ERUSH97XLT]

I "bled" the system again through the service port today (before I read this recent post) for about a half hour. I fabricated a clear-hose connector to the service port and watched bubbles and fluid oscillation move throughout the hose. The excess that spilled out was collected in a plastic jug and returned to the service port after the engine cooled (I left the cap off for about an hour to let any bubbles escape at atmospheric pressure). I went for a test drive and there seemed to be improvement; the fluctuations were less dramatic and occured with a slower frequency. I think we've narrowed it down!

From the service manual:

96eb96,

Which service manual is this from? I have three electronic versions from FoMoCo: one specifically for the 1997 model year, another that covers 1996-1999, and a third from 2000-2004. None of these have this procedure (they have a general fill procedure), otherwise I would have followed it.

I won't have time to follow this procedure to a T tonight, but I'll get on it when I return from my road trip. I also plan on ditching the Stant T-Stat that I installed for a Motorcraft one with the bleed valve. I understand these cooling systems are quite sensitive.

Thank you kindly for the help.

ERUSH

P.S.: 96eb96, Thank you so much for the recommendation on the OBD-II scanner for my laptop! It works GREAT! I use it on all my family's cars (GM, Ford, Toyota, new and old). I have recommended this to a few of my gear-head friends, too!

 

[96eb96]

I "bled" the system again through the service port today (before I read this recent post) for about a half hour. I fabricated a clear-hose connector to the service port and watched bubbles and fluid oscillation move throughout the hose. The excess that spilled out was collected in a plastic jug and returned to the service port after the engine cooled (I left the cap off for about an hour to let any bubbles escape at atmospheric pressure). I went for a test drive and there seemed to be improvement; the fluctuations were less dramatic and occured with a slower frequency. I think we've narrowed it down!



96eb96,

Which service manual is this from? I have three electronic versions from FoMoCo: one specifically for the 1997 model year, another that covers 1996-1999, and a third from 2000-2004. None of these have this procedure (they have a general fill procedure), otherwise I would have followed it.

I won't have time to follow this procedure to a T tonight, but I'll get on it when I return from my road trip. I also plan on ditching the Stant T-Stat that I installed for a Motorcraft one with the bleed valve. I understand these cooling systems are quite sensitive.

Thank you kindly for the help.

ERUSH


P.S.: 96eb96, Thank you so much for the recommendation on the OBD-II scanner for my laptop! It works GREAT! I use it on all my family's cars (GM, Ford, Toyota, new and old). I have recommended this to a few of my gear-head friends, too!

Yup that scanner is one of my favorite toys! I can't imagine owing a car without it! Glad you enjoy it.

Also, if you go on the motorcraft site the procedure is actually listed in the OWNERS MANUAL believe it or not! They were pretty darn serious about bleeding that engine correctly.

I copied this info from the 1996-2001 DVD under ENGINE-COOLING SYSTEM DRAIN AND FILL. There are variations for 96 and 97 but the idea is the same.

Yes, they are very sensitive. I was told by someone higher up at Ford that the Motorcraft stat was revised a handful of times and is the only unit that should be used in these engines. I was told it also is designed to prevent engine failure due to overheating, it has somewhat of a failsafe design(don't know, but the guy seemed to know what he is talking about). Also, changing the one wire sender (if its original) may help a bit with the gauge readings too. That is optional though.

 

[ERUSH97XLT]

I was told by someone higher up at Ford that the Motorcraft stat was revised a handful of times and is the only unit that should be used in these engines. I was told it also is designed to prevent engine failure due to overheating, it has somewhat of a failsafe design(don't know, but the guy seemed to know what he is talking about).

I checked Motorcraft's website, and they make four different "Engine Coolant Thermostats" for the 4.0L OHV engine (so it seems), each with different part numbers: (1) 8575 (RT-1086) OHV; Thermostat-197, $31.08; (2) 8575 (RT-1105) Thermostat, $18.96; (3) 8575 (RT-1160), $55.22; and (4) 8575 (RT-1161); $31.08.

Anybody know the difference between these? My gut feeling is to go with the one with OHV; Thermostat-197 since it explicitly says for the OHV.

ERUSH

 

[96eb96]

I checked Motorcraft's website, and they make four different "Engine Coolant Thermostats" for the 4.0L OHV engine (so it seems), each with different part numbers: (1) 8575 (RT-1086) OHV; Thermostat-197, $31.08; (2) 8575 (RT-1105) Thermostat, $18.96; (3) 8575 (RT-1160), $55.22; and (4) 8575 (RT-1161); $31.08.

Anybody know the difference between these? My gut feeling is to go with the one with OHV; Thermostat-197 since it explicitly says for the OHV.

ERUSH

Rockauto lists:
MOTORCRAFT Part # RT1161 {#F2TZ8575A, YU3Z8575BA}
OHV

$18.19 $0.00 $18.19
Add to Cart

This is for any 4.0L OHV engine from 90-00. Don't forget a 5% discount code (search online) if you buy anything from them!

 

[ERUSH97XLT]

Thanks for the resource, 96eb96!

Here's another wrench in the works:

When I was burping through the service port, the gauge never oscillated or fluctuated. Period. The needle touched the water symbol, and lowered to indicate the thermostat opened. Does confirm that I have air in the system? My thought behind this is pressure. . . when the system is under pressure (e.g., when all caps are closed) the gauge oscillates. When the system is under atmospheric pressure (e.g., when the radiator cap is off or when the service port is open) it doesn't. If this is the cause for my troubles, there obviously has to be a pressure relief solution (a by-pass kit does this?). I already replaced my radiator cap, but is there another cause for this? I know I need pressure in order to prevent steam formation, but maybe there's something missing from this puzzle.

Any thoughts? Or am I being too much of an engineer. . . ?

ERUSH

 

[96eb96]

What does this thing look like? What is bypassed? I can fab one up, I just need to know a little more details on this kit.

ERUSH

http://www.explorerforum.com/forums/showpost.php?p=1653528&postcount=16

 

[GRNMACHINE]

Interested in hearing about the outcome/subscribing. I replaced my tstat last year with a Motorcraft one, purchased at a dealer and they said there was only 1 part no. for 1995 OHV.... I believe it was around $18.

Also, can you tell me more about the OBD-II scanner for laptop? Interested.

Thanks

 

[ERUSH97XLT]

Interested in hearing about the outcome/subscribing. I replaced my tstat last year with a Motorcraft one, purchased at a dealer and they said there was only 1 part no. for 1995 OHV.... I believe it was around $18.

Also, can you tell me more about the OBD-II scanner for laptop? Interested.

Thanks

http://www.explorerforum.com/forums/showthread.php?t=225969&page=3

http://obd-2.com/

This thing is sweet! Worth EVERY penny.

http://www.explorerforum.com/forums/...8&postcount=16

Great link! Let me get this straight: This bypass kit short-cuts the port for the ECT sensor to the lower radiator hose? Is this right? This sounds easy to make. I'll get on it if all else fails (motorcraft thermostat, more burping, long drives, etc.).

Thank you all for the help. I'll be away for the weekend , but I'll update as soon as I return.

Best,

ERUSH

 

[96eb96]

http://www.explorerforum.com/forums/showthread.php?t=225969&page=3

http://obd-2.com/

This thing is sweet! Worth EVERY penny.



Great link! Let me get this straight: This bypass kit short-cuts the port for the ECT sensor to the lower radiator hose? Is this right? This sounds easy to make. I'll get on it if all else fails (motorcraft thermostat, more burping, long drives, etc.).

Thank you all for the help. I'll be away for the weekend , but I'll update as soon as I return.

Best,

ERUSH

Yes, I believe it allows some coolant to bypass the the radiator and tstat. Most engines have an external bypass tube, I believe the 4.0 has it in the manifold and its very small. I guess you can get some T fittings and heater hose to fabricate this. The sender port fitting may be a bit hard to find.

Have a great trip!

 

[ERUSH97XLT]

I'm back!

I'm back from a 650 mile road trip. I didn't over heat or blow a hose, but this long trip gave me PLENTY of time to run some cabin-heater experiments and maybe churn the coolant enough to burp some air into the reservoir.

Here are my observations:

When I turn the climate control knob to "Off" or to "Max A/C", the needle quickly stabilizes to its usual operating temperature point. All other conditions yield the aformentioned fluctuation.

This clears all aspects of the cooling system (including sensors and senders) except for the heater core circuit. This fluctuation has to be part of the Heater Core/Heater Control Valve circuit. My working theory is the following:

1. Air is trapped in the heater core, causing temperature cycling due to pressure fluctuations. Remedy: Raise the front end up as high as possible (thus making the heater core the lowest point) and burp according to the Ford procedure.

Or

2. The heater control valve is slightly malfunctioning and not permitting air to pass through the valve. I have heat, so it's allowing coolant to pass. Remedy: install hose barbs and seal the vacuum source to eliminate the heater control valve; if the needle stabilizes, replace the valve.

What do you all think? Does anybody out there have experience with burping the heater core?

ERUSH

 

[Vargas]

Am I mistaken about the heater core circuit plumbing? I thought it was constant flow, with the cabin temp control moving a blend door that regulated mix of hot and cold air. If I am correct that there is no coolant control valve, then the problem is not the heater core, since nothing changes the flow configuration when the cabin controls are moved.

 

[backfrmcolorado]

that is very annoying i know. ive had the same problem now for three yrs. i even redid my whole cooling system, new water pump, all hoses, therostat, oversized rad, new cap,new heater control valve and flushed with all new 50/50 coolent and still the same problem. i do have a 94 x but in sure its all the same as yours. it goes halfway up the guage then all the way below the bar below (N) of the normal letters. it dosent overheat or anything, but when i fill up on gas or check/change oil i alway check collent and always end up haveing to put more antifreeze in and burp the system about every three months. when you get this figured outid like to also know how to fix it.

 

[ERUSH97XLT]

Am I mistaken about the heater core circuit plumbing? I thought it was constant flow, with the cabin temp control moving a blend door that regulated mix of hot and cold air.

There is a heater control valve that either allows coolant to pass through or by-pass the heater core circuit. This valve is open (allowing coolant to pass through the heater core) in most modes of climate control; however, at least in my vehicle, the valve closes when the climate control knob is in the "OFF" or "MAX A/C" positions. The theory here is when "MAX A/C" is engaged, absolutely no heat is entering the cabin. Thus the heater core must be by-passed. Same theory when the knob is in the "OFF" position.

Track your heater hoses. Near the firewall on the passenger side, you'll find a valve with a vacuum actuator. That's the Heater Control Valve.

ERUSH

 

[Vargas]

There is a heater control valve that either allows coolant to pass through or by-pass the heater core circuit. This valve is open (allowing coolant to pass through the heater core) in most modes of climate control; however, at least in my vehicle, the valve closes when the climate control knob is in the "OFF" or "MAX A/C" positions. The theory here is when "MAX A/C" is engaged, absolutely no heat is entering the cabin. Thus the heater core must be by-passed. Same theory when the knob is in the "OFF" position.

Track your heater hoses. Near the firewall on the passenger side, you'll find a valve with a vacuum actuator. That's the Heater Control Valve.

ERUSH

Oh, I see. I knew there was a blend door, and I knew that there were no cables on the control panel for actuating a valve. It did not occur to me that the valve might be vacuum operated.

 

[EastoutWest]

I know this thread is a bit old, but I wanted to throw in some of my recent experience

Mine is a 91 with no heater core bypass. I replaced my thermostat with an Advance Auto part because the engine wouldn't heat up so I figured it was stuck open. I had already replaced the temp sender because the gauge wasn't reading at all. I ended up with the same air bubble problems with the fluctuating gauge. I found that it would fluctuate the most on acceleration or deceleration.

So I bought a flush/fill kit for $4. I ran hot water into the heater hose t-fitting that came with the kit... flushed the %$&* out of it, letting water run out of the radiator cap, overflow reservoir, drain plug, at various times. I got it to burp alot. Used an entire water heater of hot water. It now has pure water (and still some rust) in it and the fluctuations have decreased considerably. It also runs a bit warmer than before the thermostat change, but it is still low. Most of the time, even in 90 degree weather in traffic, it still runs below normal...

I am reluctant to open the system back up to put a motorcraft thermostat in, but I will have to eventually because I will need to flush it again and replace the water with antifreeze mix.

Long story short, the flush/fill kit helped remove the trapped air, but it still runs too cool and fluctuates more than it seems it should. Maybe next time I'll park the truck on an incline like suggested in this thread.

 

[ahodges]

Part # for water pump

so it's been a while since I've posted to this thread but I finally figured out the part number for that water pump through Ford that fixed my problem which sounds like all of yours.. For those who haven't seen my previous post it is the first one on the second page of this thread.

I had major temperature fluctuations and tried everything to fix it including replacing the temp. sending unit, thermostat, fan chutch, and replaced the water pump with another stock one and none of it solved the problem. I finally gave up and took it to the dealer. After they played with it and researched it for 4 days they came to the conculsion that they were going to try this specialized water pump that Ford suggested in a TSB about this problem.

The Ford part number is 97TM-8505-AC.

The only down fall to this pump is the price.. it retails for around $200. I got a deal on mine for $100 and the whole ordeal at the dealer only cost me $400 because they felt bad they couldn't figure it out in a timely manner.

Best of Luck!