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Outline for changing Coolant Tank Hose KM-4720, and KM-4556 - 2001 and newer 2.3 Dura


greg2u4

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Vehicle Year
2003
Make / Model
Mazda
Engine Size
2.3
Transmission
Manual
Outline for changing Coolant Tank Hose KM-4720, and KM-4556, 2001-2003 Duratec 2.3

Poster: Greg2u4 (owner of 2003 Mazda B2300 with 2.3L, 4 cyl. Duratec)

Difficulty: 7 (out of 10) - less if your a good, experienced mechanic

Time to install: 5-6 hours (if you're lucky and first learn from my and others mistakes;-)

Disclaimer: The Ranger Station.com, The Ranger Station.com Staff, nor the original poster are responsible for you doing this modification to your vehicle. By doing this modification and following this how-to you, the installer, take full responsibility if anything is damaged or messed up. If you have questions, feel free to PM the original poster or ask in the appropriate section of The Ranger Station.com forums.

Preface/Explanation:

Hello all 2001-2003 2.3 Duratec 4 cyl. Ranger and B2300 owners:

Below I’m sharing some hard-won experience I gained replacing aged and leaking coolant hoses with connections or joints in the hard to reach area behind the motor and above the bell housing and transmission. I hope this will be helpful to a few of you with these Ranger/Mazda models that have or are at risk of having this hose failure. The 2004 and newer models apparently don't use the KM-4556 hose, and I don't know what those use instead. The leak behind the motor in my case happened several years after the almost inevitable plastic tee failure on the intake manifold side. Like many of you, I improvised a replacement metal tee connector from plumbing parts after the original plastic one split. That was a much easier fix than replacing the entire hose assembly described below.

There are several related threads on different forums linked below for reference:

https://www.ranger-forums.com/dohc-2-3l-duratec-mazda-l-engines-136/2001-2-3-coolant-hose-134714/

http://www.therangerstation.com/forums/showthread.php?t=177604&highlight=coolant+leak+2.3+duratec

http://www.therangerstation.com/foru...d.php?t=167572


For my truck (2003 B2300 with 5 spd. manual) I read and found several references to the coolant tank recovery hose (Motorcraft KM-4720 - pictured within the above links and below) often being a leak culprit. I didn’t initially see info. about other hoses in back of the motor and incorrectly made the assumption it was the KM-4720 that was leaking.

The biggest lesson I learned from the whole ordeal is that the other hard-to-get-to hose that’s under and behind the KM-4720 is the Motorcraft KM-4556 and it should always be replaced together the KM-4720! They appear to be equally susceptible to failure when old. The KM-4556 is about 16 inches long with bent ends, about one inch in diameter, and connects on a metal L branch nipple coming off the hardpipe water rail that terminates behind the motor, right under the KM-4720. On the front end, it connects to a metal nipple just behind and above the thermostat housing. I ended up having to mostly repeat a lot of the steps in order to change the KM-4556 that I initially overlooked and which was the actual leaker.

After seeing posts from JMarlowe and Soledad about the coolant recovery hose job being doable without removing the tranny, the intake or exhaust manifold, or the ac compressor, I decided to give it a try. My mechanical skills are moderate, and I’ll say, having finished the job, that moderate or better skills will probably be required, along with a lot of patience and tolerance for working in extremely tight spaces. And BTW, if you’re a “big boy” with thick arms and hands, I suggest not even trying this particular approach;-)

And regardless of your physical size, those of you with above average mechanical skill, tools and equipment may find it easier to: 1) drop the tranny to get access, and/or 2) get access by removing the ac compressor and intake & exhaust manifolds.

Tools needed or suggested: ratchet, breaker bar, 15, 13, and 10mm regular and long reach sockets, good work light, specialized long reach clamp pliers or similar clamp tool. An inspection camera is helpful.

Parts Needed: Coolant Recovery Tank Hose (Motorcraft KM-4720) and companion bypass hose, KM-4556. It's also suggested to replace the KH-56 hose and the heater vacuum bypass valve the KH-56 connects to.

Steps:
For those of you who are unwilling or unable to change these hoses by doing major components removal, here’s a suggested outline, similar what was provided by to JMarlowe and Soledad:

1. If you have access to an inspection camera, use it to try to conclusively spot the exact leak source behind the motor—in case it’s not either of the hoses, such as cracked head or metal flange/housing, that will require trans. or motor removal. I ended up buying a $75 inspection camera with 38” long LED lit camera probe at Harbor Freight after my initial failure to correctly identify the exact leak source. I actually spotted some cracks/fractures in the metal (head or housings) with it, but fortunately, for now, they’re not leaking. The camera allowed me to see the dripping KM-4556.

2. If either the KM-4556 or KM-4720 are the source of the leak (and one or the other mostly likely will be), get them both in advance to replace in one operation. You will likely also need or want to replace a small hose (Motorcraft KH-56-mine got ruined during disassembly) branching off the KM-4720 near the exhaust manifold. The KH-56 connects to the heater vacuum bypass valve near the heater core. I also cracked the old plastic vacuum bypass valve during hose removal and it’s probably good to replace it regardless—the Motorcraft OEM part is only about $25.

3. Once up on jack stands, remove both front wheels and unfasten and peel back the flaps near the upper control arms on both sides, as this will allow much needed access.

4. It is recommended to use (buy, borrow, or rent) a specialty long-reach clamp removal/installation tool. In my case, I bought a $40.00 “OEM Tools” brand cable operated hose clamp pliers at Autozone. You may get by without one if you can successfully use spring hose clamps that will stay “locked open” before reinstallation. On the new KM-4720 I bought, it came with glued on spring clamps in the open position on the three hose ends. This allowed easier installation, but it was a challenge to use a screwdriver to snap closed the clamp on the small hose branch end that connects behind the motor and above the tranny.

5. Like JMarlowe, I removed the middle exhaust section which connects with two 15mm nuts to the exhaust manifold, and two 15mm spring bolts to the back exhaust section (The two oxygen or CO sensors will also need to be removed unless you can separate them from their electrical connectors).

6. I unfastened the upper and middle bolts holding the dipstick tube, which is essential for access, but I wasn’t able to pull it out of the block, so I just worked around it.

7. Remove the two 15mm nuts on the exhaust manifold studs that are holding the metal pipe section of the KM-4720.

8. Using a reliable jack under the tranny , remove the three 13mm bolts on each side of the tranny crossmember to enable lowering the tranny and crossmember by about 4 inches. At about 4 inches, the engine rests against the firewall and won’t drop any more. You will probably need this clearance for any hope of removing and reattaching hose clamps on the two hose connections at the back of the motor (one for each of the hose units).

9. After all hose connections are unfastened, you can eventually wiggle the KM-4720 out and through an approximate 1 in. space between the bottom of the exhaust manifold and engine block. In my case, I removed the old and also inserted the new KM-4720 from the exhaust manifold side of the undercarriage. I had to sharply bend the rubber part of the hose and tee that goes to the driver side connections, to get it to squeeze over the top of the tranny when reinstalling.


10. The KM-4556 is mostly positioned on the intake manifold side and should also be removed and installed from that side. NOTE: It will be easier if you install the new KM-4556 once the old KM-4720 is removed and out of the way before the new replacement KM-4720 is installed. And if for some reason you decide to position the KM-4720 in first, definitely don’t bolt it back on the exhaust manifold before the new KM-4556 is attached and clamped in back—to give yourself needed working room.

11. The only way I was able to detach the old and attach new the small hose segment of the KM-4720 on the back metal nipple was to lay down with my head pointed towards the front of the truck and reach around the tranny “barrel hug” style and do most of the work by feel rather than sight. You will likely get a fair amount of fiberglass into your arms from the disintegrating old insulation material on the firewall.

12. With the KM-4556 you can get a partial visual of the back connection point by shining a light into the opening on the driver side wheel well opening. But for that one too I had to get under and wrap both my hands around the tranny to force the new hose on, even with the expanded clamp and tool attached. The tool did not compress the spring clamp into a fully open position, and was also fussy about releasing the clamp to allow it to close and allow remove the tool.

The work took me 12 plus hours working in my spare time and I doubt I would ever want to tackle the job again, even knowing I could probably do it in half the time with the experience gained.

I’m hoping the mistakes I made and learned from will be of help to those of you who decide to tackle this challenging job. :headbang:

Greg2u4
 

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Last edited:


Rock Auto 5% Discount Code: 7FA902352B4C01: April 5th, 2021

greg2u4

New Member
Joined
Jul 25, 2018
Messages
8
Reaction score
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Vehicle Year
2003
Make / Model
Mazda
Engine Size
2.3
Transmission
Manual

Link7802

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Location
Kentucky
Vehicle Year
2003
Make / Model
Ford Ranger
Transmission
Manual
Outline for changing Coolant Tank Hose KM-4720, and KM-4556, 2001-2003 Duratec 2.3

Poster:
Greg2u4 (owner of 2003 Mazda B2300 with 2.3L, 4 cyl. Duratec)

Difficulty: 7 (out of 10) - less if your a good, experienced mechanic

Time to install: 5-6 hours (if you're lucky and first learn from my and others mistakes;-)

Disclaimer: The Ranger Station.com, The Ranger Station.com Staff, nor the original poster are responsible for you doing this modification to your vehicle. By doing this modification and following this how-to you, the installer, take full responsibility if anything is damaged or messed up. If you have questions, feel free to PM the original poster or ask in the appropriate section of The Ranger Station.com forums.

Preface/Explanation:

Hello all 2001-2003 2.3 Duratec 4 cyl. Ranger and B2300 owners:

Below I’m sharing some hard-won experience I gained replacing aged and leaking coolant hoses with connections or joints in the hard to reach area behind the motor and above the bell housing and transmission. I hope this will be helpful to a few of you with these Ranger/Mazda models that have or are at risk of having this hose failure. The 2004 and newer models apparently don't use the KM-4556 hose, and I don't know what those use instead. The leak behind the motor in my case happened several years after the almost inevitable plastic tee failure on the intake manifold side. Like many of you, I improvised a replacement metal tee connector from plumbing parts after the original plastic one split. That was a much easier fix than replacing the entire hose assembly described below.

There are several related threads on different forums linked below for reference:

https://www.ranger-forums.com/dohc-2-3l-duratec-mazda-l-engines-136/2001-2-3-coolant-hose-134714/

http://www.therangerstation.com/forums/showthread.php?t=177604&highlight=coolant+leak+2.3+duratec
http://www.therangerstation.com/foru...d.php?t=167572

For my truck (2003 B2300 with 5 spd. manual) I read and found several references to the coolant tank recovery hose (Motorcraft KM-4720 - pictured within the above links and below) often being a leak culprit. I didn’t initially see info. about other hoses in back of the motor and incorrectly made the assumption it was the KM-4720 that was leaking.

The biggest lesson I learned from the whole ordeal is that the other hard-to-get-to hose that’s under and behind the KM-4720 is the Motorcraft KM-4556 and it should always be replaced together the KM-4720! They appear to be equally susceptible to failure when old. The KM-4556 is about 16 inches long with bent ends, about one inch in diameter, and connects on a metal L branch nipple coming off the hardpipe water rail that terminates behind the motor, right under the KM-4720. On the front end, it connects to a metal nipple just behind and above the thermostat housing. I ended up having to mostly repeat a lot of the steps in order to change the KM-4556 that I initially overlooked and which was the actual leaker.

After seeing posts from JMarlowe and Soledad about the coolant recovery hose job being doable without removing the tranny, the intake or exhaust manifold, or the ac compressor, I decided to give it a try. My mechanical skills are moderate, and I’ll say, having finished the job, that moderate or better skills will probably be required, along with a lot of patience and tolerance for working in extremely tight spaces. And BTW, if you’re a “big boy” with thick arms and hands, I suggest not even trying this particular approach;-)

And regardless of your physical size, those of you with above average mechanical skill, tools and equipment may find it easier to: 1) drop the tranny to get access, and/or 2) get access by removing the ac compressor and intake & exhaust manifolds.

Tools needed or suggested: ratchet, breaker bar, 15, 13, and 10mm regular and long reach sockets, good work light, specialized long reach clamp pliers or similar clamp tool. An inspection camera is helpful.

Parts Needed: Coolant Recovery Tank Hose (Motorcraft KM-4720) and companion bypass hose, KM-4556. It's also suggested to replace the KH-56 hose and the heater vacuum bypass valve the KH-56 connects to.

Steps:
For those of you who are unwilling or unable to change these hoses by doing major components removal, here’s a suggested outline, similar what was provided by to JMarlowe and Soledad:

1. If you have access to an inspection camera, use it to try to conclusively spot the exact leak source behind the motor—in case it’s not either of the hoses, such as cracked head or metal flange/housing, that will require trans. or motor removal. I ended up buying a $75 inspection camera with 38” long LED lit camera probe at Harbor Freight after my initial failure to correctly identify the exact leak source. I actually spotted some cracks/fractures in the metal (head or housings) with it, but fortunately, for now, they’re not leaking. The camera allowed me to see the dripping KM-4556.

2. If either the KM-4556 or KM-4720 are the source of the leak (and one or the other mostly likely will be), get them both in advance to replace in one operation. You will likely also need or want to replace a small hose (Motorcraft KH-56-mine got ruined during disassembly) branching off the KM-4720 near the exhaust manifold. The KH-56 connects to the heater vacuum bypass valve near the heater core. I also cracked the old plastic vacuum bypass valve during hose removal and it’s probably good to replace it regardless—the Motorcraft OEM part is only about $25.

3. Once up on jack stands, remove both front wheels and unfasten and peel back the flaps near the upper control arms on both sides, as this will allow much needed access.

4. It is recommended to use (buy, borrow, or rent) a specialty long-reach clamp removal/installation tool. In my case, I bought a $40.00 “OEM Tools” brand cable operated hose clamp pliers at Autozone. You may get by without one if you can successfully use spring hose clamps that will stay “locked open” before reinstallation. On the new KM-4720 I bought, it came with glued on spring clamps in the open position on the three hose ends. This allowed easier installation, but it was a challenge to use a screwdriver to snap closed the clamp on the small hose branch end that connects behind the motor and above the tranny.

5. Like JMarlowe, I removed the middle exhaust section which connects with two 15mm nuts to the exhaust manifold, and two 15mm spring bolts to the back exhaust section (The two oxygen or CO sensors will also need to be removed unless you can separate them from their electrical connectors).

6. I unfastened the upper and middle bolts holding the dipstick tube, which is essential for access, but I wasn’t able to pull it out of the block, so I just worked around it.

7. Remove the two 15mm nuts on the exhaust manifold studs that are holding the metal pipe section of the KM-4720.

8. Using a reliable jack under the tranny , remove the three 13mm bolts on each side of the tranny crossmember to enable lowering the tranny and crossmember by about 4 inches. At about 4 inches, the engine rests against the firewall and won’t drop any more. You will probably need this clearance for any hope of removing and reattaching hose clamps on the two hose connections at the back of the motor (one for each of the hose units).

9. After all hose connections are unfastened, you can eventually wiggle the KM-4720 out and through an approximate 1 in. space between the bottom of the exhaust manifold and engine block. In my case, I removed the old and also inserted the new KM-4720 from the exhaust manifold side of the undercarriage. I had to sharply bend the rubber part of the hose and tee that goes to the driver side connections, to get it to squeeze over the top of the tranny when reinstalling.


10. The KM-4556 is mostly positioned on the intake manifold side and should also be removed and installed from that side. NOTE: It will be easier if you install the new KM-4556 once the old KM-4720 is removed and out of the way before the new replacement KM-4720 is installed. And if for some reason you decide to position the KM-4720 in first, definitely don’t bolt it back on the exhaust manifold before the new KM-4556 is attached and clamped in back—to give yourself needed working room.

11. The only way I was able to detach the old and attach new the small hose segment of the KM-4720 on the back metal nipple was to lay down with my head pointed towards the front of the truck and reach around the tranny “barrel hug” style and do most of the work by feel rather than sight. You will likely get a fair amount of fiberglass into your arms from the disintegrating old insulation material on the firewall.

12. With the KM-4556 you can get a partial visual of the back connection point by shining a light into the opening on the driver side wheel well opening. But for that one too I had to get under and wrap both my hands around the tranny to force the new hose on, even with the expanded clamp and tool attached. The tool did not compress the spring clamp into a fully open position, and was also fussy about releasing the clamp to allow it to close and allow remove the tool.

The work took me 12 plus hours working in my spare time and I doubt I would ever want to tackle the job again, even knowing I could probably do it in half the time with the experience gained.

I’m hoping the mistakes I made and learned from will be of help to those of you who decide to tackle this challenging job. :headbang:

Greg2u4
This was an absolute life saver. Had the hardest time just trying to figure out the part number or even the name of the hose I had leaking (KM4556), you have helped me tremendously
 


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