Exhaust manifolds
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Joined: Oct 2004
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From: Washington State
Repair complete
After a long pause due to being super busy, I finally had a chance to complete the work on repairing/replacing the exhaust manifolds on my '01 Montero.
When I started research on this project, my friend who is a mechanic recommended that I try to do a repair of the manifolds with welding flux sticks HTS-528. These are made by New Technology Products and designed for cast iron repair. There is not a lot of information on the interwebs for this product, but I decided that I'd try it. The decision to proceed with repair was also prompted by the fact, that a set of used manifolds I found had similar cracks (and it was also warped), so using those would not be any better than what I already have on my vehicle.
About a month ago, I had a chance to attempt to work on the repair. Unfortunately, after removing the heat shields, I discovered that driver side manifold had a much larger crack than originally thought. In fact, there were several cracks near the EGR pipe connection and they were going all the way around the manifold. This made driver side manifold not a good candidate for repair and it had to be replaced. The passenger side was confirmed to have only a single crack on the bottom side between cylinders #3 and #5. Not wanting to dish out $300+ for replacement, I still held out hope of repairing that side.
I renewed my search for new driver side manifold. I've come across $50 manifolds made in China. However, I do not have much trust in Chinese quality, so I passed on those. I finally found an international distributor who specializes in Monteros (Pajeros) and had sold only OEM parts made by Mitsubishi in Japan. I was able to get a brand new driver side manifold from them for about $140 plus shipping. I also ordered exhaust manifold gaskets (engine and pipe side) for this repair.
To start repair, I removed the air box, battery and battery platform. This opened up the space in the engine compartment and gave me better access to the manifolds. I disconnected all O2 sensors and labeled them as well as the vehicle side harness connectors in order to make re-assembly easier. I also removed both rear O2 sensors. Leaving them in place was going to interfere with removing front portion of the exhaust. In order to remove the manifolds, you have to remove the Y-pipe. Passenger side has a small section of the exhaust pipe that goes from manifold to the Y-pipe. Removing that piece first, made it easier to work with the rest of the Y-pipe and made maneuvering the Y-pipe around the front driveshaft much easier. Once I removed the Y-pipe, I was rewarded with a pleasant discovery that the driver side manifold was easily accessible from below the vehicle through the space that was previously occupied by the catalytic converter on the Y-pipe. I could easily get to three rear lower studs on the driver side manifold from there. Additionally, it turned out that this is how you have to remove both the heat shield and the driver side manifold from the vehicle. On my previous attempt, working from above, I could find any way to rotate the heat shield to get it out. Both heat shield and driver side manifold easily slid back down through the opened up space. Passenger side manifold and heat shield are easily accessible form above and can be removed through the engine compartment. Replacement driver side manifold is an OEM part and easily bolted in place. The only difficulty I've encountered with it is having to "dance" around in order to torque all the studs in sequence (from the middle out). As I said - I could get to the top three studs, plus the front lower one from top of engine compartments, while lower back three studs can only be accessed from below. That resulted in me crawling back and forth under the truck, then back to engine compartment, back under... It was annoying, but I figured that was my best chance to get good results and not damage/warp the new manifold.
Passenger side manifold was repaired using oxyacetylene welder and the HTS-528 flux sticks. In order to make this work, you have to heat the manifold to bright red color and touch the flux stick to the hot spot. The flux then melts and newly deposited material penetrates the crack and repairs it. When I first started, I was not heating manifold hot enough and was introducing the flux stick too early. This resulted in deposition of material on the surface rather than proper penetration. Additionally, when I was heating the new spot, the neighboring material would melt and be pushed away by the hot air from the welder. Once I got a hang of the procedure, I went back and repeated the process with better heating and penetration. Result as you can see is not pretty... But it worked!!! Once the manifold cooled off, I reinstalled it (with new gaskets). Installed the Y-pipe, put back two rear O2 sensors and plugged them all back together. Once all other engine compartment pieces were installed, I started the truck. It started right away and was missing only one thing - loud hissing noise from the massive exhaust leak
Everything worked. Repaired manifold is holding well and does not have a leak. The good thing is - if I do need to replace it (passenger side) some day, the process is much easier on that side. I can probably do it in 1/3 of the time it took me to do both sides.
I'm attaching some photos of the process. I hope you find this post useful.
When I started research on this project, my friend who is a mechanic recommended that I try to do a repair of the manifolds with welding flux sticks HTS-528. These are made by New Technology Products and designed for cast iron repair. There is not a lot of information on the interwebs for this product, but I decided that I'd try it. The decision to proceed with repair was also prompted by the fact, that a set of used manifolds I found had similar cracks (and it was also warped), so using those would not be any better than what I already have on my vehicle.
About a month ago, I had a chance to attempt to work on the repair. Unfortunately, after removing the heat shields, I discovered that driver side manifold had a much larger crack than originally thought. In fact, there were several cracks near the EGR pipe connection and they were going all the way around the manifold. This made driver side manifold not a good candidate for repair and it had to be replaced. The passenger side was confirmed to have only a single crack on the bottom side between cylinders #3 and #5. Not wanting to dish out $300+ for replacement, I still held out hope of repairing that side.
I renewed my search for new driver side manifold. I've come across $50 manifolds made in China. However, I do not have much trust in Chinese quality, so I passed on those. I finally found an international distributor who specializes in Monteros (Pajeros) and had sold only OEM parts made by Mitsubishi in Japan. I was able to get a brand new driver side manifold from them for about $140 plus shipping. I also ordered exhaust manifold gaskets (engine and pipe side) for this repair.
To start repair, I removed the air box, battery and battery platform. This opened up the space in the engine compartment and gave me better access to the manifolds. I disconnected all O2 sensors and labeled them as well as the vehicle side harness connectors in order to make re-assembly easier. I also removed both rear O2 sensors. Leaving them in place was going to interfere with removing front portion of the exhaust. In order to remove the manifolds, you have to remove the Y-pipe. Passenger side has a small section of the exhaust pipe that goes from manifold to the Y-pipe. Removing that piece first, made it easier to work with the rest of the Y-pipe and made maneuvering the Y-pipe around the front driveshaft much easier. Once I removed the Y-pipe, I was rewarded with a pleasant discovery that the driver side manifold was easily accessible from below the vehicle through the space that was previously occupied by the catalytic converter on the Y-pipe. I could easily get to three rear lower studs on the driver side manifold from there. Additionally, it turned out that this is how you have to remove both the heat shield and the driver side manifold from the vehicle. On my previous attempt, working from above, I could find any way to rotate the heat shield to get it out. Both heat shield and driver side manifold easily slid back down through the opened up space. Passenger side manifold and heat shield are easily accessible form above and can be removed through the engine compartment. Replacement driver side manifold is an OEM part and easily bolted in place. The only difficulty I've encountered with it is having to "dance" around in order to torque all the studs in sequence (from the middle out). As I said - I could get to the top three studs, plus the front lower one from top of engine compartments, while lower back three studs can only be accessed from below. That resulted in me crawling back and forth under the truck, then back to engine compartment, back under... It was annoying, but I figured that was my best chance to get good results and not damage/warp the new manifold.
Passenger side manifold was repaired using oxyacetylene welder and the HTS-528 flux sticks. In order to make this work, you have to heat the manifold to bright red color and touch the flux stick to the hot spot. The flux then melts and newly deposited material penetrates the crack and repairs it. When I first started, I was not heating manifold hot enough and was introducing the flux stick too early. This resulted in deposition of material on the surface rather than proper penetration. Additionally, when I was heating the new spot, the neighboring material would melt and be pushed away by the hot air from the welder. Once I got a hang of the procedure, I went back and repeated the process with better heating and penetration. Result as you can see is not pretty... But it worked!!! Once the manifold cooled off, I reinstalled it (with new gaskets). Installed the Y-pipe, put back two rear O2 sensors and plugged them all back together. Once all other engine compartment pieces were installed, I started the truck. It started right away and was missing only one thing - loud hissing noise from the massive exhaust leak
Everything worked. Repaired manifold is holding well and does not have a leak. The good thing is - if I do need to replace it (passenger side) some day, the process is much easier on that side. I can probably do it in 1/3 of the time it took me to do both sides.I'm attaching some photos of the process. I hope you find this post useful.
Senior Member
Joined: Oct 2015
Posts: 348
From: Northern VA
Good deal!
Your full size Monty has much different looking manifolds and exhaust than my Sport. Interesting that you do not have the lower torque converter bolt access location at the rear of the oil pan.
I kept my cracked passenger manifold in the event my Made In China replacement cracks. Thanks for the info regarding the brazing repair and I hope it holds. Keep us posted on its longevity. Here is a link to the HTS-528 tech sheets https://www.aluminumrepair.com/ironsteel-repair/
Your full size Monty has much different looking manifolds and exhaust than my Sport. Interesting that you do not have the lower torque converter bolt access location at the rear of the oil pan.
I kept my cracked passenger manifold in the event my Made In China replacement cracks. Thanks for the info regarding the brazing repair and I hope it holds. Keep us posted on its longevity. Here is a link to the HTS-528 tech sheets https://www.aluminumrepair.com/ironsteel-repair/
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