Mitsubishi Montero & Montero Sport This sport utility vehicle offers more size than the other Mitsubishi SUVs, but manages to keep a sporty look and comfortable feel, unlike many larger SUVs.

Questions about COOLANT LEAK / BYPASS ...

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Old May 25, 2026 | 07:42 PM
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Default Questions about COOLANT LEAK / BYPASS ...

Hi!

RE: 2002 MONTERO LIMITED 3.5L

I would love some experienced advise, insight ...

SITUATION -- About 8-12 months ago, my mechanic noticed a possible minor coolant leak (maybe pinhole/rust at the joint) from my WATER COOLANT PIPE (L-Shaped, above the intake, connects the Coolant Crossover Pipe in the back/near firewall to the thermostat control). Two days ago, my Engine Light came on (not sure if it's related); then yesterday, my temp gauge shot up my engine overheated! I was a block from home, so I made it back, parked, and noticed major coolant leak.

NOW -- I've since ORDERED an OEM WATER COOLANT PIPE (w/ O-Rings), also an OEM intake gasket (since my mechanic will be removing intake anyway. Since I'm waiting for parts, I looked under the hood and noticed that the RUBBER HOSE that connects to the BACK/BOTTOM of the Coolant Bypass Pipe looks bad.

QUESTIONS --

1) What is this RUBBER HOSE that connects to the BACK/BOTTOM of the Coolant Crossover Pipe? Can't find it anywhere on schematics.
2) Will this RUBBER HOSE be hard to source for my mechanic?
3) I'm hoping the Coolant Crossover Pipe will be OK -- but if it's not -- would my mechanic need to remove entire engine to access/replace, or just the intake is enough?

I know the Water Coolant Pipe (L-Shaped) is bad, and this Rubber Hose is bad -- not sure what else -- but I'm hoping we don't have to change this Crossover Pipe, since labor cost might be $$$.

Anyway, any help would be great! I'm hoping my mechanic can easily fix w/o too much $. He's honest and good, so not afraid he'll be an ***. Thoughts? Thx!
 
Old May 26, 2026 | 09:45 AM
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The black hoses from the back of the engine are going to heater core inside of the cabin. I was able to find replacement hoses through many regular Mitsubishi parts websites in the past.
You do not need to remove the engine to replace the crossover pipe. It's accessible from above once the intake intake manifold is removed.
 
Old May 26, 2026 | 10:08 AM
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Thank you, @HunterD

Regarding the Crossover Pipe in the back, in case we replace, I’ve been reading that part # 1305A154 supersedes and replaces part # MD324745 … just needs longer bolts. BUT when I provide my VIN to sellers, they say this new part doesn’t fit my car, and only the previous part # matches. Thoughts? Obviously, I want the newer, updated part from OEM, but I don’t want figment issues.

ALSO — what is the heater hose (from Crossover Pipe into firewall) called? So I can help source it for my mechanic? Or maybe it’s something he should be able to source on the day? (I just know these cars are hard to source for in a lot of shops … )

Thanks!
 
Old May 28, 2026 | 12:47 AM
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Is your Montero a Full Size one, or a Montero Sport? The crossover pipe part numbers you listed are for Sport, not for Full size Montero. They are very different parts. Full size Monty does NOT have any hoses coming off the crossover pipe. The heater core hoses come from different part of the engine
 
Old May 29, 2026 | 09:36 AM
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It is not the Sport, but the Limited 3.5, so full size. And it has rear temp control, so I do believe that is a short heater hose that shoots through the firewall — I just hope mechanic can replace it without taking down the dashboard and without removing engine block!

Also,I’ve been using the Prestone All Vehicles coolant, I hope this isn’t the reason why the hose and/or pipe went bad!

Thoughts? Thx!
 
Old Yesterday | 04:30 PM
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UPDATE (but still need more answers / thoughts) -- for a 2002 Montero LIMITED, 3.5 L

So I ordered an OEM Water Coolant Pipe (PN 1310A525), the L-shaped pipe just below the intake, from "Mitsubishi Parts" on Amazon, the packaging looked legit;
AND I ordered an OEM Bypass Pipe (PN 1305A154), the updated, thicker (superseded) pipe that sits behind the engine by the firewall, from Luso Overland;

But my mechanic shows me that these two OEM parts don't sit and connect perfectly together -- looks like the L-shaped pipe is a little longer than my original, and the bypass pipe is thicker and than the original.

I called Mitsubishi and they said, according to my VIN, I have the correct part numbers! The parts guy couldn't say/guess why they're not fiiting, says it might be there the parts are not really OEM, but I've gotten OEM parts online before w/o issues.

My mechanic is gonna try to find a combo to works, and JB Weld one of them to try to fix my coolant leak issues, because it doesn't look like BOTH NEW parts can go in together. Just not sure which combo will be best.

Ugh. This coolant leak is grown to be a big headache that I'm not sure why it's so complicated to fix.

Please help if you're able! Thx!
 
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