2002 Mazda MPV - rear heater pipe leaking

[Number_35]

Hello all -


Pipe To Rear Heater Rusted-out And Leaking. How To Plug Pipe? (OK To Disable Rear Heater!)

Per the title, this is Jr's 2002 Mazda MPV. The van developed a severe coolant leak this morning while our daughter-in-law was driving. (Murphy's Law - Our son was on a bus to help out at a summer camp which our grandson is attending.)

Anyway, we got the van towed over here, and I found that one of the steel pipes to the rear heater is rusted through. There was a plastic shield above the RR wheel which was probably intended to provide protection, but instead trapped mud.

I think the best way forward is to cut the line off before the rust and cap it.

Please suggest products I could use to cap the two lines (pipes) off. Both pipes are steel, and about 17 mm O.D. I don't know the I.D.

Another possibility is to clamp the short rubber hoses under the van, where the hoses provide a transition between the steel pipes.

I even wonder if I could loop a hose from the supply pipe back to the return pipe instead.

Ideally I could disconnect the pipes to the back up front, but access to the firewall is not good.

Any suggestions very appreciated!

 

[Number_35]

Looking toward the front - the coolant pipes are the two inner ones.

Looking up - rusty, but not yet leaking.

The culprit!

 

[SilentType]

Could you cut out the rusted sections and replace with rubber hose?

 

[The_Jeff]

If it turns out they're 5/8" pipes you could probably find some compression fittings and splice new metal line in.

Or you could use rubber hose to go back to the rear heat.

Or you could use rubber hose to make a U to the other pipe, and cut them both somewhere convenient.

 

[GSCJR]

use rubber hose to make a U to the other pipe, and cut them both somewhere convenient.

+1

 

[Number_35]

Good thoughts - is it likely Mazda used a standard hose size? The bend would be fairly tight, so I would need something flexible (or could a big snowshoe with a large bend radius).

 

[Number_35]

Could you cut out the rusted sections and replace with rubber hose?

It would be difficult. Better to abandon the rear heater, I think.

 

[fdcg27]

The problem that I can see with splicing in rubber hose would be in securing it.
Hose clamps are intended to hold hose sealed by a protrusion of the male spliced to, not a plain end.
This hose and any connections would be at whatever cooling system pressure is at operating temperature

 

[Number_35]

The problem that I can see with splicing in rubber hose would be in securing it.
Hose clamps are intended to hold hose sealed by a protrusion of the male spliced to, not a plain end.
This hose and any connections would be at whatever cooling system pressure is at operating temperature

Yes, agreed. If I used the existing flared ends of the good steel pipes, perhaps I can loop a hose back, bypassing the rotten stuff farther downstream.

At work we had duct plugs that would expand inside a conduit as an eyelet was turned on the outside end. I would be glad to try something like that.

 

[Nukeman7]

Here are a couple of products to consider:

Heater Bypass Loop

A/C Line Terminators (kinda expensive overkill)

 

[FatOrangeCat]

I had the exact same issue on my Grand Caravan years ago, rusted out at a heater line clamp area. The shop simply did a coolant hose bypass under the cowl area, and problem solved.

 

[The_Jeff]

Gates 18777 is a u-shaped 5/8" hose that is good for this sort of thing.

 

[GSCJR]

Can't remember which vehicle was prone to this back in the day; we bypassed quite a few at the shop once they found out the price of those assemblies plus installation.

 

[Number_35]

Here are a couple of products to consider:

Heater Bypass Loop

A/C Line Terminators (kinda expensive overkill)

I used similar on our 2007 Dodge Grand Caravan after the rear AC evaporator failed. The factory evaporator was NLA, and the shop had had bad experiences with aftermarket ones, so I bought high-end plug kits.

Still holding almost three years later!

*******

The coolant hose loop is appealing.

I found a factory diagram which shows a wee tee off one of the coolant lines. It is capped. I will call my excellent parts man at the dealer tomorrow to see if those caps are still available. (Mazda Canada has been very good about bringing in obscure parts for old vehicles for me.)

 

[Number_35]

Gates 18777 is a u-shaped 5/8" hose that is good for this sort of thing.

The steel lines have an O.D. of 17.0 mm. 5/8" is about 15.9 mm. I hope the hose would fit.

 

[michaelluscher]

There was a SSP for this back in the day

https://www.brakeandfrontend.com/tech-tip-mazda-leak-from-rear-heater-pipe/

https://lemon-manuals.la/Mazda/2002/MPV V6-3.0L DOHC/Repair and Diagnosis/Heating and Air Conditioning/Heater Hose/Technical Service Bulletins/Recalls/Campaign - Rear Heater Pipe/Hose Warranty Extension/Overview/

https://lemon-manuals.la/Mazda/2002/MPV V6-3.0L DOHC/Repair and Diagnosis/Heating and Air Conditioning/Heater Hose/Technical Service Bulletins/All Technical Service Bulletins/Cooling System - Coolant Leak From Rear Heater Pipe/Overview/

They revised the material from steel to aluminum, and if it's worth $166 + labor to you, you could reinstate it

2000-2006 Mazda MPV A/C Pipe LDY7-61-3BY | OEM Parts Online https://share.google/Q6rOsfqNhetb9Lxjj

Or just loop it under the hood with the gates # as mentioned before, probably more cost effective