So I've got a BACV (N332 off an 87 T2) that has almost no material to stick a coolant hose on the end of thanks to some serious corrosion. I decided to pull off the screws that hold the hose fittings in place and was surprised to find that the water passage was completely separate from the rest of the BACV.

What's purpose does the coolant piped to the BACV serve? Is it sensor related? Modulates temperature in the valve? Doesn't actually have any purpose and is just there because the BACV was a convenient mounting point for a hose fitting?

I need to find a way to replace this piece. I'd rather not replace the whole BACV (Mazda doesn't keep them in stock and it's not likely that anyone would sell the piece separate from the BACV used). If this hose fitting serves no purpose to the actual valve, would it be reasonable to just install a regular hose fitting that's suspended from the BACV?

I'll include pictures of the damage and the piece that I'm talking about.

 

Reuploading first picture because the editting screwed up...

 

i think its to keep it from freezing and getting stuck. little hot water goes a long ways

 

Well, I live in Arizona, which almost never experiences freezing temperatures. Do you mean actual freezing temperatures or just to warm it up if the valve gets stuck?

Also, I doodled out a crappy repair solution just uses a piece of pipe, some mounting clamps, hose clamps, and electrical tape. Thoughts?

 

The MAZDA RX-7 86-88 technical page

 

This page is awesome. You are awesome. But it mentions nothing about the purpose of coolant in the BACV.

 

Since there's no provision for regulating when the water flows (after all, it's not freezing all the time), I'd guess the main reason is to keep the BAC at a steady state temp...maybe to regulate it's consistency.

Seems like a lot of folks have deleted that water passage and suffered no ill effects.
It's a pretty crap heat transfer interface, can't be terribly effective.

 

i think it also makes the water hoses run more neatly

 

I thought the BAC was kinda like a secondary thermowax, it helps control idle depending on coolant temp

Least thats how i gathered thats its purpose

 

The ECU triggers when and how much the BAC is used. It doesn't have the ability to sense temperature directly in any fashion as the ECU wiring, and there's only one wire involved, is an output wire from the ECU and not the reverse.

 

So to sum...

Purpose: (presumed)
-Heat regulation mechanism for the BACV
-Tidies hose arrangement in the engine bay
-Does NOT actively affect the idle control or send information to the ECU

Actual effects:
-Pretty much none other than making parts corrode faster

Conclusion:
-I can get away with using a piece of metal pipe in place of the removable bit with minimal effect to the engine's operation

 

that is correct, except the "actively control idle" bit, the ECU actively controls the idle, and it does do using the BAC valve.

 

I bet the coolant is only for fast warm up emissions. Even my '98 honda runs coolant to the TB and why? I just think they want everything warm and fast.

 

Here's why:

 

Mazda couldn't have been too serious about the icing issue because that is a pisspoor thermal interface.

 

It really doesn't need much. It's a common thing on a lot of engines. The condensation from the air can condense and begin to build up ice on the valve/passages in cold temperatures. All it takes is a little heat to discourage the condensate.

 

Just get rid of it and block it off. Dont need it.

 

That's just general bad advice. The BAC is perhaps the most useful device on the car. There's almost no legitimate reason as to why you would not want it -- it keeps your car idling well, it helps prevent stalling on decel, helps with hot starts, A/C, etc.

 

I think he meant the water passage, not the BAC itself.

 

Oh, haha. Yea, in that case...