9C1 silicone hose heater core bypass

A co-worker of mine generously gave me the silicone hoses off a 9C1 police Caprice he parted out. On the lines to/from the heater core, there's a couple of tees and a bypass hose between them. Anyone know why this would have been done? I have another set of heater hoses off another 9C1 equipped Caprice and they aren't hacked in this way.

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Someone will chime in with the answer, but I wanted to point out you should look into the correct clamps for these hoses. They are silicone and used a different type of clamp that did not risk cutting into the material when tightening.

Yep, I am aware of that. I have the proper stainless steel clamps for silicone hoses on-hand. The fact that it has those clamps on it certainly leads me to believe it to be non-factory.

Might have had a coolant filter at one time. I have tees in my heater hoses for exactly that.

maybe a home brew technique for flushing the system????

I'm going to guess that this was done to reduce the amount of heat getting into the cabin. Police cars do tend to sit idling for hours at a time.

They may have come from a 91 that had a vacuum operated bypass valve to stop water flow to the heater core when the AC is on.


You are also missing the restrictor for the non bypass systems. The "rigged" set of hoses may be compensating for that omission.

The restrictor is there, just not on that side of the hose set. Thankfully I ended up with two sets of 9C1 silicone heater hoses, because one of the restrictors had gone out-of-round and wouldn't seal properly! Since those were already cut I had some ability to do some physical "cut and paste".

Oh that reminds me, I used a brass connector to splice the hose together, and I'm curious if that's a known bad idea. Galvanic corrosion or other issues, perhaps?

There is a sacrificial anode in the system to keep the galvanic activity in check. Plastic is preferred, because it is for the most part inert.

Fred, if there is (was) a sacrificial anode in that system somewhere, I'm sure it was sacrificed.

The inside of that block is coated in rust!

So, think it through. If the sacrificial anode is gone, how does adding another dissimilar metal added to the mix affect the system.

I'd say it depends, Fred. There's already dissimilar metals in the system, so really only 3 things can happen here. 1: the corrosion inhibitors will prevent anything bad from happening (until they wear out), 2: the addition of brass will accelerate corrosion, or 3: the brass itself becomes sacrificial and slowly dissolves over time until the thing starts leaking

I'm waiting on some more ABA hose clamps, so next opportunity I get after that I'll install a (plastic) flush tee where that brass coupler is now, just in case. I'm also thinking about adding a screen to catch the little bits of engine block rust that are floating around there.

Run a coolant that contains molybdate. That will protect any brass in your system. Dissimilar metals cause so many problems in cooling systems, because most coolants are equipped only to protect a narrow range of metals. Different inhibitors protect different metals. Certain inhibitors that protect one metal may also set about destroying another metal.

That's why I run Rotella Ultra. It loves all metals and solders.It's like a big, fat, kind, happy foster mother for your cooling system.

Good tip! thanks

lamune wrote:

or 3: the brass itself becomes sacrificial and slowly dissolves over time until the thing starts leaking

The most active metal (ie: able to liberate hydrogen from the electrolyte) will be the sacrificial anode. At the really active end of the scale are metals like Magnesium, Aluminium, Zinc and Iron.

Towards the middle are metals like Nickel, Tin and Lead, which require a fairly acidic electrolyte.

At the non-active end of the scale are Copper, Silver, Platinum, and Gold.

Brasses are alloys of at least two pure metals, and the activity level varies a bit by the specific alloy. However, most brasses are generally even less active than most stainless steels. So your brass won't be the sacrificial metal.

The flip side is that the greater the difference between two metals, the faster the more active one will corrode. So the presence of brass will accelerate the corrosion of the aluminium, since it is probably less active than the iron.

I wanted to follow up on this with some garage science based on what buickwagon posted and what I remember from chemistry class.

I did replace the brass connector with a plastic one (Prestone flush tee, which may come in handy) once I got hold of some nice marine grade hose clamps.

I put the brass connector and a piece of the aluminum tubing from my old heater core and put them into a small cup, I added some filtered water and attached them to a DVM. I read 590mV, with the brass being the positive terminal, meaning that the aluminum is the anode in this chemical battery. That seemed a lot higher than I expected. Then I replaced the water with some 50/50 mix of Prestone and distilled water. Even more surprisingly, I get 632mV out of that battery, again with an aluminum anode. I didn't have a piece of cast iron on hand to test that, but based on this, it seems like there would be a galvanic reaction in antrifreeze between a brass fitting and the aluminum in the cooling system.

So, it's probably best to stay away from any metal aside from aluminum and iron which are already in the system, or go with gold or platinum if you can afford it.

If there's really a sacrificial anode in the system, does anyone know where it would be? I did some digging and can't seem to find any mention of it. There aren't too many places you could stick it.

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lamune wrote:

Then I replaced the water with some 50/50 mix of Prestone and distilled water. Even more surprisingly, I get 632mV out of that battery, again with an aluminum anode.

Wow. I sure didn't see that one coming. Who'd have thought that Prestone is a more efficient electrolyte than water? No wonder things corrode in there. Neat experiment.