2-hose coolant resevoir (overflow) bottles

I've searched here and all over the internet but I'm having problems finding an answer.

When I bought my 94 (a couple of Months ago), the PO had recently put in a new radiator and water pump. I noticed that on the coolant resevoir bottle, one of the two hoses had been deleted. Someone had done the ol' bolt and hose clamp fix. The one remaining upper hose continued to feed into the driver's side Throttle body (TB). When asked, He said something about a newer style radiator being installed, negating the need for the second hose. Ok, cool. I bought the car.

Two weeks ago, I had done the TB delete, simply rerouting that remaining bottle hose to the passenger side of the engine.

Since I had owned my car, heat had been pretty lame. I'd get some warm air in the cabin, but only until I turned the blower on at which time it petered out. SO, I flushed the heater core and spent like 2-hours getting that resevior bottle clean inside. I even put some CLR in the core and let it set for about a half hour and reverse flushed, forward flushed several times. Good LORD, you should had seen the s@%T tht came out of there.

I thought I had nailed it, but tried heat again yesterday and once again, it quickly died out within seconds of turning on the blower. I went ahead and put a new thermostat in, hoping that the $12 spent would take care of the heat issue. Nope. Same issue. Quickly loses heat once you fire that blower up.

So tonight, I flushed the hell out of the core again. This time, allowing CLR to set in there for an hour and flushing-- TWICE. Surprisingly, I did get some more brown water out of there. So I'll find out tomorrow if I will need to give in and do a heater core replacement.

But....I'm now wondering about that second deleted resevior bottle hose now. Most of our LT1s I've seen seem to have a single upper hose bottle. My 94 is a double. Since I can't seem to find a diagram to save my life, I'd like to eliminate this delete as a possible source of my issues. What is the proper routing of the original upper 2-hose coolant resevoir bottle?

That hose has NOTHING to do with the heater. It was just a vent line from the radiator to the reservoir that was deemed useless by GM and eliminated during the early part of the 1995 model year. All aftermarket rads on the market come without that vent and the bottle must be capped off like yours.

One hose goes from the Reservoir to the Throttle Body and other goes from the Reservoir to the Radiator.



Odds are strongly against you ever getting that heater core flushed out properly so just replace it and be done with it.

94Woody wrote:

That hose has NOTHING to do with the heater. It was just a vent line from the radiator to the reservoir that was deemed useless by GM and eliminated during the early part of the 1995 model year. All aftermarket rads on the market come without that vent and the bottle must be capped off like yours.

One hose goes from the Reservoir to the Throttle Body and other goes from the Reservoir to the Radiator.



Odds are strongly against you ever getting that heater core flushed out properly so just replace it and be done with it.

Thanks for sharing the knowledge. I worked on that heater core most of the day yesterday as I was smoked a turkey. CLR'd that bady boy like 3 times, and when I ran out I used an industrial degreaser/surfactant. Last night as the wife and I went out to see a band, I tried the heater and it consistently put out heat. I'll be trying it again over the next couple of days to see if I indeed fixed it. If not, no big deal. I'll put in a new core.

The capped off hose looks pretty ghetto. If I come across a cheap bottle I'll likely swap them out.

If you are adventurous, it's worth removing the knock sensors to drain and flush the block. For anyone with a '96, try "Thoroflush." I'll be doing that soon on my 96s.