mystery coolant hose - unable to identify

I have a 1996 C1500 4.3 and the water pump has two small hoses coming out of it. I was able to determine one of them is a bypass hose. 2 hours of research, i can't identify the other hose of roughly same size and ID.

anyone know what this hose is called, or a part number? im trying to replace entire cooling system but i have this hose with no name. i cheaked all the websites. for 2 hours. hoses are 27 years old and about to burst.

really need to order this tonight

theres no name or numbers for this hose. there is no info on google, rockauto, advance, oreillys, napa, carquest, nothing. no cooling system schgematic to identify the hose. i could probably get a generic one and flex it but figured there would be a replacement part out there somewhere, thought these engines have been around awhile?

Heater return hose

The hose you identified yourself as a “bypass hose” is marked 322 in the following diagram:



That hose is the engine coolant bypass hose. You’re not finding the other hose in the same diagram because it serves a different function (heating rather than cooling).

The hose you are searching for is the heater outlet hose assembly. It is marked 4 (although 7 is the hose that connects directly to the water pump) in the following diagram:



4 is GM P/N 15708635. The diagram appears to show other hoses that follow the same route (e.g., 7 and 10 in the diagram), but per another website, GM P/N 15708635 actually includes 6, 7, and 10 in addition to 4. So, that is basically the entire heater outlet hose assembly.

If you browse the internet for a photo of 15708635, you can confirm its appearance. For example, this photo from Amazon:



Long story short, you need GM P/N 15708635, heater outlet hose.

xXxPARAGONxXx said:

The hose you identified yourself as a “bypass hose” is marked 322 in the following diagram:

You must be registered for see images attach

That hose is the engine coolant bypass hose. You’re not finding the other hose in the same diagram because it serves a different function (heating rather than cooling).

The hose you are searching for is the heater outlet hose assembly. It is marked 4 (although 7 is the hose that connects directly to the water pump) in the following diagram:

You must be registered for see images attach

4 is GM P/N 15708635. The diagram appears to show other hoses that follow the same route (e.g., 7 and 10 in the diagram), but per another website, GM P/N 15708635 actually includes 6, 7, and 10 in addition to 4. So, that is basically the entire heater outlet hose assembly.

If you browse the internet for a photo of 15708635, you can confirm its appearance. For example, this photo from Amazon:

You must be registered for see images attach

Long story short, you need GM P/N 15708635, heater outlet hose.

Click to expand...

thank you for the info and the links! i have C60 manual controls so im not sure if that's the right part for me or not, the parts im always interested in are never listed below the diagram. i would want #10 and #4 in this diagram, and there may be others i have missed. should i be replacing any other hoses when replacing pump, water pump bolt kit, thermostat, thermostat o-ring, thermostat housing, radiator, fluid resevoir, upper and lower hoses?

Also, should i be doing anything more than using a garden hose to hose out the block where the thermostat is?

As far as #7 and #322 i beleive them to be the same hoses in an ACDELCO 14155S and i trim the shorter one to fit. Could be wrong but thats the best i could come up with so i ordered 2.

I admire the research you and others have put into this (xXxPARAGONxXx, very nice response from you).

Here's what I think would do the trick, from RockAuto etc.:

ACDELCO 10242185 (Item 7) water pump inlet hose
- see RockAuto CHEVROLET > 1996 > C1500 PICKUP > 4.3L V6 > Cooling System > Coolant Hose / Pipe

ACDELCO 14155S (Item 322) bypass hose
- see RockAuto CHEVROLET > 1996 > C1500 PICKUP > 4.3L V6 > Cooling System > Bypass Hose

Item #10 is just "bulk heater hose" you can buy at NAPA / et al. and have cut to length. I think this hose is 5/8" but *check*.

Regarding Item #1, I suggest you eliminate the quick-connect fitting in the manifold and replace it with a restrictive nipple, such as GM 1533220 (about $9 at RockAuto, see thread https://www.gmt400.com/threads/rest...eater-qd-udated-delco-fitting-15-33220.56182/)...

... and then use either bulk heater hose (3/4") or a ""gooseneck" molded 3/4" hose as a replacement (Gates 28480, 52" long or 28481, 64" long, get one that's "too long" and then cut to length; RockAuto has Gates' 28481, about $14).

Item #4 is an OEM piece of bent pipe that you can almost certainly reuse, as I have.

The upper and lower radiator hoses should be available from RockAuto.

If the constant tension (OEM) hose clamps are still on the hoses, reuse them when you put the new ones on. Those clamps work very well for their intended function.

The Gates Molded Hose ID Guide is invaluable to any project. It provides part numbers, sizes, descriptions and pictures for all their hoses. Find it here, at Gates' site and others.

Stringer, that drawing in your last post is pretty funky, it shows a engine / hose configuration for a 4.3L Suburban with rear heat(!).

Was the 4.3L *ever* put in a Suburban???

not sure, i put in my truck info and thats what the site showed me lol. thanks for all this great info!!

i test drove the truck for 10-15 minutes and according to the gauge it barely got warm. the thermostat that came out is a "WAXSTAT 92", is that the wrong one i wonder?

No, it is the correct temperature. 92C is 198F, which is OE spec.

The factory gauges tend to be wildly inaccurate, so don't trust that. Get an infrared thermometer and check the temperature of the thermostat housing once the engine is at operating temperature, or get a scanner that reads live data and see what the ECM is seeing for coolant temp. My truck runs just above 1/4 way mark when the engine is at 195 degrees.