Info needed on Coolant Hoses


Apr 6, 2006
What is the ID for the 1986-1987 Heater outlet pipe to water pump inlet hose and the Coolant bypass S-hose? Thanks!
Thanks - I am trying to verify the inside diameter of the hose. Its going on a non GN project so I don't have one to compare to. I will likely buy it from Highwaystar (thanks btw).
somewhere is a thread I did on this I did a few years ago...

Waterpump bypass hose or "S" hose = Gates 19598. When searched by year, make, model, engine, this hose is listed ONLY for the non-turbo 3.8 V6. Dayco does not make an alternate. tired of vendors listing this Gates hose as something that they specifically had made and sell it for $25+ when it is just a $6 hose made by Gates.

Heater hoses:

Waterpump to pipe 1 (3/4 inch hardpipe from heater core) = Gates 19603. Shape is correct, have to cut off a little from the ends.

Heater core outlet to pipe 1 = Gates 28474 OR Dayco 80411. Both are cut to fit.

Pipe 2 (5/8 inch hardpipe from manifold) to heater valve = Gates 28466 OR Dayco 80400. Both are cut to fit.

Heater valve to heater core inlet = Gates 28466 OR Dayco 80400. Both are cut to fit.
get them locally....skip the shipping charges.
Thanks guys - I just needed the ID, but the part numbers helped. Looks like the "S" hose (19598) is 5/8ths and the other almost S (19603) is 3/4. Great, Thanks!