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Zuke, definitely back-flush the heater core. And consider changing the molded hoses to the straight bulk hoses as Best has suggested.
I had a similar problem with a semi blocked heater core. As the truck would come to temp the hose (like in your pic) would collapse on itself at the bend. It was slight, but with an already compromised flow in the core =
I back-flushed the heater core a few times, replaced the molded hoses, burped the beast and it was back to Happy Town!
I grabbed a 6ft piece of 5/8 heater hose at Oreilly's for like 8.00. I also highly recommend carefully cutting the old heater hose off especially on the heater core side. You don't want to stress out the lines to the core at all. I then loosened the bolt that holds the two metal heater lines together on the engine, swung it out of the way a bit, and installed the inner 5/8 line and new SS clamp, then I re-installed the bolt for the heater pip brace, and did the outer one. After that I was in business!
I also highly recommend carefully cutting the old heater hose off especially on the heater core side. You don't want to stress out the lines to the core at all.
100% so true!
I remove the clamp and with light pressure make a single slice through the hose with a razor knife.
The key as you mentioned is "CAREFULLY"!
It takes very little effort to cut the hose, but too much and you can go through the aluminum heater core feed lines.
I would have never thought that could happen until I saw someone do it....what a mess.
As for the bulk 5/8" replacement hose I like to use Silicone (Vibrant Performance because I got it cheap).
It lasts long and it's very flexible while maintaining the proper shape you put it in.
Overkill, probably...and rubber hose is fine as long as it's rated FOR COOLANT and NOT fuel.
I can't tell you how many times I've seen people have the hoses to the throttle body heater plate leak because they use a fuel hose.
And just for Giggles, here is the coolant flow according to RAVE.....OMG way too much free time today!
Last edited by OverRover; Aug 8, 2018 at 06:48 PM.
The routing of the heater core lines is totally irrelevant in/out of the heater core. It’s a closed loop nothing more. As a matter of fact look up any older RRC or 94-95 D1 with the 3.9L V8 and they are routed straight in/out vs crossed.
All it really does on a D2 = required you to buy the fancy one piece OEM hose vs some 5/8 heater hose cut to fit.
Also the Rave flow directions are correct. When my core finally clogged hose #4/#3 was hot while hose #9/#2 was cold. So I knew I had flow to the core & nothing coming out. Back flushed it & then routed my new hoses in/out straight vs crossed and it works flawless.
