I replaced the leaky heater core in my F-350 today. Man was it a mess… rusty, sticky, gooey from some kind of sealer… just terrible.

The job went fairly well… I used the foam weather strip that came with it to replace the combination RTV and foam cover gasket that was in there… I think the core had been changed sometime in the past.

I got stung by a big black bumble bee…

Meanwhile, I had forgotten that I only have defrost… the heater selector lever isn't doing much. I had my tenant, a good friend of 20 years, start the engine so I could have vacuum to try to see what was and wasn't working on the heater. For some unknown reason, he got behind the wheel, pumped the gas pedal about six times, and flooded the engine. WTF? Must have thought the truck was a '47 not an '87. When it did start one half hour later it was getting dark and past my curfew.

So how about it heater experts… what's my next move to get some heat aimed at the floor?

BTW… I'm so darn pleased about how this 460 runs since I cleaned the throttle body last month. Smooth like buttah…...

 

Its definitely a vacuum problem. The switches don't usually go bad, and when a vac line is bad it usually throws air at the defrost and then a little everywhere else. Theres a vacuum servo under the dash somewhere, cant say exactly on your truck but on mine its on the passenger side. Check the hose to that. Other than that there should be other hoses up near the firewall. On my 300 theres a white hose that cracked on me and did the same thing. Also theres a vacuum reservoir on the blower box with a hose going to it. Maybe you knocked that off. Or maybe your truck is totally different than mine lol. Doubt it tho. Good luck and report back when u figure it out.

 

It was that way when I picked up the truck in July… just kinda forgot about it.

I'll look over the vacuum hoses… the one on the firewall next to the heater seems to be OK… I can still look under the dash.

My '97 Ram does the same as the Ford… defaults to defrost if there's vacuum problem.

Thanks.

 

Well i dont know if your ram is a turbo but usually the turbo'ed motors have a vacuume pump that can go bad and cause hard brakes and the defrost selection problem. I know my truck doesnt have a vac pump. Cant say for sure if the big block has one.

 

I'm going to venture a guess that the air flow on your '88 is the same as on my '96.

 

I would bet it is, too. Thanks for posting that… it will be a few days before I get back to that. I have a race car I have to work on first to clear off my hoist. Then the wife's Jeep gets on it so I can pull the engine apart to replace, what I think is, a broken piston.

The F-350 will get some love after that.

 

Here's a pic of that one hose going into the heat/ac box. I don't know if it will help but I had it on file and it sounded kinda relevant.

 

I'm not sure if you got this fixed already, but on my non-AC '88 truck the control for selecting where the air exists in the truck is cable-operated. If you pull out the HVAC panel you can see all the connections behind it. On mine the clip that holds the cable sheath has broken, so moving the lever moves the entire cable and sheath (thereby doing nothing). The cable loops around behind the glove box and attaches to a white plastic piece under the passenger side dash, which controls where air comes out. On mine I can reach up under the dash to move that white plastic piece and change where air exits.

Just adding this in case yours is the same way (and in case someone sees this and knows where to buy that clip!).

 

Thanks… I haven't had a chance to look at this yet.