Couple of question

[f18delta]

Just got this 85 GMC 3/4 ton a couple of weeks ago. Since then, I've been doing an inventory of what I need to get done to it so I can make it my go to when snow and ice hit. Short list is as follows:

Immediate needs:
Heater core swap
Figure out why blower motor was working and now doesn't
Fix drivers side window being stuck after rolling down
Change rubber on doors/windows

Other stuff is cosmetic:
Redo seat foam and covering
Replace jute and carpet/rubber mat or pull it all up and spray bed liner inside
Fix blinker cancelling mechanism
Replace steering wheel and fix horn
Drop some height

So here's the questions....Anyone got a good reference book or web site with pictures to replace the heater core?

I know there's a site that has a bunch of wiring info and diagrams, so I should be good with troubleshooting the blower motor.

Drivers side window seems to have had the screw holes oblonged. A friend of mine suggested a small strip of steel to tack on with a welder after marking holes and reusing screws if long enough. Any better ideas? Not worried about the cosmetic aspect of this because it will all be hidden by the door panels, but worried about possible warpage. I'm an official 4 bead welder....And all 4 were ugly! LOL

Think that about covers the initial problems and should get me through the winter. After that, I'll be researching the other cosmetic issues. Anyone think this would be better as a build thread? Even though there's not much building to be done....

[old Rusty C10]

for the heater core i have always used Chilton manuals and haynes manuals.. but also search you tube im sure someone has posted a video about it... youd be amazed on whats on that thing...

[f18delta]

Found a decent exploded diagram of the heater assembly on Autozone's web site. Was kinda surprised, but it may do the trick.

Reason I asked is because I've heard that some people have had issues with a Haynes manual when it came to the heater core. I'll try a Chilton if YouTube doesn't have anything. Thanks Bob!

[Ski-me]

Take your time doing the heater core and allow for several hours. You don't want to do it outside in the freezing weather....just pick a warm, calm day. I kinda used my Chilton's book but in actuality, I just started looking around and unscrewing things. Take a few pics along the way just in case you forget the re-assembly process.

The whole box needs to come out first....then you can attack the core removal process.

Probably the hardest part was actually getting the heater core out of the box. Study the box and how it goes apart. If I recall correctly, there is a door flapper that makes it challenging. I did it a few years ago so I don't remember the specifics. But it was WAY successful once done! My kids now LOVE the heater in the Blazer....and bonus, no more coolant smell inside!!

A lot of work for a $30 part though.....

For your blower, try getting a new relay (or find one in the junkyard). A lot of times all fan speeds work except for high. A new relay fixed it for me.

[f18delta]

Will do Jeff. Thanks!

Another item that occurred to me after driving home yesterday:

When I hit the brakes, the first half of travel makes a nice whoosh sound before I get any pedal resistance and the brakes start grabbing. Any ideas on what might cause this? I've tried the old school method of brake adjusting, putting it in reverse and slamming the brakes on, but it didn't do much of anything. I'd like to know where to spend half a day, bleeding the brakes or chasing a vaccum leak at the power booster.

[Ski-me]

Originally Posted by f18delta

Will do Jeff. Thanks!

Another item that occurred to me after driving home yesterday:

When I hit the brakes, the first half of travel makes a nice whoosh sound before I get any pedal resistance and the brakes start grabbing. Any ideas on what might cause this? I've tried the old school method of brake adjusting, putting it in reverse and slamming the brakes on, but it didn't do much of anything. I'd like to know where to spend half a day, bleeding the brakes or chasing a vaccum leak at the power booster.

Personally, I don't think the rear brakes do much anyways so the reverse thing....I wouldn't think too helpful anyways.

I'd concentrate on the front and unfortunately, that can be a can of worms!

You could try flushing out your brake fluid....I'm sure it's due. I think the fluid tends to break down over time so I would start there just as preventative maintenance.

Brake booster....don't really know but let me know how you end up testing. That's probably the only thing I have not replaced.

Then move to pads, rotors and brake lines/hoses. Of course, this leads you to new ball joints and then, while your in there, replace the front axle u-joints.

Like I said, can of worms but I've done all that! At least I know it's safe when my daughter drives it.....

[f18delta]

Well, I made it as far as ripping out the old jute and vinyl floor covering. I think I know why the previous owner said to replace the heater core. On the passenger side only, the jute had been wet at some point. After getting everything out of the floor, I cleaned up what was left and found some light surface rust where it had been wet. Got that taken care of for the most part, and moved on to removing the heater core. Figured out that I need some sort of manual before I go too much farther. I say that because I wasn't too sure about removing bolts from under the hood to get something out of the cab. Plus remembering the old 134 systems being under some decent pressure, I decided to wait.

I did figure out why the blower motor wasn't working though. The power lead for it had come off. Put that back on and it blew air through again. Looks like I'm going to have to buy a kit to replace the innards of the air box because there wasn't any air getting to the vents or the defroster. One step forward....Still wouldn't trade it though!

[Ski-me]

If I recall correctly, I think you need to remove the nuts/screws in the engine area that holds the housing to the firewall. There is one on the very bottom where I think I had to loosen the inner fenderwell to gain access to a "nut".

I also had the damp jute mat from the core too. It definitely help get that moisture out of there and also that special, sweet smell of coolant!

[f18delta]

Got it out tonight. At a price of course. I busted one of the studs that ran through the firewall. Also found that there was one of the doors that has a busted plastic mechanism on it. Guess that's why I didn't have the air rerouting when I changed from AC to vent to defrost. Other than that, I've got this weekend coming up to try and get it all back together. Still easier to work on than the Saturn I had.

[motornut]

hi hope you can glue it together
check in the airbox valve @ the pedal that valve has a (3 spots) to ajust flow
i've found them up here rigged to always have some air flow up
from floor to def...

some trucks are wired with the low fan speed always on too
I fixed mine by cutting the low speed

washers over the oblonged holes work?

[f18delta]

Originally Posted by motornut

hi hope you can glue it together
check in the airbox valve @ the pedal that valve has a (3 spots) to ajust flow
i've found them up here rigged to always have some air flow up
from floor to def...

some trucks are wired with the low fan speed always on too
I fixed mine by cutting the low speed

washers over the oblonged holes work?

In your first picture, the part that's labeled "This can break here" is the part that's broken. Not sure if I can glue it together or not, but it wouldn't hurt to try. I was nervous getting that other plastic part off, and was lucky enough to not break it when I pulled it off.

The second picture has me wondering if maybe that valve is broke. Everything was hooked up, so I'll check it out tonight and see if I can't get it working.

Thanks for the advice!

[motornut]

Originally Posted by f18delta

In your first picture, the part that's labeled "This can break here" is the part that's broken. Not sure if I can glue it together or not, but it wouldn't hurt to try. I was nervous getting that other plastic part off, and was lucky enough to not break it when I pulled it off.

The second picture has me wondering if maybe that valve is broke. Everything was hooked up, so I'll check it out tonight and see if I can't get it working.

Thanks for the advice!

oh i was suggesting the air box get"glued"
those seem to break a lot,(mine was brittle)one guy figured it out in "metal" forming it
if that is broke the other def/floor won't flow right,got to close the dash vents off

[f18delta]

Got it put back together and now need to figure out where the two hoses from the heater core hook up. Both of the hoses had been cut when the PO figured out that the core was leaking. Fixed the leak and just recirculated the coolant back to the radiator. So now I'm stuck figuring out where the hoses are supposed to be hooked into the system. Anyone got a picture or two of the hoses from the heater core to the radiator? I'm assuming that they hook into the radiator....Could be wrong. Wouldn't be the first time! I've been married for almost 20 years, so I know it won't be the last!

[motornut]

78 nonAC top pump/core/bottom intake
79 nonAC top rad/core/bottom intake
88/89 with AC top/rad/core/bottom intake

[f18delta]

I'm not following you Motornut. Let's see if I'm reading you correctly:

The top port on the heater core goes to the top radiator outlet
The bottom port goes to the bottom intake

?

Anybody got a pic of their heater core hose routing? Mine has A/C, but should route the same way as one without, right?

[motornut]

Yes I guess pics didn't load
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[Ski-me]

Top hose goes to the radiator
Bottom hose goes to the rear of the engine block

[gmachinz]

The larger 3/4 hose goes to radiator, the 5/8 hose goes to the water pump.
Posted via Mobile Device

[gmachinz]

His truck is an 85-non efi so the 5/8 hose goes to the water pump.
Posted via Mobile Device

[f18delta]

Looks like the port under the overflow was routed straight to the water pump which bypassed the heater core. Got all the hoses routed tonight and now we have heat! Problem now is that I have to drop the box again and replace both the vacuum valves on it.

Thanks for the assistance so far! I'm sure I'll be back for more!

[Ski-me]

Slow and steady, my friend! These trucks take some effort and patience but it's more satisfying when something actually ends up working after all your effort.....

[motornut]

It may depend on weither you spend more time removing heat or wanting heat
where you want the core hoses
my 78 heats faster intake/core/pump
then 79 intake/core/rad

[f18delta]

Well, in the last month or so, I've had a knee scope done and still managed to get the heater core changed out.

Got the defrost rigged to be on all the time and seems to heat the truck up quite nicely! It had the windshield defrosted before I could find the scraper and get to the windows to get them done.

I've also got the passenger side floorboard sprayed with bed liner and am liking the look / functionality of it so far.

This last weekend, I cut a 15 x 17 portion of the driver's side seat out and replaced the foam with some high density foam from Hobby Lobby. Worked great until I figured out that I was off by an inch for the height. So, grabbed another piece and glued them together. I'll put them in tonight and be driving the truck for the rest of the week since it's going to be a bit too chilly to ride the bike.

I still need some help with the window on the driver's side. I can roll it down, but it jumps out of the track at about 2/3rds of the way down. From what I can tell, the rubber has been replaced. I'm wondering if maybe the regulator needs replacing as well. Should the window stay in the wing glass track the entire way down?

[tucsonjwt]

Get a copper heater core, AC Delco if possible.

[Ski-me]

yes, it should stay in the window track all the way down. Have you taken the door panel off and checked things out? Maybe just some of the bolts are loose/missing that hold the regulator on or motor on.

Or maybe the wheel that follows the track on the bottom of the window glass is bad. About midpoint on that channel is a widening section where the track wheel can come out. Maybe something there.

To find out for sure, get the door panel off and investigate.

If you do need a new regulator, go to the junkyard. That's what I did (my wheel was broken). I think I paid $10 for it and also was able to practice taking out the glass without fear of breaking it or scratching it.

And, while you have it out...nows the time to throw a new window motor in there. I think Napa was a good place for pricing. If the motor is slow, replacing should help.