88 Silverado Heater gone bad.

[Donbinnc]

I have a 1988 CK 1500 Silverado. I have an antifreeze smell in the cab and the obvious wet spot on the passenger side floor board. Also the defrost mode does not completely clear the windows. I found that the radiator coolant level is low and added almost a gallon of antifreeze/coolant.

Other than the obvious indicators I mentioned before I pretty sure the heater core has gone bad. Is there any other way to see if the heater core has gone bad?

If it is bad is it difficult to replace? Can anyone provide me replacement instructions or point me to instructions on the web?

Thanks.
Don

[j cAT]

Originally Posted by Donbinnc

I have a 1988 CK 1500 Silverado. I have an antifreeze smell in the cab and the obvious wet spot on the passenger side floor board. Also the defrost mode does not completely clear the windows. I found that the radiator coolant level is low and added almost a gallon of antifreeze/coolant.

Other than the obvious indicators I mentioned before I pretty sure the heater core has gone bad. Is there any other way to see if the heater core has gone bad?

If it is bad is it difficult to replace? Can anyone provide me replacement instructions or point me to instructions on the web?

Thanks.
Don

heater core is not much of a problem with your old vehicle.

put air pressure into the heater core hoses see if it holds pressure . 15psi max. if its not corroded when you remove it possible solder repair.

they made these very strong in the old days.

use distilled water with coolant used. this reduces corrosion.

[Schurkey]

Heater core won't be any fun.

The one in mine ('88 K1500 regular cab) is aluminum; you won't fix it with solder. MAYBE some '88's got copper/brass cores, but I doubt it.

WHILE YOU'RE IN THERE, check on the foam gaskets that seal the joints of the heater box assembly. My foam was totally rotted--looked like foam until I touched it, whereupon it disintegrated into goo. My truck was always cold in the winter, warm in the summer--the gasket that seals the recirculation box to the firewall was practically gone, and created an enormous non-heated, non air-conditioned air leak.

I had to pull the whole dash down to fix the rotted gaskets. If I can find photos, I'll post 'em. I think they're on my other computer. Steering column comes OUT, entire dash tilts down about 45 degrees on a pivot. Basically lays on top of the seat. Kinda cool to see it that way...but there's still crappy access.

WHILE YOU'RE IN THERE, pull out the blower motor, and see if you can dig out all the pine needles, leaves, and other crap plugging the front of the A/C evaporator. I spent an hour or more blowing compressed air from the front, sides, and rear; dislodged a ton of crap. Between the compressed air and a shop vac, I got it pretty clean. Much better air flow through the ducts.



[Robot Voice]DANGER, WILL ROBINSON![/Robot Voice]
The 1988 GM official service manual DOES NOT provide the proper procedure for removing the far-right section of the blower/recirculation box. The box WILL NOT come out using that procedure. The correct--and much more involved 'n' difficult 'n' expensive--procedure is in the service manual SUPPLEMENT published later AFTER they figured out what they screwed up in the main service manual. I hope you don't need to remove that far-right box to replace the heater core. (I had to take it out to replace the rotted foam gasket)

[Schurkey]

Originally Posted by Schurkey

If I can find photos, I'll post 'em.

No photos of the dash removal. Some nice ones of the far-right recirc/blower box removed; but nothing that'll help you unless you have to pull that apart due to rotted gaskets.

Sorry. Didn't take enough pictures...

[j cAT]

Originally Posted by Donbinnc

I have a 1988 CK 1500 Silverado. I have an antifreeze smell in the cab and the obvious wet spot on the passenger side floor board. Also the defrost mode does not completely clear the windows. I found that the radiator coolant level is low and added almost a gallon of antifreeze/coolant.

Other than the obvious indicators I mentioned before I pretty sure the heater core has gone bad. Is there any other way to see if the heater core has gone bad?

If it is bad is it difficult to replace? Can anyone provide me replacement instructions or point me to instructions on the web?

Thanks.
Don

I did some looking on this work your doing and the interior air box needs to be removed . the top screws are hard to get at. also the passenger side screw. with the plastic box removed the core will be visible.

[bigwoody555]

My `88 K1500 is leakin at the heater core also. Is this a hard fix?

[Schurkey]

Originally Posted by bigwoody555

My `88 K1500 is leakin at the heater core also. Is this a hard fix?

It is if you're going to replace all the shitty, degraded foam seals so the HVAC actually works right again.

I had a shop replace my heater core (I thought it was plugged.) Made no difference in the interior warmth because of the enormous cold-air leak at the cowl-to-heater box seal, as detailed in my post above.

Replacing the core fixes your coolant leak. Replacing the foam (and verifying that the actuators work properly) makes the air go where it needs to.

If the core has rotted out, be sure to flush the old coolant. Would be worth your time to verify coolant voltage afterwards, too.

[bigwoody555]

Seems as if the foam is OK. How long to pull the core? Does it remove easily from behind the blower motor? Thank you for your assistance!

[Schurkey]

Originally Posted by bigwoody555

Seems as if the foam is OK. How long to pull the core? Does it remove easily from behind the blower motor? Thank you for your assistance!

Not sure, since I didn't replace mine--had it done by a shop years before fixing the foam.

The A/C evaporator is next to the blower motor. Heater core is below.

[bigwoody555]

4 screws for the heater box. 1 screw holding the core. 2 hose clamps. A 30 minute job. Piece of cake!!!

[j cAT]

Originally Posted by bigwoody555

4 screws for the heater box. 1 screw holding the core. 2 hose clamps. A 30 minute job. Piece of cake!!!

thats what I found which is what I said in the earlier post. just that the screws may be hard to get at ,but not a big job on the older 80's vehicles .

with the 2000 silverado I have it is a big job.