Heater Core

[76bonanza]

On my drive in I was greeted by a nice puddle of antifeeze on my floor on passenger side. Heater core right? How hard is it to change and does any one have a step by step instruction? Also The PO has a shut off valve on one of the heater hoses If I shut it it should stop the leak for now right? disconecting the fan would not make the heater core fail sooner would it?

[Grim Reaper]

http://www.coloradok5.com/heatercore.shtml
I say to drop the inner fender to get to that one bolt but a lot of people say with long extensions as a universal it can be done withoug removing the fender. I have air tools and it takes about 3 minutes to drop that fender on a 4x4. 2wd truck doesn't have the wheel opening clearence so you might want to try it without dropping the inner fender.


After your done let me know and I'll let you in on a little joke about that write up.

[swervin ervin]

The one bolt behind the inner fender has a stud. There is a nut on the inside over by the kickpanel. All the rest of the bolts have nuts on the outside.

[76bonanza]

I am having a hard time finding the nuts in the engine compartment I found one up top with a nut and a cable attached top right side from engine compartment. how many nut studs are there? in the engine compartment? Also was interested in checking the hoses how can you tell if they are leaking to the inside?

[Grim Reaper]

Originally Posted by 76bonanza

I am having a hard time finding the nuts in the engine compartment I found one up top with a nut and a cable attached top right side from engine compartment. how many nut studs are there? in the engine compartment? Also was interested in checking the hoses how can you tell if they are leaking to the inside?

I want to say 5. Three are at the bottom under the box and blower and two th the top where top can see them from the under hood side. The inisde one if a feel around and locate then a 8 inch extension to get it.

That inner fender out you can get to the bottm three through the fender opening pretty easy without having to hang upside down int othe engine compartment.

[76bonanza]

I might have to just pay the 90.00 bucks to have the mechanic do it I can only find 2 one on drivers side top and bottom. Can not find another one on top at all let alone any on the bottom.

[76sierraclassic]

I just recently changed mine out in my 76 GMC, and I only had 3 nuts on studs coming through the firewall. When looking from the front, one of them is on the top right of the box that has your evaporator core in it, one is on the bottom just to the left of the one on the top, and the last one is kind of on the left, and as mentioned above, it's a pain in the butt to get to. I couldn't get to it with anything I had without dropping the inner fender. Fortunately that is not a difficult task. I just removed the tire and then droped the inner fender enough to get to the bolt. Then, if memory serves correctly, there was one bolt going through from the inside. I did wonder if there were other bolts because it was fairly difficult to get the ductwork out, but it was just being stubborn. I just had to yank a little harder. I think it took me somewhere in the neighborhood of 5 hours to change out my heater core.

BTW, I don't know if you have one or not, but my Haynes Repair Manual was not a real big help on this particular project. I don't know if Chilton's would be better or not.

Hope this helps...

Mike

[76bonanza]

It should be ok with the valve closed on the supply line for a month or so right?

[76sierraclassic]

Originally Posted by 76bonanza

It should be ok with the valve closed on the supply line for a month or so right?

Yes, it should be ok. I've even seen people take the hose going into the heater core and route it directly to the inlet on the radiator to completely bypass the heater core.

Mike

[Grim Reaper]

Originally Posted by 76bonanza

It should be ok with the valve closed on the supply line for a month or so right?

Nope. System pressure will still cause it to leak unless it's totally bypassed. Just make a loop from the intake to the radiator. It will be fine till you get cold.

[76bonanza]

Grim I have a shut off inline in engine comprtment in the 5/8 supply line When I close it it stops flow thru the 5/8 line into the heater core. So even with the supply line block it will still be under pressure?

How is the easest to make loop since the hoses are different sizes?

[Grim Reaper]

Originally Posted by 76bonanza

Grim I have a shut off inline in engine comprtment in the 5/8 supply line When I close it it stops flow thru the 5/8 line into the heater core. So even with the supply line block it will still be under pressure?

How is the easest to make loop since the hoses are different sizes?

Yep. System has about 13psi on it if your cap is good. It will just back upthe return line and leak out. If that core is leaking you need to cut all coolant to it.
I would be leary about just blcoking those lines any way. I think (I would hve to look again) that the line being blocked might cause extra pressure at the Thrmostat and try to hold it closed. I think that is one of the reason GM put that bypass was to keep the pressure a little closer to even. Plus it brings the temp up a little in the radiator so that when the thermostat does open its not a slam of cold water and then the thermstat closes again. Helps even out that transision.


Just use the 3/4 line to make the loop. Radiator clamp will get it to seal on the nub on the intake.

[76bonanza]

Well stoped at napa and they had a adapter from 3/4 to 5/8 was not u shaped just striaght but will do the trick. Whopping 2.00 bucks so this week end I will loop the hoses and then in about 3 weeks will change the core.

Thanks for all your help.