78 Monte 4 speed

[Geo's66]

We're on it today- he swears there's no leaks yet the dash vents don't open- hope something simple got overlooked- we'll be using the techniques mentioned above to fix the overheating- fingers crossed

 

[Texas82GP]

We're on it today- he swears there's no leaks yet the dash vents don't open- hope something simple got overlooked- we'll be using the techniques mentioned above to fix the overheating- fingers crossed

If you disconnect the vacuum line for the vents at the intake manifold and apply vacuum with the Mighty Vac, it should hold vacuum. If it doesn't, there is a leak. If it holds vacuum, try to move the HVAC doors inside the car by using the mode switch. You may have to provide additional vacuum by pumping the mighty vac.

 

[Geo's66]

If you disconnect the vacuum line for the vents at the intake manifold and apply vacuum with the Mighty Vac, it should hold vacuum. If it doesn't, there is a leak. If it holds vacuum, try to move the HVAC doors inside the car by using the mode switch. You may have to provide additional vacuum by pumping the mighty vac.

Mighty vac I assume is a tool for this? Parts store purchase item? Also, when you say use the "mode switch" can you explain? Sorry for my ignorance but thank you for the help!-

 

[Geo's66]

Answered my own question on the MV- store item @ HF, thanks.. Just need help with the mode switch you referred to- thanks

 

[TURNA]

 

[Texas82GP]

You can probably get the Mighty Vac on the loan-a-tool at your local parts store.

When I say mode switch I mean the switch in the car labeled 'heat', 'defrost', 'Max', etc. That is the switch that controls the HVAC doors under the dash. It is a vacuum switch.

 

[Texas82GP]

When a picture is worth several sentences. Well done.

 

[Geo's66]

I thought my unit was alright- I'll check that...

Is this unit pictured a new one for the MC models? Looks like it and I didn't know they were available if so? Where? Dammit, would've bought it- looks great thanks

 

[Geo's66]

Just checked - mikes montes, 81 and up models- ugh

 

[Geo's66]

Ok, pulled the heater/ac mode plate forward, used a mityvac and located the leak- there's a circular plastic switch that must've cracked over the years, that's where we located the leak. Very interesting as I pulled this apart and there's like a maze that must rotate to get the vacuum air to push/pull the flaps. Had to order the part, back on this Tuesday- should've tested this before it was re installed- ugh