The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 10-17-2015, 01:27 AM   #1
E.D.75GMC
Registered User
 
E.D.75GMC's Avatar
 
Join Date: Aug 2013
Location: Calgary Alberta
Posts: 273
Thermostatic air cleaner isn't working

So the flap in the air cleaner that diverts hot air from the exhaust manifold into the carburetor has stopped closing, and as such it's pulling in cold outside air on a cold start. Just in time for winter of course. I checked the vacuum line to the carb it's okay, so I'm not sure what I need to do to fix it. It's on a '75 350 four barrel. I took some photos if it's any help:
Attached Images
   
E.D.75GMC is offline   Reply With Quote
Old 10-17-2015, 08:25 AM   #2
Dead Parrot
Registered User
 
Join Date: Aug 2012
Location: Oklahoma City, OK
Posts: 2,599
Re: Thermostatic air cleaner isn't working

Since you have already tested the carb port, you have three things that can fail.
1. The hoses connecting it all. Replace them all, see if it works.
2. The vacuum pot on the flapper valve. Easy to test, just pull off the hose and hook a temp hose to a source of vacuum. The carb port you connect it to is good. If the pot is good, the flap should close. Perform this test while replacing the hoses.
3. The green thermostat. If everything else is good, this is your culprit. Note which hose goes where on this one, it makes a difference.

Not sure of new parts availability, especially the thermostat. I have had both the thermostat and vacuum pot fail, but at different times. Managed to find replacements for both at the local pull a part. Currently using a thermostat pulled from a mid-80s generic GM car. The style was different, (it was thinner), but the ports and spacing were the same.
Dead Parrot is offline   Reply With Quote
Old 10-17-2015, 02:49 PM   #3
rich weyand
Registered User
 
rich weyand's Avatar
 
Join Date: Apr 2014
Location: Bloomington Indiana
Posts: 1,041
Re: Thermostatic air cleaner isn't working

The correct vacuum switch for the mid-70s 350 is GM 6484244. That part number cross-references to an Echlin 2-2202. NAPA carries them
http://www.napaonline.com/Catalog/Re...Dp%3d3%26N%3d0

For a 75/76 V8, the GM part number for the vacuum motor is 6487370. For 77/78 350, the GM part number is 8994262. These are NOT easy to find. I found an old air cleaner at the junkyard. Sometimes they come up on ebay. You can also search at car-part.com. I found a bunch of compete air cleaners for 75-76 350s there.

Of course, you don't have to replace it if it's OK. You can test the vacuum motor by just hooking a line to it and sucking on it. You should be able to move the air door. If you can't, and when you suck on it, it leaks air, then it's dead.
__________________
Rich Weyand

1978 K10 RCSB DD.
rich weyand is offline   Reply With Quote
Old 10-17-2015, 05:19 PM   #4
E.D.75GMC
Registered User
 
E.D.75GMC's Avatar
 
Join Date: Aug 2013
Location: Calgary Alberta
Posts: 273
Re: Thermostatic air cleaner isn't working

Thanks for the information guys. I'll have to do a few tests tonight.
E.D.75GMC is offline   Reply With Quote
Old 11-03-2024, 04:01 PM   #5
520CheyenneK10
Registered User
 
Join Date: Oct 2013
Location: AZ Desert
Posts: 102
Re: Thermostatic air cleaner isn't working

Quote:
Originally Posted by E.D.75GMC View Post
So the flap in the air cleaner that diverts hot air from the exhaust manifold into the carburetor has stopped closing, and as such it's pulling in cold outside air on a cold start. Just in time for winter of course. I checked the vacuum line to the carb it's okay, so I'm not sure what I need to do to fix it. It's on a '75 350 four barrel. I took some photos if it's any help:

The vac. hose closest to the outside edge of the air cleaner actually goes to the flapper motor and the inside vac. hose closest to the opening that surrounds the carb. goes to the barb/tube which goes thru the choke linkage. I fixed mine by installing a new sensor, the green part in your picture, and watching with a mirror and headlamp the flapper closing at start up on a cold morning then opening when the temp reached its require degree. Part I bought eBay for $15.99 is : Buick Caddy Oldsmobile Pontiac Chevrolet air cleaner temperature sensor 6484244
__________________
2017 Infiniti QX70
2015 GMC Yukon Denali XL 4x4
1993 Jeep Wrangler YJ
1973 Chevy Cheyenne K10 4x4
520CheyenneK10 is offline   Reply With Quote
Old 11-03-2024, 07:44 PM   #6
ron350
Registered User
 
ron350's Avatar
 
Join Date: Apr 2007
Location: Birmingham AL
Posts: 266
Re: Thermostatic air cleaner isn't working

520CheyenneK10 if you know where to buy a GM 6484244 for $15 i will buy one.
__________________
Stock 75 C10 step side.
350 2 BBL, 350 trans. 150K miles.
ron350 is offline   Reply With Quote
Old 11-03-2024, 08:47 PM   #7
520CheyenneK10
Registered User
 
Join Date: Oct 2013
Location: AZ Desert
Posts: 102
Re: Thermostatic air cleaner isn't working

Quote:
Originally Posted by ron350 View Post
520CheyenneK10 if you know where to buy a GM 6484244 for $15 i will buy one.
Just bought on Ebay last week.

Seller: Noschevparts

Ebay Item Description: Buick Caddy Oldsmobile Pontiac Chevrolet air cleaner temperature sensor 6484244

My Specs:

1973 K10
SBC 350
Auto Trans.
Quadrajet 4 barrel
Stock Air Cleaner and Vacuum hose configuration
__________________
2017 Infiniti QX70
2015 GMC Yukon Denali XL 4x4
1993 Jeep Wrangler YJ
1973 Chevy Cheyenne K10 4x4
520CheyenneK10 is offline   Reply With Quote
Old 11-03-2024, 11:14 PM   #8
ron350
Registered User
 
ron350's Avatar
 
Join Date: Apr 2007
Location: Birmingham AL
Posts: 266
Re: Thermostatic air cleaner isn't working

Wow you got lucky.

Ebay says that seller is not available till 11/12/24?
__________________
Stock 75 C10 step side.
350 2 BBL, 350 trans. 150K miles.
ron350 is offline   Reply With Quote
Old 11-03-2024, 11:17 PM   #9
520CheyenneK10
Registered User
 
Join Date: Oct 2013
Location: AZ Desert
Posts: 102
Re: Thermostatic air cleaner isn't working

Quote:
Originally Posted by ron350 View Post
Wow you got lucky.

Ebay says that seller is not available till 11/12/24?
Probably just out of office/town . I have seen this before . Just save it to your watch list and hit him up after the 12th.
__________________
2017 Infiniti QX70
2015 GMC Yukon Denali XL 4x4
1993 Jeep Wrangler YJ
1973 Chevy Cheyenne K10 4x4
520CheyenneK10 is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 12:14 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com