Notices
86-95 Trucks & 4Runners 2nd/3rd gen pickups, and 1st/2nd gen 4Runners with IFS

22R HAI and Thermo Valve

Old 01-04-2019, 07:14 AM
  #1  
Registered User
Thread Starter
 
Join Date: Nov 2017
Location: Concord, NC
Posts: 39
Thanked 2 Times in 2 Posts
22R HAI and Thermo Valve

The HAI flapper (Air Control Valve) in the intake is stuck in "engaged" mode -- i.e., it only draws hot air from the hot-air riser, and never relaxes so that it will draw cold air from the front. The flapper itself is not stuck. If I disconnect the vacuum line from the HAI diaphragm, the flapper snaps into "normal" position. The problem is, even when the engine is at full normal operating temperature, there is still a vacuum on the line and that actuates the HAI diaphragm, which holds the flapper engaged.

Seems to me the likely possibility is that the Thermo Valve is not actuating when the temperature rises. Is there a way to test the Thermo Valve?

It can't much be the vacuum because the vacuum IS working -- to a fault! Could it be something else?

The Air Control Valve remains in this position regardless of engine temperature.
depiante is offline  
Old 01-04-2019, 10:10 PM
  #2  
Registered User
 
old87yota's Avatar
 
Join Date: Jun 2013
Location: Portland, Oregon, USA
Posts: 1,837
Thanked 75 Times in 71 Posts


What year is your 22R?

I have to agree with you that the Thermo Valve is not actuating as it should. The Automatic Hot Air Intake system is pretty simple in that it only has a few components: a vacuum supply, a Thermo Valve, a Diaphragm, and an Air Control Valve.

Since you have proven that the diaphragm and Air Control Valve is working on its own (moves up when vacuum is applied on the diaphragm and down when there is no vacuum on the diaphragm) and you have a good vacuum supply, by process of elimination the only component left is the Thermo Valve.

The only real test for the Thermo Valve is that you have vacuum at the diaphragm when the Air Cleaner temperature is below 30C (86F) and that vacuum is no longer being applied to the diaphragm when the Air Cleaner temperature is above 45C (113F).

There is not much information in my 1987 Factory Repair Manual on this system, but here is what they have:




old87yota is offline  
Old 01-05-2019, 09:50 AM
  #3  
Registered User
Thread Starter
 
Join Date: Nov 2017
Location: Concord, NC
Posts: 39
Thanked 2 Times in 2 Posts
Makes sense. I pulled my thermo valve out. Cooled it off with a stream of air. No change. Heated it with a blow dryer. No change. I would say it is shot. I was able to find a couple of used ones. Will try them out. There is no telling how long it has been defective! Gotta wonder what else in the infamous 22R Byzantine vacuum system is not working as it should!

If you have any thoughts on high-failure things I should check for, please let me know.

Thank you very much for your help.
depiante is offline  
Old 01-07-2019, 04:06 PM
  #4  
Registered User
Thread Starter
 
Join Date: Nov 2017
Location: Concord, NC
Posts: 39
Thanked 2 Times in 2 Posts
Following up:

I got another thermo valve today. It needed a good cleaning, and had to be unplugged, but once air started moving through it, it functioned properly. Calibrating it now is a little tricky, but I don't think it matters a whole lot precisely where it switches. I know when the truck starts up in an ambient temperature of 70 degrees, it is drawing hot air, and after the engine warms up, it starts drawing cool air.

No telling how long my valve was shot and it was only ever drawing hot air.
depiante is offline  
Old 01-07-2019, 08:27 PM
  #5  
Registered User
 
old87yota's Avatar
 
Join Date: Jun 2013
Location: Portland, Oregon, USA
Posts: 1,837
Thanked 75 Times in 71 Posts
Excellent!

I am glad you fixed it.

Thanks for posting a follow up!

old87yota is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
devo
86-95 Trucks & 4Runners
1
09-18-2012 03:50 PM
dj-86yota
Newbie Tech Section
2
05-19-2012 08:29 PM
BURR2OF4
Pre 84 Trucks
9
09-16-2011 11:35 AM
Steaksauce
84-85 Trucks & 4Runners
5
07-16-2008 03:24 PM


Thread Tools
Search this Thread
Quick Reply: 22R HAI and Thermo Valve


Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: