AMGBA website home page or AMGBA Photo Gallery or AMGBA Club Blog
Subscribe in a reader


Join or renew today and receive a free t-shirt or tech CD, see details in the join the club section at www.mgclub.org!

Author Topic: heat coming from bottom of drivers seat firewall  (Read 214 times)

0 Members and 1 Guest are viewing this topic.

june2021

  • An AMGBA Club Member
  • ***
  • Posts: 25
heat coming from bottom of drivers seat firewall
« on: May 27, 2021, 01:07:07 PM »
I have a 1974 MGB. Heat comes blasting from somewhere on the drivers side near the feet. All vents are closed but yet the hot air still comes through. Any suggestions on why and how to stop?

Art

  • chfwrench
  • AMGBA Club Tech Staff
  • ****
  • Posts: 285
  • Membership Number (if known): 91-10014
  • MG information: '73 red B roadster
Re: heat coming from bottom of drivers seat firewall
« Reply #1 on: May 28, 2021, 08:39:01 AM »
First thing to check is if the heater valve (ref. Moss P/N 360-410) is closed and sealing. 

Sometimes the control cable slips and doesn't close it all the way or the internal gasket or seat inside the valve body deteriorate and no longer seal properly, so you get a constant hot coolant flow to the heater as if the valve were open. 

Those 'flap vents' on the heater never really seal completely, so there's always some air flow through them from the vent as you are moving, even with the fan off.  Heat would likely come through the small duct vent on the drive tunnel just alongside the gas pedal.  Goes right on your feet, so can really warm things up.  When stop driving, the airflow stops.  The fix is to replace the valve.  Cheap and easy to do, so might be warranted, even if you can't determine if that's the problem.

Also I'd check the firewall plug just above the pedal.  It's a fairly large rubber cap (ref Moss P/N 282-970) just above the brake and clutch pedals in front of the brake and clutch master cylinders.  Same deal - air flows only when you move and it's all from the engine compartment, so hot.  It just pops into place and can partially open or fall out entirely.  Easy fix to reinstall or replace if missing.

Those are the simple ones.  Let me know how you make out.  Hope that helps.

Safety Fast!

Art

 
Art Isaacs
AMGBA Tech Staff
chfwrench@aol.com

june2021

  • An AMGBA Club Member
  • ***
  • Posts: 25
Re: heat coming from bottom of drivers seat firewall
« Reply #2 on: May 28, 2021, 08:44:51 AM »
thanks Art! I will check this out and let you know.
Brian

june2021

  • An AMGBA Club Member
  • ***
  • Posts: 25
Re: heat coming from bottom of drivers seat firewall
« Reply #3 on: June 02, 2021, 03:23:51 PM »
Art, you nailed, of course. It was a heater valve that would not seal. Replaced and all done! Thanks too for always indicating the Moss Auto part numbers too.
Brian

Art

  • chfwrench
  • AMGBA Club Tech Staff
  • ****
  • Posts: 285
  • Membership Number (if known): 91-10014
  • MG information: '73 red B roadster
Re: heat coming from bottom of drivers seat firewall
« Reply #4 on: June 03, 2021, 08:26:01 AM »
Hi Brian,

Very good.  Glad I could help!

Hope to see you on the road sometime.

Safety Fast!

Art
Art Isaacs
AMGBA Tech Staff
chfwrench@aol.com


 

   AMGBA website home page or AMGBA Photo Gallery or AMGBA Club Blog