Engine Perplexing issue with heat ...

MrPerfect2

Active Member
Jul 23, 2019
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Don’t BBQ ME ! You guys have all heard about my hot temps - 225-240 degrees - so , I am going to replace radiator - I noticed when car is at 225 degrees the heat does not blow hot - guy I bought from changed thermostat and it does look like he did by the caulking - and top hose reads 230 and bottom reads 195 - so I suspect flow - what do you suggest - change rad first ?
 
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Wayne Waldrep

Before I post a pic, do you have one of yours?
15 Year Member
Apr 14, 2003
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:lol:
Got a good laugh at that first sentence!! Oh, and I promise no BBQing. As much car trouble as I've had this week, I'm not even holding any matches.
 
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John Dirks Jr

5 Year Member
Jun 28, 2013
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1) Low coolant will make the heat not blow hot. 2) The heater core could be clogged internally, just like radiators do. 3) The vacuum lines that are controlled by the buttons on the dash could be disconnected. 4) The vacuum diaphragm that opens and closes door in the heater box could be stuck or ruptured.

Thats a few things to check anyway
 

MrPerfect2

Active Member
Jul 23, 2019
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Coolant is topped off and burped - the vacuum lines on temp knob work - ( got ac and heat blows hot for a few minutes then just warm ) - the core could be clogged and I like the flap idea check - btw , how difficult is it to change heater core on 91 - thanks
 
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Olivethefet

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May 17, 2018
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how difficult is it to change heater core on 91
Not the end of the world but it SUCKS. You have to drop the dash and either cut a hole in the heater/AC box or pull the entire box out use a heat gun and other tools to open the box and replace the core. I think changing a Fox heater core is one of those "right of passage" things! I did mine less than a year ago. You can find it in my progress thread. There are some good Ytube vids on it also.
 
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Olivethefet

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May 17, 2018
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You should be able to look up at the heater box from the passenger side and see a silver vacuum module on the side of the box. I dont think its to hard to get to with everything in place.
 

Olivethefet

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May 17, 2018
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This is a pic of mine. You should be able to get it off with out much trouble.

20190210_134026.jpg


Now if the defrost quits.... well then you have to get to this one.

20190210_124541.jpg


As you can see from the location it would be very difficult to get to without dropping the dash. Thinking back on it now I should have replaced both when I had the box out of the car. :doh:
 
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Olivethefet

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May 17, 2018
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Heater cores on these cars are notorious for going out. Especially if it still has the factory unit in it. This is a pic of my old core. It was not leaking, but I was changing the AC evaporator and went ahead and ordered a new one. I'm glad I did.
20190206_221057.jpg
 

Wayne Waldrep

Before I post a pic, do you have one of yours?
15 Year Member
Apr 14, 2003
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For goodness sake, if you get a heater core get the Motorcraft one. I pulled the dash and put an LMR one in and it leaked a month later. Got another one...pulled the dash a second time and installed it (dummy) and it leaked the second it had fluid in it. So this time I did what I should have done to start with and got a Motorcraft one. I so wish I would have taken a pic of the two side by side. Think Shaq standing beside Spud Webb. No kidding, it doesn't even look like the same part. It hasn't leaked since. And just pull the whole thing out and do it right. Don't cut the box. Many people have done it i know and no offense Nick.
Since I was doing it a third time I took the opportunity to also replace the A/C evap. I also removed everything down to the firewall and cleaned and painted the metal dash frame. I also cleaned all the factory goop off the wiring that had been slowly falling in my floor for years. I rewrapped all the wiring and zip tied them in place. Hopefully, it's done for years to come.
 
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Olivethefet

Slap me as well as point and laugh
May 17, 2018
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Enterprise AL
No offense taken! Cutting out the top of the box was the only way that I knew to replace the heater core with out removing the entire box from the car. Someone had already taken the box out of my car at some point and pulled the two halves apart. It's now secured with screws. Made it a lot easier to change the core and evaporator.

I didn't know that about the LMR heater cores. I bought a kit to replace the entire AC system from www.Foxresto.com. I also brought the heater core from them. It's all aluminum. Definitely not as beefy as the one that I took out. Hopefully it doesn't start leaking anytime soon! If it does at least I know how to fix it.

20190206_224109.jpg
 

Wayne Waldrep

Before I post a pic, do you have one of yours?
15 Year Member
Apr 14, 2003
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As a good gesture to start the weekend, I won't tell you that that is the same heater core LMR sells.... :D
 

Real time recon

Mustang Master
Aug 21, 2016
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Don’t BBQ ME ! You guys have all heard about my hot temps - 225-240 degrees - so , I am going to replace radiator - I noticed when car is at 225 degrees the heat does not blow hot - guy I bought from changed thermostat and it does look like he did by the caulking - and top hose reads 230 and bottom reads 195 - so I suspect flow - what do you suggest - change rad first ?
"No BBQ-ING" lol ....some of the guys (HERE) live on BBQ other members .
 

Blown88GT

Founding Member
Nov 13, 1999
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Palm Beach Gardens, FL
Don’t BBQ ME ! You guys have all heard about my hot temps - 225-240 degrees - so , I am going to replace radiator - I noticed when car is at 225 degrees the heat does not blow hot - guy I bought from changed thermostat and it does look like he did by the caulking - and top hose reads 230 and bottom reads 195 - so I suspect flow - what do you suggest - change rad first ?
Probably needs more air flow through radiator.
Add Cobra grille insert or make your own. Or cut holes like I did.
IMG_0915.JPG
 
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