Go Back   Ford Mustang Forums > Mustang > 5.0 Mustang > 5.0L Tech

Welcome to our Mustang forums where Mustangers come together to hang out, discuss and enjoy their favorite Mustang hobby with fellow Mustang enthusiasts. We invite everyone to read, post, and enjoy our Mustang forum as well as the many other sections of our site.

You are currently viewing our forums as a guest. By joining our community you gain access to post topics, communicate with members, upload your photos and access many other special features. Registration is fast, simple and free so why wait, join our Mustang community today! If you have any problems with registration or your account login, please contact support.

5.0 Mustangs Tech Forum

5.0L Talk | 5.0L Tech | 94-95 Tech | 1979-1993   1994   1995   Upload Pictures | Timeslips | Power Adders | Mustang Tech 


Reply   Post New Thread
Unread 11-17-2004   #16 (permalink)
Snake1 is offline Banned

5.0L Member


Joined: Dec 2003
Posts: 66 Threads: 40
 Snake1's Country Flag  View Snake1's 109 photos
Alabama
Snake1 is on a distinguished road
Default

Fox Body Mustang (1984-1993) Heater Core Replacement Documentation

The following documentation is a report of my experiences in the world of 5.0 heater cores. Specifically, it included the history of my experiences and most importantly, how to change that heater core WITHOUT discharging your air conditioning, dispelling much false information out there on the subject! This is especially important these days with the astronomical prices of R12 and R12 system service. This document covers the 1985 GT 5.0 and the 1990 LX 5.0 models. Keep in mind that your model may be very similar if not exactly the same. A good amount of information contained in this document applies to the 1982-1993 model year 5.0 Mustangs.

Have you experienced the 'Green Pool of Death' or have you succumbed to constant fog on the right hand side of the windshield? If so your car probably has a ruptured heater core. I'm sure that you have heard all of the horror stories about changing this little headache out. I was quoted from a local Ford dealer that he would happily charge about $700 for the job. If this doesn't sound like much money to you, then stop reading this now, take your car down to the local Ford dealer and lay the headaches on them! Well, as for me, I'm very reluctant to part with that $700, so I'll do it myself, thank you.

I have done about six heater cores in Fox-3 Mustangs over the past eight years. So I consider myself somewhat of an expert on the subject.

My experience in late model Mustang heater core replacement started on my 1985 GT 5 speed back in about 1990 when I observed the green pool of death and a continuous foggy haze on the right hand side of the windshield. So I began to attack the heater core project just like everyone had recommended, including removing the entire dashboard, and discharging the air conditioning system to remove the evaporator case from the firewall. And after much perspiration persistence, I installed the last screw in the glove box and fired the engine. The heater worked great, and no leaks! Sadly enough, this was not the end of the story. I did this horrible job four more times. Each core only lasting somewhere between six weeks to a year. It didn't seem to matter if I used an off brand core or got one directly from a dealership. Why were these failing? Ahhh, what I needed was the police special service part heater core flow restrictor. So I made one and installed it. It was an aluminum standoff with a 0.25" hole drilled through the center of it. More details on that later.

The cores still failed. While I installed the last core in that car, I made a very important observation. When I was closing the heater core cover with the two self-tapping screws, I heard a sound, like that of thin metal wrinkling. At this point I began to theorize why these heater cores fail.

There are two reasons that heater cores fail in Fox-3 Mustangs:

The first reason is normal wear and tear associated with thermal cycling. You can expect a new, factory installed (not dealer!) core to last between 5 and 6 years before it will start seeping coolant. This is given a 5.0L engine and the normal hard driving/abuses that this class of car is put through.
The second reason that heater cores fail is purely mechanical. At the factory, the cores are installed in the cases with a black gooey sealant called dumb gum. Over the years, the sealant gets hard. Not hard like a brick, but hard enough that when you install a new core in the same location as the old core, the sealant will not conform to the slightly different shape of the new core. I'm not saying that the cores are dimensionally different, but the fins that make up the water passages, being in a zigzag pattern, are invariably in a slightly offset position, requiring that the sealant be displaced in a different pattern. What I recommend is that it is ESSENTIAL to remove ALL of the black sealant BEFORE installing the new core! Unless of course, you enjoy this job and want to do it again. If you must use a sealant when re-assembling the heater core cover, I recommend Dow Corning RTV 3140. RTV 3140 is a silicone coating used in the electronics & aerospace industries because it is very lightweight and flowable. 3140's flowability will avoid any distortion or flexing of the new core when the cover is tightened, ONLY IF THE OLD BLACK SEALANT IS REMOVED! Remember, REMOVING THE OLD BLACK SEALANT IS CRUCIAL!
The most recent heater core job that I did was in my '90 LX 5.0 5 speed when it hit 66K miles last February. I did the whole job with the A/C completely connected!

The trick to it is to get everything loosened up, and REMOVE the bracket off of the A/C accumulator (engine_c.jpg). This will allow enough freedom to get the evaporator case away from the firewall about one inch. It's very difficult and a royal pain, but you'll need to remove the two 5/16 self-tapping screws that hold the core cover in place. I used an small ignition wrench to remove the screws. With everything loose and the dash propped up (drvrs_v.jpg) and away from the windshield, you can open the core cover and remove the old core (removal.jpg). Removing the old core without damaging it is a good test to determine if you can install the new core without damaging it, so keep that in mind. It is crucial in this procedure to prop the core cover and the dash up out of the way so you can work (detail_1.jpg). I used a large socket and a 1/2 drive extension (detail_2.jpg) to hold the cover open (dashview.jpg) to extract the old core and install the new one without tweaking it (very important.) Before installing the new core, I painstakingly cleaned, with surgical precision, the old black goo sealant that seated the old core (install.jpg). By far, the most difficult task of the entire job is getting the new core's tubes lined up with the gasket and holes in the firewall. On my car this step took the longest of any single step in the entire job. But don't despair, get a helper and with one person maneuvering the case on the inside and one person on the outside steering the lines to their propper place, you will get it, it just takes time!

How do you make the flow restrictors? I made them from 5/8 OD aluminum stand-offs drilled to 0.25" ID (restrict.jpg). The heater seems to be effective but the motor has to be good and hot for the heater to be _really_ hot. I can live with this, but if I were to do it again, I might consider a 3/8 ID. After about 20 minutes of normal driving, I observed air temperature of 157F. This is with a 192F thermostat. When installing the heater core restrictor, make sure that it goes in the input or pressure side. The input/pressure side is the top metal tube that runs along the intake and the larger of the two pipes on the heater core.

With improved clearance in the core compartment and the restrictor plug that I machined, installed, I hope to see at least 66K miles out of this one.
Snake1 is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Sponsored Links
Advertisement
 
Unread 11-17-2004   #17 (permalink)
Stangboy5666 is offline Made Member

5.0L Member


Joined: Oct 2003
Posts: 1,263 Threads: 178
 Stangboy5666's Country Flag  View Stangboy5666's 11 photos
Seattle   Washington
Stangboy5666 is on a distinguished road
Default

Thanks guys
__________________
Cardinal Red '88 GT 5 speed, 99 Contour Electric Dual Fans, Battery relocated, 130 amp alternator, 76mm Mass Air conversion, 75mm BBK throttle body, 5.0L .030 over, BBK SSI, AFR 185cc heads, Comp Cams XE276HR, BBK ceramic longtubes, Spec Stage II clutch, MM front/rear coil overs, MM front LCA's, MM manual brake conversion, Flaming River Manual Rack, 94-04 Cobra front brakes, 99 Cobra IRS, Torsen T2R differential, 3:55 gears
Stangboy5666 is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Unread 11-18-2004   #18 (permalink)
scott88gt is offline Rookie


Joined: Jun 2004
Posts: 10 Threads: 0
 scott88gt's Country Flag
Davenport   Washington
scott88gt is on a distinguished road
Default

[HTML]http://www.mustangmonthly.com/howto/5652/[/HTML]

Here's the link snake was talking about. I just did it to my 88 and got her done in short time (5 hrs with beer breaks )

BTW--Thanks Snake for posting this on the other site!!!!

-Scott
__________________
1965 Fairlane Sportscoupe (289--TRW, Crane, Holley Etc.)
1988 Canadian Mustang GT (306--MAF Conversion, Edelbrock Heads, SRP, Scat, #24 inj, 73mm MAF, 65 TB, Erson Cam--work in progress, next up traction!!!!!)
scott88gt is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Unread 11-19-2004   #19 (permalink)
Sun5.0 is offline Rookie


Joined: Nov 2004
Posts: 2 Threads: 1
Sun5.0 is on a distinguished road
Default

hey how is it going i'm new on this forum and i can't find out where to post messages on the board
Sun5.0 is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Unread 11-19-2004   #20 (permalink)
Stangboy5666 is offline Made Member

5.0L Member


Joined: Oct 2003
Posts: 1,263 Threads: 178
 Stangboy5666's Country Flag  View Stangboy5666's 11 photos
Seattle   Washington
Stangboy5666 is on a distinguished road
Default

Go to the main screen of 5.0L tech, and look at the top left of all the posts, you will find a gray button that says new, click on it, and you can start a new topic, dont forget to give it title.
__________________
Cardinal Red '88 GT 5 speed, 99 Contour Electric Dual Fans, Battery relocated, 130 amp alternator, 76mm Mass Air conversion, 75mm BBK throttle body, 5.0L .030 over, BBK SSI, AFR 185cc heads, Comp Cams XE276HR, BBK ceramic longtubes, Spec Stage II clutch, MM front/rear coil overs, MM front LCA's, MM manual brake conversion, Flaming River Manual Rack, 94-04 Cobra front brakes, 99 Cobra IRS, Torsen T2R differential, 3:55 gears
Stangboy5666 is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Unread 11-19-2004   #21 (permalink)
GhostDog 5.0 is offline Top Dog

5.0L Member


Joined: Aug 2002
Posts: 4,844 Threads: 164
 GhostDog 5.0's Country Flag  View GhostDog 5.0's 20 photos  View GhostDog 5.0's HomePage
Edinburg   Texas
GhostDog 5.0 is on a distinguished road
Send a message via AIM to GhostDog 5.0 Send a message via Yahoo to GhostDog 5.0
Default

Quote:
Originally Posted by Stangboy5666
Go to the main screen of 5.0L tech, and look at the top left of all the posts, you will find a gray button that says new, click on it, and you can start a new topic, dont forget to give it title.
Or I'll fix it
__________________
89 GT Hatch: Custom M90 Supercharged w/ Ported Trickflow Trackheat Heads, Stage 1 cam, Streetheat lower / Sheet metal upper, Tweecer RT & PLX Wideband, 75mm TB, 1.6 Roller rockers, 3.73s, MSD 6a, Canton 7qt Pan+ Windage tray, 36LB Injectors, 200 amp Alternator, 75mm Pro-Mas MAF, 190lph fuel pump,Spec Stage 1 Clutch,SouthSide LCA's, Pro 5.0 Shifter, Steeda CC Plates / Springs, FMS Aluminum Driveshaft, New T5 w/ 2.95 first gear, Underdrive pullies, Zirgo 3300Cfm Elec. Fan, AFCO alum. radiator
GhostDog 5.0 is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Unread 11-19-2004   #22 (permalink)
Stangboy5666 is offline Made Member

5.0L Member


Joined: Oct 2003
Posts: 1,263 Threads: 178
 Stangboy5666's Country Flag  View Stangboy5666's 11 photos
Seattle   Washington
Stangboy5666 is on a distinguished road
Default

oic what was going on, nevermind... good job Freddy
__________________
Cardinal Red '88 GT 5 speed, 99 Contour Electric Dual Fans, Battery relocated, 130 amp alternator, 76mm Mass Air conversion, 75mm BBK throttle body, 5.0L .030 over, BBK SSI, AFR 185cc heads, Comp Cams XE276HR, BBK ceramic longtubes, Spec Stage II clutch, MM front/rear coil overs, MM front LCA's, MM manual brake conversion, Flaming River Manual Rack, 94-04 Cobra front brakes, 99 Cobra IRS, Torsen T2R differential, 3:55 gears
Stangboy5666 is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiTweet this Post!
Reply With Quote
Sponsored Links
Advertisement
 
Reply   Post New Thread



Thread Tools



Mustang Photos
Mustang Links    Top Sites    RSS    Link To Us    Add to Favorites    Archive    Terms of Use    Site Rules    Privacy    Contact    Sponsors    Advertise   
AllFordMustangs is not affiliated with or endorsed by Ford Motor Company. ©Copyright 2002-2011 All Auto Enthusiasts Network

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162