Mustangs List FAQ - Part 4

"Late Model" MUSTANGS MAILING LIST FAQ - PART 4A, Version 1.0
Last updated 4/13/95.

NOTE:  The information in this document is correct to the best of the
author's knowledge.  However,  due to a change in employers the author will
not be able to update/correct this document in the future.  The author
accepts no responsibility for any damage, injury, or other "loss" you
encounter while working on your car.

This portion of the FAQ was written by Andre Molyneux.  It's labeled as
Part 4A, as my intention was to make part 4 of the FAQ contain common
failures and fixes.  This obviously would get too long to handle in a
single section, so I planned to do Part 4A, 4B, 4C, etc.  Anyone adding on
to the FAQ in the future may want to keep the same naming convention.


                        Part 4 - Common failures/fixes
               Section A - Engine cooling system/heater core


=====================================================================
1) Failures/diagnoses
=====================================================================

The cooling system is a known trouble spot on Mustangs.  Water pumps and
heater cores go out with distressing regularity.  Some of the more common
problem symptoms/causes are:

	- Coolant dripping/spraying from underneath the water pump.
	    Most likely a water pump/gasket failure.  See section 2.

	- Coolant overflows into catch tank even though car hasn't over-
	  heated, and the radiator is low when checked.  
	  - Radiator cap is bad.  Have it pressure tested.  Stock caps
	    are set for 16 psi.
	  - Bad head gasket.  Exhaust gasses are getting into the cooling
	    system and forcing the coolant out.  Replace head gasket.

	- Antifreeze smell in passenger compartment.
	  - Bad heater core.  See section 3.

	- Defroster fogs up the inside of the window instead of clearing
	  it.
	  - Bad heater core.  See section 3.

	- Carpet under passenger-side dash is wet
	  - Bad heater core.  See section 3.
	  - Windshield gasket seal is bad.


=====================================================================
2) Water pump
=====================================================================

The water pump write up only covers 5.0L cars at this time.

The water pump is a consumable on 5.0L Mustangs.  Expect it to go out
around every 50k miles or so, although some certainly go sooner and others
last much longer.  Fortunately the water pump isn't too difficult to
replace.  The replacement procedure in the factory manual is pretty decent,
so only a few additional hints will be added here.

How it fails:

There are two main failure modes for the water pump, which can be diagnosed
by where the coolant is leaking from.  They are:

	- Input shaft seal failure
	  The seal around the input shaft between the pulley/fan and
	  the impeller (inside the pump body) starts to leak.  This
	  failure mode results in coolant leaking out of a "weep hole"
	  on the underside of the pump housing.

	- Gasket failure.
	  The gasket between the pump housing and the thin plate on the
	  backside of the pump fails.  This plate is sandwiched between the
	  pump housing and a raised ridge on the block, except at the
	  bottom where there's a gap in the ridge.  The failure almost
	  always occurs at this point at the bottom of the pump.

Both failures will result in coolant leaking from the underside of the
pump.  If the gasket has failed, you'll see coolant spraying out from the
pump/engine block junction.  Input shaft seal failures typically don't
spray as high a volume of coolant out, and it will be coming from further
forward on the pump body, where it tapers down around the shaft.

Input shaft failure requires replacement of the pump.  For gasket failures
you can just replace the gasket, but based on the age of the pump you may
want to go ahead and replace the whole thing anyway.  If the pump's already
got 50k miles or more on it, it doesn't make much sense to replace just the
gasket when an input shaft seal failure probably isn't too much further
down the road.

Getting a replacement:

Unfortunately, getting the correct pump isn't always easy.  Since the
5.0/302 has been around for a long time, there have been a variety of
sublty different pump designs used over the years.  This is complicated by
the fact that later cars with a single serpentine-belt spin the pump in the
opposite direction compared to earlier cars.  It's not at all unusual for a
store to give you the wrong pump for your application.

Although it's a pain, you should pull the old pump off the car before
heading for the auto parts store.  Things to check when comparing the old
pump and the new pump:

	- Verify that the spacing of the holes for attaching the fan
	  line up correctly (otherwise you'll get the whole thing put
	  back together and discover you can't bolt the fan back on).
	- Make sure that backing plate of the new pump doesn't have any
	  protrusions that extend further back than the old pump (or
	  else it won't seat on the block).
	- Verify that the impeller blades are oriented the same direction
	  on the new pump (otherwise the pump will be trying to move
	  coolant in the wrong direction - it'll bolt up, but you'll
	  encounter major overheating problems in short order).

Several people have commented about problems with rebuilt pumps.  Brand new
pumps aren't overly expensive, and are probably worth the money.

Special tools:

Replacing the pump doesn't take anything special (aside from a 5/8" deep
socket, which is an absolute necessity).  A well-stocked socket set, a
tube of sealant, and a scraper are about all that's required.

Hints:

Since you're draining most of the coolant and disconnecting one of the
hoses anyway, you might want to go ahead and pull the radiator when doing
this job.  It's very easy to do, and getting it and the fan shroud out of
the way gives you a lot more elbow room.

The pump-to-thermostat hose is a pain to get on and off.  Remove all of the
other necessary hoses before unbolting the pump, but leave this hose until
you actually have the pump unbolted from the block.  The hose comes off
easily when you can move the pump around.  Likewise, install this hose onto
the new pump before bolting it up.

=====================================================================
3) Heater core
=====================================================================

The heater core is a well known weak-spot on Fox Mustangs.  In fact, a
local radiator shop claims that replacing the heater cores in Mustangs (as
well as Taurus's and T-birds) is what keeps them in business.  The
information in this section applies to '79 to '93 Mustangs - I don't know
if Ford changed the design of the heater core and/or evap case for the '94
and later cars.

Failures are typically pinhole leaks along the seams where the core was
soldered.  However, some people have damaged their cores by flexing the
input and output tubes while replacing the heater hoses.  Take your time
and be careful when replacing these hoses - creating a stress-fracture on
the core is a very expensive mistake.

The core itself is relatively inexpensive, but replacing it can be quite
difficult.  In most cases, the dash has to be pulled back, and if you have
A/C the manual says you have to discharge it before pulling the core.
However, a number of people have managed to replace the core in cars with
A/C without discharging - it can be done, but it's not easy.

On earlier cars without A/C, heater core replacement can be very easy.
Simply remove the glove-box door, and look for a removable panel on the
heater case.  If you've got one of these, all you have to do is remove the
panel and you've got access to the core.  Unfortunately, this only applies
to cars without A/C, and only up to maybe the mid-eighties.  Later non A/C
equipped cars (and apparently all A/C equipped cars) require that the
dashboard be pulled back, and that the heater/evap case be pulled back as
well, to get at the core.

You really need the factory manual for this job, as it clearly calls out
the location of all the fasteners that must be removed in order to pull the
dash back.  Once you've managed to get the dash pulled back about 8 inches
or so, you'll have a good look at the evaporator case.  The problem with
accessing the core is that the access panel has to be pulled off from the
top, but the evap case is tucked under structural metal.  Doing the job
"right" would involve pulling the evap case back about 6 inches, but the
A/C lines prevent this - thus the instructions tell you to discharge the
A/C system and disconnect the lines.

The case can be pulled back a little bit before the A/C blocks further
progress.  This is just enough that with some prying (and perhaps a little
bit of judicious cutting of the plastic case) that you can pull the old
core out of the case.  You need to be very careful when inserting the new
core - you don't want to rub it hard against the case, or get it jammed and
have to force it in, as you could damage it and end up with a brand new
leaking core.  Cutting the case (and using some sealant to patch it up
afterwards) is much preferable to risking any damage to the core.

When you install a new core, make sure that is has a plastic restrictor on
the inlet (the core may come with this, or your old core may have one that
you can re-use).  If you don't have one, get one from a radiator shop or
other source.  You need one because the Mustang's heater core's inlet is
larger than its outlet.  This means that a pressure drop is created across
the core, and this is probably one of the reasons why they fail so often.
Adding an inlect restrictor causes the pressure drop to occur before the
core, and will hopefully lead to a longer life.  Ford started putting the
inlet restrictors on sometime in the mid-late eighties, but it's a good
idea for any year of car.

END OF MUSTANGS MAILING LIST FAQ - PART 4

Copyright and Attribution

These files are intended for the private use of late model Mustang
enthusiasts.  Much of their content was contributed by subscribers to
the Mustangs mailing list, and such material is attributed to the
original source wherever possible.  However, as the maintainer of this
directory, I bear sole responsibility for its content.  I welcome
corrections and additions.

If you've come here to locate a repair procedure that's covered in the
Ford shop manual, you won't find it.  This is because I don't have room
for an online repair manual, nor do I have the time to type it in, nor
could I hope to do as good a job as the authors of the existing manuals.
The intent of this directory is to provide pointers to existing
resources, and folklore and tips that you won't find in the literature.

CONTENTS:

Are currently limited to fog light repairs and part 1 of the FAQ proper.
More parts of the FAQ are under development, and will be added in the
near future.

COMMENTS, CORRECTIONS, ETC.:

Should be sent to chucko@chucko.com.  Corrections and additions will be
incorporated at my earliest convenience.

CREDITS:

I wish I could remember everyone who's helped put this together!  If
you've contributed something, I apologize in advance if your name is not
mentioned here.  Two names that stand out are Andre Molyneux for
actually editing the initial version of the FAQ, and Gary Gitzen for
establishing and maintaining the Mustangs mailing list.

COPYRIGHT NOTICE: 

Entire contents of this directory compilation copyright (c) 1994, Chuck
Fry, et al.  Other individual copyrights apply as indicated.
Reproduction for profit without prior permission is prohibited.
Distribution for private use in any form is expressly permitted,
provided proper attribution is given.  This notice will be replaced by
the real copyright notice when it exists.

DISCLAIMERS: 

While the information presented here is correct to the best of my
knowledge, I disclaim all responsibility and liability for its use.  I
will gladly correct any information found to be erroneous at my earliest
opportunity.

Be aware that some of the modifications, procedures, and driving
techniques described here may be dangerous, and take appropriate safety
precautions.  Save the high-speed antics for the race track, where you
have a chance of surviving a mistake.

The opinions expressed here are the personal opinions of the individual
contributors, and do not represent the official opinion or policies of
any organization, least of all Best Internet Communications or Ford
Motor Company.

 -- Chuck Fry  chucko@chucko.com