"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 AttributionThese 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 email@example.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 firstname.lastname@example.org
Mustangs List FAQ - Part 4
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