cpnmark1

I just purchased a 1991 Ford Mustang LX convertible with a 4 cylinder engine and automatic transmission.

It has 60k original miles on it. I live in the Dallas, Texas (that could be important due to the problem I am experiencing).

I have about a 25 mile one-way commute. The car was over-heating so I replaced the thermostat. That has seemed to only mildly help. The car's temperature now hits the top of the "normal" zone but hasn't overheated (hit the red bar) yet.

Do these year models with the 4 cylinder engines have a history of running "hot"?

Is it just because I live in Texas and it is 100 degrees outside?

Also, my a/c blows VERY COLD until I get about a mile from home (also when the temp gauge is pretty hot). I am not sure if this is related.

Any thoughts from other 91 4cyl LX owners?

Thanks,
Mark

mikerp76

is your rad fan turning on? if not it could be a realy or the fan switch or the fan itself has failed.

cpnmark1

Ya, it is working

theboss302

This is how Haynes manual says to trouble shoot overheating.

1. Insufficient coolant in the system
2. Water pump drive belt defective or not adjusted properly
3. Radiator core blocked or radiator grille dirty and restricted
4. Faulty thermostat
5. Fan blades broken or cracked
6. Radiator cap not maintaining proper pressure
7. Incorrect ignition timing

Good Luck

cpnmark1

I changed the thermostat (cost about $10) and still runs hot. I also removed it and car is still overheating. I also saw this morning after my commute, water leaking from a hole on the passenger side of the firewall. Wasn't sure if that was just the a/c drain.

I don't have a thermometer (outside of the one on the vehicle). I'm wondering if it is the radiator.

I'm not sure what else to check for outside of taking it to the dealership for them to diagnose.

mikerp76

you may need to bypass your heater core. is is a steady drip or is it pouring out while the engine is running. also is it dripping with the a/c off as well. if you have to bypass the heater core you will need 2 90* fittings and some hose if your fan switch is mounted on the hose near the heater core.

cpnmark1

Mike-

It is a steady drip. It does not seem to be dripping as bad with the a/c off.

Will bypassing the heater core do any damage?

How would I bypass the heater core? I've never done anything like that. Do you know of a youtube video?

Thanks,
Mark

mikerp76

by passing the heater core won't hurt anything and is easier than replacing it. you will need 2 90* hose connectors and a foot of heater hose. disconnect the hoses from the heater core and insert the 2 90 into them and insrt a small section of heater hose in between them and you are done. just be sure to leave the fan switch on the hose as with out it your fan won't work.

bl817

check and make sure your radiator is not plugged (bugs/leaves/etc) i replaced mine with a new one (86 bucks) from the local parts store and my car runs noticeably cooler.