osu

I replaced my heater core about 8 months ago and it started leaking again after3 months. Replaced it again and I just noticed it is leaking water again out of the drain hole in the firewall. Anyone had this happen to them? I have 1996 Saleen Mustang 4.6 2v that is stock. The first heater core was aftermarket the second one was Ford OE. Luckily I run a parts warehouse and my customers replace the cores inexpensively but I'm getting tired of having it done. I do know that a leaking head gasket can cause a radiator to split the tanks but I never heard of it splitting a heater core. The last heater core was leaking along the tank lines. Thanks for the Help

undecided.steve

Dumb question, but are you sure it's the heater core and not the normal A/C evaporator condensation?
IOW is the fluid green (antifreeze).

Assuming yes, here are some things to check:

1. Electrolysis Look here: http://www.4s.com/fourseasons/tech_tips/TOP10.pdf
2. If the hose has a restrictor in it are you certain it was put back? (Not sure if Ford has one in their hoses)
3. Head gasket leaking slightly on the exhaust side causing excessive pressure in the system.

contentsunderpressur

+1 You hit the nail on the head here. If your other heater cores had small pin holes the you really need to look into the electrolysis. I changed 4 core in two months in a customers F 150 at the dealership and they all had little pin holes in them. It was electrolysis, I had to run a ground wire from the inlet and outlet lines to the heater core (from the aluminum part not the rubber,duh) and flush the cooling system to solve the problem.

osu

I wish it was A/C condensation, but sadly to say it's green. Thanks for the tech bulletin from 4 seasons. I would really like to believe it's electrolysis, but the system was completely flushed both times. I'm afraid it may be a head gasket leaking. I bypassed the heater core so I could drive it. I also noticed that the core seems tostart leaking only after I get on it a little. I rarely take it above 4,000 RPM but I have taken it over 5 when I need to get into traffic. I'm going to have one of the shops do a test for a bad head gasket and see what comes out. If I have to replace the head gasket it may be time to spend the money for PI heads. The car only has 49,000 miles on it but I'm thinking it probably is the head gasket

osu

Boy, You've given me new hope that maybe it is electrolysis. If you had to change four on a F150. I'll try your solution and see if it helps. I don't know if my customer wants to even see this thing again after replacing two of these. Everyone knows how much fun these are to replace. I'm thinking of taken it to Ford and just paying to have it done. They may have already done the same thing that you did and have a solution.

contentsunderpressur

Before you pay to put another heater core in have it checked for a head gasket. It's really easy to check for a head gasket. You don't want to change it again and it bust another one.