 Inexpensive & easy heater core repair technique
The heater core in my 99 Crown Victoria developed a leak last fall. As you all know, replacing the heater core requires removal of the dashboard. Average cost is well over $1,000.00 (in my area) due to the labor to remove and reinstall the dash. Being an incorrigible do it yourselfer - I had decided to tackle this when I had a few days of slack time. Fortunately, I had not done it yet.
The other day I read that Ford had a recall due to early heater core failures, this was in the late 90s I believe. Apparently high flow rate of water was causing erosion in the core. The fix was to install a flow restrictor into the incoming line to reduce the flow. This not only reduced the water volume (and they said it also reduced the pressure but I have problems with that theory since it is inside a pressurized system) but would extend the life of the core and stop small leaks. I thought it might be worth trying on mine, but I didn't want to put it in just to find out it wouldn't work and then have to undo everything again to reinstall the bypass hose.
So I bought a 1/2" brass ball valve instead and installed it in the line. Two bonuses to this - I could simply close the valve if it didn't work, and I would also have a way of adjusting the flow incrementally, as opposed to putting in a one piece restrictor and having no flow control. It worked like a charm and cost less than $20.00. I fine tuned the setting to get the water slow enough that the leak stopped. In my case I have the valve just barely cracked open. I believe that I have restriced the flow by 95%. Given the amount of restriction I ended up with I seriously doubt if the flow restrictor part recommended by Ford would have worked in my case. Another reason to go with a valve instead.
I suspect that you could probably find a heat resistant PVC valve that would work as well, if you took the time to search it out. This fix may not work if you have a large hole or several holes, but then again maybe it will and it is cheap and easy enough to just try it to find out.
Even with that much restriction the heater still puts out every bit as much heat as it did when new and under 100% flow. I am guessing that the heater core must have so much excess capacity because of a one size fits all system, as in it will work in Fairbanks Alaska where it may need the full flow, but in Texas, apparently it only needa about 5% of the flow.
Putting the valve in is dirt easy and takes only a few minutes. All you need is a brass ball valve of appropriate size for your inflow line, two threaded brass nipples to screw into the valve threads and then slip the rubber hose over, and two hose clamps. Cut the line and insert and clamp and tune the flow thru trial. My incoming hose is 5/8" inside diameter and the nipples that fit the 1/2" ball valve go inside the hose with a perfect tight fit.
From now on I will automatically put a valve on any car I own and close the valve down down as much as possible, to extend the life of the heater core.
This is too good not to share - $20 vs $1,000 - pass it on. | 
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