We have 2001 F-150 and our third new heater core in seven months. The last one was put in just six weeks ago. The mechanic has suggested electrolysis as the cause, but cannot tell us where it’s coming from. Any suggestions?

He mat be right or it could be a bad run of them, but I think that is less likely.

It should be able to hunt it down with a good meter and some detective work.

I should add that I would look for a bad ground, maybe the heater fan.

Isn’t electrolysis a process used for hair removal?

The mechanic seems less interested in finding the ground and has suggested that we purchase a new engine. He said that variety of metals in the engine has caused to become, over time, a battery. I think his solution is a bit extreme and not very practical. His other suggestion would be to install a brass heater core instead of an aluminum one. He said it would last about 16 months. We really don’t want to buy a new truck right now.

Why not get a second opinion?

Brass is a bad idea, IMHO, unless you want to make a battery in there. There is a TSB for electrolysis on this Ford. If your mechanic does not know about it, find a new mechanic. Electrolysis should have been checked for after the first heater core went.

Has the cooling system been maintained with the proper coolant (probably G05) for this vehicle?

Checking for electrolysis is easy. You just stick the leads from a volt meter into the coolant and onto an engine ground with the battery unhooked. If you get greater than 0.4 V replace coolant and check again. Then you hook up the battery and repeat. Next, run the engine and check again. After the engine is warmed up, check again. Check while cranking the starter. Check with all electrical accessories possible running including the cooling fan in both high an low speeds.

Note that Ford used to recommend installing a coolant flow restrictor in series with the heater core. Now they only recommend it if the leak develops in the inlet or outlet tubes, not the body of the heater core.

The old core should also be checked to see if the leak resulted from physical damage from the outside.

There are lots of web sites that discuss this problem at length. I suggest you find a radiator shop.

P.S. Is the third heater core in there or are you going to put the third one in now? The original heater core lasted 6 or 7 years. A second one could have been a bad one. Two changes in 7 months points to a change in the vehicle i.e. bad grounds. In my opinion, you should have paid for the first heater core and the rest should be free.

Cooling system has been maintained with proper coolant. All repairs have been in Ford Dealerships. The origional heater core went out in June of 2007. That unit went out again in December. The cause then was determined to be electrolosis. The repair was made free of charge with the exception of a coolant flush which was not done the first time. From what I read of several blogs I felt this was reasonable. I took the truck back for a check after 2 weeks (Dec 28th 2007) and there was no voltage reading. The mechanic said that all grounds were checked. I felt the repair was complete. Enter January 26 and again coolent in the cab. I checked the voltage across the negative terminal of the battery and the coolent and got .478 volts. Mechanic said this was due to battery leakage and that (per a ford engineer) the erosion of the heater core is caused by the coolent flowing though the engine and the dissimilar metals create a voltage which takes out the heater core. Per Ford engineering once this starts to occure the only solution is to replace the engine. but unofficially they have seen the issue corrected by replacing the heater core with a brass unit. This makes no sense to me other than the brass unit will hopefully last long enough to outlive any waranty. Top it off they want me to pay for half of the second repair. If Ford engines are only good for 160,000 miles because of coolant then I am thinking this is a good time to switch to the Toyota Tundra which I never thought I would catch myself saying. I have found no discussion on the engine becoming a Battery. I still think this is a ground issue. A second opinion is a good idea

Has someone been doing selective reading of Ford Article No. 01-15-6? It says, in part, to check for good grounds on (particularly) after-market components. The Article also says to add ground wires from the radiator to the engine and sheet metal.
Not enough people do it; but, demineralized water, or distilled water, should have been mixed with the antifreeze. The minerals in regular tap water may be increasing the electrolysis.

I would check the voltage from the negative battery terminal to the frame with the engine running, headlights and heater on to present as high of an electrical load as possible. I suspect there is a small voltage from the engine block to the chassis as a result of a bad ground cable. Voltage should be way less than 0.1V. This would cause your electrolysis if the heater core is grounded. Electrolysis is caused by a voltage potential from two different metals or external induced voltage. Unless the new engine is made from some different metal from the old one, the problem will still exist with a new engine. This isn’t the Twilight Zone, you need to talk with some more knowelegable people.

The Ford Article No. 01-15-6 states to put ground wires on the radiator. I think that it would also be appropriate to add ground wires to the heater core. It is a radiator, right?
It seems strange that in 10 years, Ford hasn’t come up with a solution to this electrolysis problem.

No, 01-15-6 has been superceded by 06-21-19 on 10/30/06. The testing procedure has been expanded. The restrictor recommendation has been, well, restricted. Model years were adjusted. Note that AC voltage should be checked with the same threshold. Very notably, Ford no longer recommends adding grounds to the heater core. In fact, this is now disrecommended IIRC, they never recommended grounds to the radiator. I never bought that anyway. Grounding the heater core or radiator always seemed like a good way to cause electrolysis in these sensitive areas by making these parts a ground path. Anyone who asked me was told that, IMHO, this was poorly thought-out advice and I have been confirmed in 06-21-19.

O.P., I think that your Ford service dept is full of something and it is not good advice. Their explanation makes no sense to me. Adding soldered brass in a cooling system designed around ferrous metals and aluminum and a particular coolant is folly without making a careful study of electrode potentials and other chemistry that I am not qualified to do. I doubt that they are qualified either.

It is possible that grounds went bad between December and January a ground went bad and chewed up your heater core. It can happen that fast, unfortunately. It is also quite possible that they did not perform the tests properly. Unfortunately there is really no way to tell. I would go back and have it replaced again unless you find a better price and you probably will not. After that, on the grounds of the crap that they gave about replacing the engine, I would not go back there unless they show you the documents that talk about replacing the engine and ?battery leakage?, or apologizes for the crap. Someone was sleeping in the Ford factory training session.

Most heater core failures, Ford or not, are probably caused by poor cooling system maintenance. I have seen a lot of recommendations that grounds be checked regularly. It is probably not a bad idea. They can go high-resistance on Toyota Tundras too. My wife had heater cores go bad in both Nissan and Honda. It was probably due to bad maintainence by former owners.

Good luck!