Gun Jam

I keep damaging heater cores to the point where they develop a pin hole leak after about a year or 2.

The old cores bulged on the top and bottom slightly and its becoming apparent that they are the best core I can get and pressure is too high for them still

so my plan is to install a single ball valve on the inlet line. This is the line that runs from the water pump to the core

The return line runs from the core to the intake manifold just behind the thermostat.


If I restrict water flow from the intlet line this is going to reduce pressure to the core correct? Lets say the valve was shut off on the inlet then the pressure acting on the core would be equal to that of the pressure just behind the T stat on the intake manifold side right? This would also be equal to the pressure inside the radiator right? And this cant exceed 13 pounds because of the 13lbs cap im running right?

If I can reduce core pressure to something closer to rad pressure I should be fine. I used my compressor to abuse the dead core and at 40 pounds it was not enough to further damage or increase swelling on the top and bottom faces. I suspect pressure acting on that core to be exceeding 40 PSI in some case (6200 RPM WOT)

So if the exit hole from the core going to behind the T stat is larger than the incoming hole (thanks to the valve) then pressure should be less.

Is this a solid idea?
and better ideas?

08'MustangDude

Found this at another forum:
You could also run a bypass to reduce pressure.

Install a "Y" in the hose after the pump that goes to the core.
Install a "Y" from the core to the return hose.
Run your bypass hose from one end of the "Y" to the other.

So, you have two paths for the coolant, one a direct bypass, and the
other to the heater core. The heater core is also on a bypass, so
adding another one will reduce the pressure to the core.

Or, install a reducer on the pump to heater core hose.

You have options...

Gun Jam

Yes the Y was something I had considered but opted to restrict the flow because I run the hoses next to each other along the intake and there isnt enough room to install a bypass between the to hoses that would fit nice

Worth1

OK, your way off, #1 water flows from the intake manifold to the water pump. #2 the water pump doesn't make enough head pressure to blow your nose, let alone bulge the heater tanks. If your tanks are bulging, your radiator cap is holding too much pressure, or you don't have enough antifreeze and the coolant is freezing and expanding the tank. And you can trust me on this, I owned a Radiator shop for 20 years.

08'MustangDude

I have been reading, and read more than one incident where people are blowing heater cores
at high RPMs. I know what you're saying, thought the same thing, but after reading more
incidents, and people installing reducers FIXING the issue, there has to be something to it.

Worth1

I've owned everything from a '65 VW bus to a '69 428CJ, beat the crap out of most of them, and have never bulged the tank on a radiator or a heater core. But if you think a restrictor will help, put it in the hose from the intake manifold to the core.

08'MustangDude

I have never had one blow either, but I am reading it about the Mustangs...

AND, ford does have a bulletin out about repeat heater core failures, but do not
see the Mustang in that list...ISSUE:

The majority of repeat heater core leaks are due to high flow rate or use of poor quality coolant.
However, electrolysis should also be checked, especially when repeat repairs have occurred.SERVICE PROCEDURE

1. Review the location of the leakage and check the condition of the coolant:
   1. If leaks are found on the inlet (or outlet) tubes entering /exiting the heater core, it is most likely due to due to high flow rate - replace the heater core and install a restrictor in the heater hose closest to the engine block, reference Workshop Manual, Section 412.
   2. If leaks are found in the body of the heater core itself, and does not appear to be the result of physical damage like contact or puncture, check the coolant for possible electrolysis.

SO, they know there is an issue, they just don't see a plague of them with the Mustang to
update the TSB to include it.

Electrolysis is too much voltage from grounds, in the coolant system.

A Ford bulletin on basically the same subject was blunt, “Do Not Ground Heater Core. If the heater core is
grounded, you have provided the electrolysis a path through the heater core. This would cause the heater core
to become an anode or receiver, and it would promote the electrolysis, or any stray voltage, to use the coolant
as the ground path.”

Electrolysis is possible with a voltage reading of 0.4 or higher, taken with the voltmeter negative lead grounded
to the battery and the positive lead suspended in coolant.

Worth1

nowhere in that bulletin does it mention an expanded tank, they are talking about heater tube to tank connections, and core leaks, which both show up as white deposits where the leak is.

08'MustangDude

Well, it is happening, if you would search yahoo on mustang heater core failures...

Gun Jam

You can see the top of the photo there is a slight bulge on the heater core the new ones are much flatter as in flat

Ok so I need you to explain to me how the water pump is return and the intake in In let.

My reasoning is: The manifold is RETURN because its fitting is right behind the T stat. The T stat dumps into the top of the radiator this is hot water that has made its way through the system and is fixing to have heat removed from it by the radiator as it moves down to the lower rad hose.

The pump is Inlet because its pulling from the lower hose and is forcing cool(er) water into things like the block and heater core PLUS that fitting appears to be right off the impeller housing this really appears to be the high pressure side of things. If I can reduce the volume of water on the high pressure side then it will reduce pressure to the core because the exit hole of the core (that fitting that dumps behind the T stat) would be larger. I would think that would reduce the violence that is being placed on the core.

Yes its real issue. I run a high volume pump because I cant find quality standard pumps (all GMB or re- badged GMB good for 1 year). The crap cores last 3 to 6 months the better cores may last 1.5 to 2 years.

I would like your ideas on why I should be reducing volume on the intake side... Wouldnt that make things even worse. Now wouldn't it have full pressure from the pump side with little or no exit volume? A deadhead pump situation with the core in the middle??

I run a 13Lb cap (stock I think) and 190 to 195F water temp

Thanks guys!!
-Gun