Rear head cooling mod [Archive] - MercuryMarauder.net Forums

Logizyme

12-08-2015, 09:30 PM

The issue is a lack of flow around the backside of cylinders 4 and 8. This causes the rear of the cylinders to run hotter than the rest and more prone to failure. Most modular engines supply coolant to the heater core by way of a fitting installed on the rear of the passenger side cylinder head, which promotes flow around the backside of cylinder 4. The drivers side head almost never has factory fittings and thus caused #8 to be the most common to overheating related issues. In the case of the Marauder, heater core coolant is supplies by a fitting on the coolant cross over tube at the front of the engine, and neither cylinder head has desirable flow around the backside. On the 4.6 4v, the cooling mod typically consists of removing a freeze plug from the rear of the engine on each head, typically the freeze plug that is facing upward on the same plane as the intake manifold gaskets, but other options include the freeze plug on the rear of the head which is harder to access. Some sort of fitting is installed in the place of the freeze plugs and hoses connected to promote flow. These hoses may be connected to the heater core supply or ran forward to join the cross over tube.

There are dozens of different ways the cooling mod is set up and there are a couple factors of design you should consider. Some cooling mods install fittings in each head and simply connect them together and call it good, while simple this design (IMO) does not flow as much around the backside as desired, but does not mess with the factory heater core supply or the COT/radiator hose. One popular production design has the two fittings connect to each other and a T that flow the coolant forward to a fitting added to the upper radiator hose near the COT this design is more noticeable from the front view of the engine but has the desired flow for even cooling. The most popular setup for Marauders is two fittings with a T that flows to the heater core supply, for a simple install on stock marauders, a 2nd T is added to the heater core supply hose and the stock hose is maintained, alternatively - this is popular when the COT is being modified already, is to delete the heater supply nipple from the COT and use the cooling mod fittings and hoses to supply the heater core alone, which should flow better.

The production designs are expensive, have clearance issues with different intake manifolds, but have better sealing with O-rings, most will be catered to mustang applications which will only include a fitting for the drivers side but several offer an option for Marauders that include fittings for both heads. Most of these are nice if they clear your intake manifold, the factory Marauder intake has allot of clearance problems but the intake can be trimmed down to make it fit most fittings, the eaton swap cobra lower is a little better, but cannot be trimmed as much as the marauder intake.

The less-than production home made freeze-plug style fittings are inexpensive and popular, but can be more intimidating to install and have had more issues with leaks that production options.

Another setup that I am currently using is the factory 03-04 cobra passenger side fitting. The fitting fits perfectly into the passenger side head and is easily modified to fit the drivers side head by drilling a mounting hole into the bracket and slightly bending the tube to clear the head. The fittings are o-ring sealed but install on the rear of the head instead of the top of the head which make install much more difficult in-car(although possible on a marauder, on a mustang however engine/trans removal would be required) and the fittings are somewhat difficult to find but were still available as motorcraft service parts last year.