Rear Head Cooling System Kit

Cracked Block Article

If you have an engine 'At Risk' this is the only thing you can do that might keep it from eventually cracking.

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Rear Head Cooler Kit

FSD Master Kit

345.00 each includes Shipping (Canada shipping 20.00)

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The engine in my 98 blew luckily when it was under warranty. I know lots of guys that have had their engines replaced. I decided to start selling this kit because it's about the only thing you can do to possibly alleviate the problem. I installed it on my engine even though it's a new one. What it does is keep the temperature in the heads and top of the engine even. This should put less thermal stress on the block possibly keeping a truck that's 'on the edge' from actually cracking. It also should help prolong the life of your head gaskets. The rear cylinders always get hotter because they are farther from cooling air and the coolant in the heads doesn't flow through like it now does with the kit. The only 'visible' change to indicate that something is different is that the heater in the truck warms up faster. This kit works with both the turbo diesel and the N/A diesel engines.

The GM diesel in the Hummer has 2 water jacket outlets blocked off in the heads. Opening these up and allowing coolant to circulate through the heads will keep the heads, especially the rear sections cooler and less susceptible to stress and cracking. This is what the kit does. It is not a cure for any other cooling problems. It's simply an enhancement to the original cooling system.

Another benefit which is a byproduct of the enhanced flow is that the temperature of the heater rises much faster in cold weather providing heat to the passengers much sooner. This is a result of the coolant routing through the heads going directly to the heater hose.

The fact that the heater warms up faster is an indication that more heat then before is being picked up from the new installation. The truck will run at the same 195 - 200 like it always has. The kit will remove more heat from the hotter rear cylinders evening out the temperature differential in the engine, not change the cooling system temperature.

Rear Head Cooling KitThe kit consists of 3 Stainless steel braided hoses, 2 hose clamps, a custom 'T', 2 custom block off plate adapters and gaskets.

Use a large drain pan or a 5 gallon bucket and drain the coolant by opening the petcock on the bottom of the truck and the bleeder screws on the front crossover on the top. Pictures of this are in the change your antifreeze article. While the coolant is draining remove the inside 'doghouse' cover and rear engine cover to gain access to the rear of the engine.

Remove the turbo heat shield bolts. There are 4 - 10mm and 2 - 15mm heads. Note the location of spacer washers on the upper left 15mm bolt for re-installation.

Remove the oval block-off plates at the ends of both intake manifold runners on the cylinder heads.

Install the new plates with fittings on correct sides (labeled) making sure to properly remove the old gaskets to prevent leaks. I stuffed a towel in the water jacket to keep the old gasket scrapings out.

Note: This is a good time to tighten up all the bolts on the turbo and manifold and check for leaks. There are gaskets on the manifold and an o-ring on the turbo.

Replace the turbo gaskets and seals

Right plate Left Plate
Right Plate and the Left Plate

Install hoses labeled 'drivers side' and 'passenger side' routing hoses for minimal contact with other parts to reduce chaffing and burning which can lead to future leaks. If the hoses aren't labeled just dry install them to see what fits the best. The passenger side hose is a tight fit under the glow plug controller and actuator. The glow plug controller bracket may need minor flexing to ensure clearance. Be careful that you don't short the braided line on the 12v glow plug controller power lines. The 90 degree fittings can be rotated slightly if needed for better fit.

Make sure that the fittings are tight in the plate. I put the whole thing together and had a leak where the passenger fitting screws into the plate. I had to drain the antifreeze all over again and fix it. I was able to turn the fitting in the plate another whole turn. Use sealer on the threads. I used Locktite 518 gasket eliminator. Sometimes we supply the parts with white teflon sealer already on the threads.

Use the new gaskets supplied with sealer if desired. Be careful not to damage the Turbocharger actuator rod.

Remove the Intake tube from the air filter housing to the turbo inlet.

Tee the hoses together at the turbo inlet and install the third hose to the passenger side at the front of the valve cover.

At a suitable location cut the 5/8" heater hose from the crossover pipe and install the 5/8" x 4 Tee fitting with clamps supplied. You might want to use a new hose. You can use some grease to help the rubber hose slip on the fittings.

There's all kinds of things you can do while the engine cover is off.

Check both turbo inlet pipes for any signs of leakage or cracking. This has been a common problem on Hummers for years. If there are signs of leakage replace the pipe. You don't want engine fumes, heat and noise near the passenger space.

You might also want to replace your CDR valve and the thermostats while the coolant is already drained.

This is also a good time to replace or antisieze your glow plugs because they will be easy to get to.

Check for oil leaks around the turbo and intake manifold. There are gaskets on the manifold and an 'O' ring on the turbo. Replacing these is a real pain.

You might also get the engine casting number for future reference. I'm going to add insulation to the engine cover to help quiet the truck down.

Check that all hose connections are tight. Refill the cooling system following the manufacturers instructions and install the air intake tube.

Hold all the wires away from the rear of the engine so they don't get burned or melted. I used a piece of 2x4. Start the engine and while warming it up keep an eye on all the coolant connections. The diesels are hard to get warm while idling so you might want to take it for a drive. Just watch out for all the hanging wires. Check all connections for leaks and double check the fitting torque.

If everything is OK and there are no leaks reinstall the turbo heat shield, engine cover and doghouse.