The #4 Coolant Mod... ---------- Converted

[Frank]

#4 Coolant Mod

Undoubtedly one of the easiest coolant mods, this will directly inject cold coolant to the #4 cylinder. This is important since the head coolant flow leads to hot stagnation with high horsepower motors.

TrboVan used 1/4" pipe on the waterpump housing and the head. A straight hose barb on the waterpump side to clear the Alternator bracket and a 90 degree hose barb on the head side. These were connected with -4an hose. Make sure to use the appropraite drill bit size for 1/4" pipe thread.



(now need picture of the hose installed) (pics from Bryan Lugert)


BFnGA says that when drilling the holes into the head and water pump, start with a small drill bit and drill it incremently larger. He used a 3/8" NPT for his setup with a 7/16" drill bit.

(need to get pictures from BFnGA of his setup... )


Additional Notes:

Whilst drilling my hole for the mod as bryan did it, I just barely nicked the passage for the head bolt. I would add that removing the valve cover to make sure of where the bolt passes through would be a good idea.

I made this mistake with the head off of the car, so it has got to be an even more real possiblilty for those attempting to do it while the head is still on the car.

Keep up the good work,
-Brian W. Cordes

Frank

[rbryant]

I found something interesting in the junkyard today on the number 4 cooling mod!

VW apparently was more worried about this problem on their 1.8l engine than ChryCo was because they actually did a #4 cooling mod!

Their 1.8/2.0 head actually is layed out much like the 2.2 (the 1.8 and 2.0VW engines share the same block with the 1.7 but Chryco made their own 1.7l head rather than using VWs)

Here is the head showing the similarity in location of the water outlet:



The forward connection goes to the radiator and the side goes back to the water pump pressure side. Note that the thermostat is actually in the water pump's radiator return line.

The interesting thing is that it also has a freeze plug in the side but is tapped for two holes so you can put one of these on it:



The VW part number is: 026-121-145 in case it is hard to read. It is for a 3/4" line rather than 5/8 but that isn't a big deal. The common block water pump has a 3/4" inlet on it anyway so we are used to dealing with this and already know what to order or use when we have 5/8" hose with a 3/4" connection...





The oring means all we have to do is drill and tap two little holes in the side of our head for 10mm headed bolts. Or even some 1/4" bolts if you happen to have that tap handy!

The line then simply goes through the heater core and back to the water pump post thermostat (no thermostat control, no passing through the radiator, no collecting $200).

The bigger thing is that this shows that VW felt that the proper way to do the number four cooling mod was to simply return the water to the suction side of the pump. I have felt this all along and feel that we should plug the old heater core feed line and feed the heater core from a #4 mod. If it makes you feel better you can tee it with the #4 mod and feed the water to the heater core but either way the heater core normally takes water from the engine and returns it to the water pump without going through the thermostat or the radiator.

The one thing I haven't wrapped my head around is that VW actually sends a 3/4" line back from the pressure side of the water pump to the #3/#4 cooling outlet... I have to think about this a bit more but I believe it isn't a major difference... The coolant will not pass through the radiator when the stat is closed because the outlet of the rad will be plugged. that means the water will go through the engine both through 1-2-3 as normal and through the 3-4 outlet and back out the #4. Most of the flow should however go through the entire engine.

When it is open the pressure side line will force water to return directly through the radiator for a second pass along with the normal water from #3/#4 and some percentage of water will go directly from the #4 to the suction side of the water pump to circulate again. Hose sizes play a big part here and I haven't done the math or thought about the radiator as a restriction....

In my setup the water will go through the entire engine when the stat is closed but not the radiator. When the stat opens it will go mostly through the radiator but some percentage will go directly from the added #4 outlet to water pump and circulate again..

I believe the only difference is that more water flows accross the #4 with the pressure side connection to the #3/#4 in/outlet. But either way more flow gets out of the #4 even without it.

If you pick up one of these you will be amazed at how nicely it fits on the 2.2 8V head. It looks like it was made to be there and Chryco just forgot to drill and tap the holes for it....

-Rich