Jeep Head

[glenn kangiser]

Nice truck, Don.  Too bad the Jeep is being such a bear.  I have had similar problems in the past and also got tired of looking for the cause....[ouch]

[CjAl]

don i have seen those high flow pumps cause problems at speed. they cause cavitation at higher rpms

[MountainDon]

The XJ is not overheating for me any more. 



It is now overheating for someone else.     Full disclosure was made so he knows the entire story and was willing to absorb the risk.

[glenn kangiser]

That fixes it....

[MountainDon]

Postmortem...

After talking with one of the area's better custom engine rebuilders I have a probable cause for the overheating.  We have hard water with a high pH. It should never be used to dilute concentrated antifreeze. I was told that after many years of using regular antifreeze like green Prestone, mixed with our water (50/50 mix) it is not uncommon to see vehicles begin to show overheating problems. A scale can build up on the inside of the cooling passages. This apparently happens with greater frequency with all iron blocks and heads. The hotter the engine runs the more the scale can deposit out of the coolant and stick to the iron. The higher thew pH the worse the problem. A 1/16" layer of build up can slow heat transfer by 40%.

The preventive solution is to use either the pre-diluted antifreeze that is available, or to buy distilled water to mix with the concentrate. The solution at this point is to pull the engine, diassemble the block, take that to a good rebuilder who has the equipment to descale the internal water passages and then reassemble. Or simply install a re-manufactured block. He said that trying to descale the engine with cooling system cleaners does not usually work.

I knew there were good reasons to not drink our tap water. So we'll continue to drink reverse osmosis filtered water and probably simply buy the 50/50 pre-diluted long life coolant such as what the new Toyota has in it.