overheating 258 HELP!

Put the fan shroud back on, the shroud will make a big difference at idle and low speed.

-Brian

My 84 did the same thing after a 3" body lift and removing the shroud... I had to modify the shroud to amke it fit after the body lift... but it now runs cool...

Dennis Gann

I have an 81 CJ7 258 too, no fan shroud.

If a 160 is the only way yo keep the temp down, I would guess you have a blown head gasket.

I would try heating it up with the rad cap off and watch for many tiny bubbles and smoke coming out the hole or a major explosion of fluid when the t-stat opens.

On some, once the thermostat has opened you can put your hand over the opening and feel the puffs of compression.

Mike

brad smith wrote:

You have to be sure that you have the right waterpump.

There is a version for the Vbelt and another version for the serpentine belt. They spin backwards from each other. If yo have a serpentine belt conversion, but use the vbelt water pump, or vice versa, the impeller on the pump will be reversed and the coolant will not flow very well.

You could also have a stuck tstat.

My '81 258 (4.2L) has no shroud either. I also have no fan clutch, which presents its own issues, but overheating isn't any of them.

If he had a bad head gasket though, wouldn't he have oil and coolant mixed in either the crankcase or the radiator, or both?

Not necessarily.

I had exhaust chugging into my rad when it got hot and never really noticed it losing fluid until it got really hot and burped out.

I had millions of tiny bubbles in the fluid, it looked like dish soap and foamed over the top when heated up with the cap off.

I think the hole was small enough to need firing stroke pressure to pass gas through.

I have seen this on other vehicles too.

I would be checking on the pump too like you say, but he mentions he has already changed it.

Guess we should ask if he changed it before the trouble or after eh?

Mike

CRWLR wrote:

Yeah, that's true. It is always good to understand if the problems began before or after the last repair project.

How is your engine oil level and pressure guage reading?

If your engine has high mileage, a high flow oil pump could be in order.

For my 258ci powered CJ-7 (4.0 head, Clifford intake, dual outlet header; Motorcraft 390cfm carb) I use a PermaCool engine oil cooler with over-sized oil filter, AMC V8 3 core radiator, 180 degree thermostat, FlowKooler high flow water pump, high flow oil pump, and a FlexiLite dual electric fan (because of a 1" body lift). I have no overheating problems with over 272K miles on the block without a rebore.

As for a 4.0 head, it would be fun to look into HESCO's new aluminum 4.0 head. They will soon offer a standard head, ported, and fully ported version.

brad smith wrote: