overheating continues

Guys, I'm stymied on this one. Any and all suggestions appreciated.

1975 CJ5/258..approx 40,000 original miles. Few years back while in storage, I would take her out and temp gauge would read right in the middle of the green zone. Took her out of storage recently and have been doing a gradual 'commissioning' to get her back in shape. New brakes, electrical and gauge work, HEI distributor, new water pump, radiator, 190 thermostat, fan shroud.

My main problem continues to be overheating. After warming up she stays at the high end of the green zone, just a tad below the H. Today I took her to a shop where they ran a pressure test on the system. Checked out OK, so at least I don't have a blown headgasket. Also no telltale water in oil or white smoke on start-up. Whew !!

Mechanic shot temperature readings at lower and upper hoses and 40 degrees of difference.Radiator is doing its job. He thinks it is some sort of blockage in the engine itself. Very well could be since she has spent the bulk of the last ten years sitting up.

Now the question......short of a total engine removal and thorough cleaning of all passageways (read expensive!!) are there ANY options to try without tearing into the block.

 

Get one of those back flush kits and see if that will help.

 

I'd flush the junk out and see if that helps. 10 years is a long time for rust and scale to build up. Or you may have an air pocket in there that just hasn't worked itself out yet.

 

Sounds like it could be something not involving the cooling system... I'd try new spark plugs, and double check the timing. It may be running lean... check to make sure the carb is tight on the manifold, and the carb body is tight on the throttle plate. I'd also check to make sure that the intake and exhaust manifolds are tight.

 

try a mechanical temp gauge

 

fan blades on correctly...pulling air in not pushing air out?

 

My '74 sat for about 10 yrs too. I recently had problems with overheating also, but only under heavy load, steep climbs and such. I brought my rad in to have a mount resoldered and the rad shop found that more than half the tubes were blocked. I took the opportunity to get a new rad and replace the pump, thermostat, and cap. The hoses were done last year. There was a lot of crap in the rad and block after flushing.

Karl

 

Thanks for everyones input. The timing is spot on when I installed the HEI distributor and I put new plugs in at that time also. Also new three core radiator and new water pump. Fan blade installed properly and pulling air through the radiator towards the rear. Basically, EVERYTHING related to cooling has been replaced and it seems to be a water volume issue.

I've been doing some GOOGLE searches on overheating,and I believe the intake manifold is part of the coolant routing through the block.This could be the culprit.

My plan is first to remove the thermostat entirely (even though it is brand new, I guess some are defective) and see what that does to temperature. I expect it to act the same. I also will check tightness of manifold bolts, carb bolts and anything else I can get a wrench on!

Next is to use flush and backflush kit to try to remove blockage. Some websites have recommended distilled white vinegar and also CLR to loosen up rust/deposits. Not so sure about that stuff.

BTW...carburetor is Carter YF and seems fine. Could adjustments on the carburetor affect overheating? Maybe to a small degree, but I don't think it would be a major player. Also, heater core seems fine, but I might try bypassing it to see if that has any influence.

If none of these work........this weekend I'll try pulling the manifolds off and see what they look like. Really looking forward to that.....oh well....as long as they're off, guess its time for the manifold dressing...

It never ends, does it ?

Boy, I'll be glad to get this one solved !!

 

The real deal for block/radiator cleaner is oxalic acid. OA combines with rust and is very effective. It used to be sold in a 2-part silver can from DuPont with the cleaner in the top and the neutralizer in the bottom. I have not seen it at the local AutoZone ever; maybe it's too hazardous or polluting to be sold through retail channels now. I would expect that one of the active ingredients in CLR is OA.

 

Based on my personal experiences and the fact that you installed a new radiator, I have found that if it only heats up idling or under a lower rpm load where there is very little or no ram air across the radiator, i.e. hill climbing, the fan may not be pulling enough air across the radiator. Either due to the fan not turning fast enough, fan pitch or radiator shroud. I have also seen a stuck thermostat cause a low idle heat up. If the aforementioned does not remedy the problem then I would suspect plugged water jackets in the head(s) since it sat for 10 years.

If it only heats-up down the highway it may be a circulation problem since there is plenty of ram air across the radiator but the water is not entering the radiator fast enough. The fan and shroud are pretty much irrelavent at highway speeds. Again I would suspect thermostat or plugged water jackets, in that order.

I understand you replaced the thermostat but new doesn't necessarily equal good.

The thermostat is where I would start.

 

Well, looks like the problem is close to being solved. Yesterday afternoon I totally removed the thermostat and she ran cool as a cucumber. I had to pop a brewski after watching the temperature gauge remain in the 1/3 range. Also nice to see the coolant circulating through the radiator.

After waiting a while for it to cool off, I removed the thermostat housing and installed a 195 thermostat/gasket and topped off the coolant. Fired her up, gauge climbed to almost hot and no circulation in the radiator......so obviously a thermostat problem.

Think I'll try drilling a 1/8 " hole in the top of the thermostat and see if that helps. Seems to be a air pocket that forms that keeps the thermostat from opening at the proper temperature........

Feel kind'a stupid for doing all the other cooling upgrades and it looks like its a $5.00 thermostat problem that caused me all the grief. Well at least I know the cooling system is at a 100% and I think I could probably change out a thermostat in pitch dark with all the experience I've had over the past coupla weeks....thanks for everyone's suggestions !!

 

Doesn't the manual call for 180 thermostat? That should work better for you, I would think.