Overheating CJ7, the story so far

Friday, April 30 On trip to Irvine, it became apparent to me that my Jeep engine was overheating too much to ignore.

My temperature gauge has been dead for years, because of a failed voltage regulator in the fuel gauge that supplies both of them.

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Tuesday, May 4. Whereas I already had a spare thermostat ready to go, that became the first thing to attack. Before starting, checked the new thermostat in a pot of boiling water on the stove; it opens as expected. Pulled old thermostat, put in new one. Jeep still overheats. Old thermostat in pot on stove acts just like the new one.

Wednesday, May 5. Went to Pep Boys, bought a bunch of stuff. A nice mechanical water temp gauge. Prestone flush kit, consisting of tee fitting that goes in the heater hose for hooking up to garden hose, and a cheesy tube to divert the overflow a couple of inches away in a chosen direction. Bottle of flush chemical, label says it has sodium citrate in it. Bottle of water pump lubricant and three bottles of antifreeze. Cheesy Prestone hydrometer.

Installed the temp gauge in a fitting in the water passages in the intake manifold that, for some odd reason, I believed was where it was supposed to go. Readings very squirrely.

Modified the Prestone overflow tube by adding a hose fitting, so with a second garden hose I can route the overflow someplace inoffensive instead of dumping it on my shoes.

Thursday, May 6. Figured out that I had hooked up the new gauge wrong. The fitting on the manifold is the wrong place. The right place to connect it is on the block like God intended it. The gauge sensor is to big to fit there. Too bad, and it was such a great fit in the wrong place. Out it comes, and again I have no temperature gauge.

Installed Prestone flush kit. Prestone says to put the tee in the upper heater hose, where it comes out of the top of the engine. Problem is, my heater hose connects on the radiator side of the thermostat, while they assume it connects on the engine side. If I connect it on top, I will be flushing nothing but the top radiator tank. I connect it in the bottom heater hose. That way, the water at least has to go through either the heater core or the radiator core to get out.

Drained the radiator. Contents looking like swamp water, more brown than green. Hydrometer says there's not much antifreeze in it.

Flushed with water for a while.

Closed it up, added the flush chemical. Drove around the block until hot, then let it sit until cool. Drained.

Flushed with water again. Discovered that by squeezing the heater hose shut with vice grip pliers I could make sure the water went both ways, heater and radiator. Good. Unfortunately, as the thermostat was closed, I suspect not much flushing happened in the block water passages. I guess a fair amount of rust and/or sludge has come out. but I don't know what to compare against. Water coming out is clear.

Filled with good antifreeze and water pump lubricant. The passenger compartment heater, which has been almost useless for years, is now putting out heat, so at least I did that much good. Jeep still overheats.

(H) relates the story of a vehicle having the same sort of problem, cured by replacing an old tired radiator cap with one that hold the proper pressure. (H) and I make a late night shopping run to Pep Boys for a radiator cap and the Despot for some water fittings.

Friday, May 7. Hooked up pressure gauge to the Prestone flush port. On a test drive, old radiator cap blows off at 10 PSI. Installed new radiator cap. New radiator cap blows off at 16 PSI, matching spec. Jeep still overheats.

(H) finally talks me in to doing the compression check, to see if I have a blown head gasket. Cyl PSI PSI (each cylinder checked twice.) 1 158 158 2 173 173 3 158 160 4 165 163 5 163 163 6 150 156

We concluded no blown head gasket.

Talked to (D). He believes I need more flushing of the block water passages. And what else is there to consider? That and the water pump. So, I thing the water pump has to come off for inspection at least, and if it's off then maybe it is a dumb idea to not put a new one on even if it looks good. When it is off, that would be the time to flush the block. I don't know yet what kind of rig up I can use to flush the block.

Reply to
David Harmon
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Sounds like everything is in order. Normally if your flush cleans out the heater dcore, the rest of the system will be clean as well. The heater core is the most prone to clogging of any of the parts in your cooling system. If you have a clutch controlled fan, I would replace that. These have a life expectency and your CJ is at least 18 years old. It seems to be a common problem with Jeeps from what I've read on this newsgroup.

Chris

Reply to
c

what shape is the radiator in????

Reply to
Carlo

Reply to
Jerry McG

Reply to
L.W.(ßill)

On top of what others have posted, you may want to disconnect the lines to the heater core and flush in both directions. Don't let that crap from the heater core into your engine, radiator, etc...

I did this when I pulled my engine, and, even though I had flushed the cooling system recently, I was surprised at the amount of crap that came out.

Reply to
Michael White

Where does this crap come from? water in the system that's rusting parts? Or oil seeping in to the coolant?

Reply to
SB

SB did pass the time by typing:

not usually oil, that's a blown head gasket. It comes from having a poor PH balance in the coolant or excess minerals in the water used to fill the system. Long term it comes from corrosion of the sacrificial anode then the radiator and block.

Another source is that leak-stop stuff. Oh, it works in a pinch (on small leaks/seeps) but I've seen radiators with at least a pint of the stuff settled in the bottom.

If your in an area with high mineral content or acidic water you would be better off using the 50/50 mix sold in stores or using distilled water for filling the radiator.

Reply to
DougW

Ok....

To start, the drain for flushing the block is a square plug under the rear exhaust manifold on the side of the block.

Having the temp gauge in the intake manifold is a valid place for it. Air bubbles from a blown head gasket or trapped air 'will' affect the gauge readings.

Do you have a clutch on the fan? If so, it may be bad. To test heat up the engine and have someone shut it down while you watch the fan. A hot fan will stop spinning immediately. if it keeps on free wheeling, it's dead. No need to look any more, you have found it.

If the fan clutch is good, then how is the rad itself? What do the cores look like when you look inside. If they are all gummed up with deposits, it needs a serious clean or 'rod' job where they physically scrape the crap out.

Do you have coolant flow? Open up the rad cap and heat it up with the cap off to see if the pump is pumping.

This also allows you to check for a bad head gasket. A bad head gasket will foam up the coolant. It will look like someone put dish soap in it like mine shown here:

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(your readings 'do' indicate a blown head gasket at # 6 to me by the way)

That's all I can think of right now, good luck.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

David Harm>

Reply to
Mike Romain

Anyone use purified water? or wahtever you call it? DISTILLED! Brain freeze for a second there!

We use de-ionized water in the lab at work for cleaning stuff....which is great...but was told that it'll actually leach minerals out of things...like your hands...

Reply to
SB

SB did pass the time by typing:

Truly pure H2O (Molar) is one hell of a solvent and actually dangerous to drink for exactly that reason. Bottled distilled water isn't that pure, it just has most of the minerals removed. I use it all the time for both the battery and radiator.

Here is what my radiator (and fluid) looked like at 112,000 miles. Last drain was back at 50,000 miles.

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Clean, green, and within spec so I reused it. (less the pint or so that spilled all over me getting the radiator out) :)

Reply to
DougW

Reply to
L.W.(ßill)

L.W. (ßill) Hughes III did pass the time by typing:

Basically Molar == 100% pure or undiluted/uncontaminated. Heavy water is a different chemical than basic water.

Water = H2O (Two Hydrogen atoms and one Oxygen atom) Heavy Water = D2O (Two Deuterium atoms and one Oxygen atom)

Just to make things more funner.

Deuterium is a form of Hydrogen that sports one extra neutron FWIW, add another neutron to Deuterium and you get Tritium. All of which are present in your basic sea water but in very limited quantity compared to H2O.

It's called Heavy Water because it is. :) Of course you found that out anyway. Those pesky little neutrons add up.

Reply to
DougW

Reply to
L.W.(ßill)

Tritium was quite commonly used for your glow-in-the-dark dials back in the day!

We use a small amount of it at work.

Reply to
SB
3000 imperial gallons of normal water = 30,000 lb. your gallon is less (3.8 instead of 4.55 litres), so that would be about 25,000lb Deuterium has a molecular weight of 20 compared to H20s 18, which would make it about 28,000 lb ; about 2/3rds of the weight of that 5,000 gallon tank when full or H20.
Reply to
Dave Milne

Reply to
L.W.(ßill)

I never understood why the US went a different way on gallons -

1 imperial gallon of water weighs 10lb, 1 litre of water weighs 1 kg. 1 us gallon is 8 1/3rd lb

still, that must have been quite a trip, Bill !

Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ

Reply to
Dave Milne

Reply to
L.W.(ßill)

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