Hopefully I didn't screw anything up too bad. '96 ZJ Laredo 4.0, mostly stock.

Found I had a coolant leak before leaving for work. Being late wasn't an option, so I did the best I could and put some reverse osmosis water in. Ended up getting down to 3 degrees while I was working.

There weren't any good options at this location for addressing a frozen radiator or to borrow a car for the few days it would take to do so, so I decided to risk driving it. I know this is not very smart (to say the least) but I don't think I had any other decent choices. Gonna start keeping some antifreeze in my garage now though.

Started up and ran just fine for about 10 miles until there was a bit of a rattling sound from somewhere under the hood, plus a loss of power, and both high idle in neutral sometimes and tending toward stalling at idle in neutral at other times. A little experimentation before getting to a place I could park discovered that the rattling went away while in neutral, and got much more intense as I applied throttle while in gear.

I let it cool down for a while then drive it the rest of the way home. Everything seems fine, but I'm curious what that rattle may have been, and what other damage I might want to look for?

I also can't find that leak anywhere... I've heard bad things about leak sealers, but if I can't figure out where the leak it I might have to resort to one.

Thanks for any input!

*edit* added engine size

 

Primary suspect for mystery water loss on the 4.0 is the water pump - the bearings wear and water leaks out, sometimes difficult to spot as water loss can be erratic.

 

I also suspect the water pump because of that rattling noise you mention. Now, things are not too bad, as the replacement one would be $20-$40, depends on the brand and setup. I'll give you the link to consider the options If you want my opinion, I'd recommend picking the pump by ACDelco, as it is exactly the same, as the OE one.

 

New parts will be here Monday. Went ahead and got an OEM radiator, pump with a metal impeller, high flow thermostat, zinc anode drain plug, and a lever vented cap for <$150.

In the meantime, I found that if I drain the radiator when the car is sitting and fill it before driving, the leaking water will freezer on the radiator and seal the hole almost immediately, although once it is off with a warning engine for a while, the ice melts.

What could go wrong?

 

Remember there will still be water in the block that will freeze and split the side out!

 

Thanks for a heads up! I come from a warmer part of the world that rarely, if ever freezes. Had no idea that ice forming could crack an engine block. Decided to just run it for a few minutes every few hours instead.

Seems to be good so far! Only a day and a half more of this...

 

Ice can crack a block but it doesn't happen that often.

 

Yeah, BUT! The block on the 4.0 is long and smooth on the sides and I've seen the whole side of them cracked out! There is a drain plug for the block on the side just above the oil pan near the middle between 3&4. There might be one on each side, IDK.

My grandfather told me a story about the time he filled his model T cooling system with kerosene so it wouldn't freeze! I wouldn't recommend it because of the fire hazard. He said back then, you had to use alcohol with the water to prevent freezing, then drain it while it was still warm because the alcohol would evaporate when the engine got hot. There were no pressure cooling systems back then. He said when it got REALLY cold, he had to drain the oil and take out the spark plugs for the night, warm the oil on the stove and bake the spark plugs in the oven in the morning before he set out for his grocery deliveries. It seems easier to wake up the horses!

 

I'm okay losing a couple nights of sleep to help prevent that, even if it's a fairly remote possibility. I believe that drain plug is just on the exhaust side by the way.

I've had a few parts in the oven before, but I think my wife would take issue with boiling engine oil haha

 

That bring back in incident from my younger days! My buddy had his wife almost leave him because he used her best 2qt pot to boil his motorcycle chain in! THe idea was to get heavy gearoil into the pins and rollers to help lube it for going thru streams. He had to buy her a new Revereware 2qt stainless pot! D'oh!

 

Lol... We used to "season" roller bearing assemblies by boiling in lube and letting them cool down to draw lube in as it cooled. Another one of those "traditionally correct" things to do that made absolutely no difference at all.

 

Yup.

My wife threw a fit when I helped my buddy find a pinhole leak in his jonboat by floating it in my swimming pool!

 

Ive done that with tires that have slow air leaks, lol