hey guys....I have a 97 4x4. Has the og 4.3 with only 147k on the dash. I'm having a hell of a time figuring out a coolant issue with it though. this is going to be somewhat a longer post than typical...I wanted to add as much info on what I have already done so far to help you guys better help me out on this issue so for that I do apologize...


ok so here it goes.......roughly 3 weeks ago while driving I noticed my temp gauge went almost into the red...as I was about to pull over it dropped back to normal. it stayed there for a few min then climbed back up to over heating and once again went back down to normal running temp. first though is thermostat went bad as I've had this issue in the past.....however upon checking the fluids I noticed my coolant was empty so I took it as the system was empty and that's why it went into over heating. after filling the coolant system back up I did a quick once over and seen no leaks. about a week to week n half later it did it again and once more there wasn't any coolant. I figured maybe I didn't get all the air out of the system and caused it to blow back out the overflow tube while driving so Sunday I did a complete system flush on it. after bleeding out all the air and topping off the coolant I waited for the system to pressurize. once it pressurized I went over every hose best I could and connection and could not locate any leaks period so I called it good. I checked the levels on Tuesday and they were pretty much were I topped them off at however this morning something told me to check it and when I did there was no coolant yet again. it literally took 2 liters of coolant to fill back up to where it should be. there is zero smoke out the exhaust so its not burning through the piston walls, there's no coolant in the tranny fluid or the oil as well. water pump leaks no coolant from either the pulley or the weeping hole. I literally drove for 40 min parked in a parking spot left it run sitting there for another 20min and no sign of anything dripping off the vehicle or any sign of a leak. I literally am at a loss at to what the issue may be and where the hell the coolant is going and at the rate it appears to be "disappearing" I would think a significant leak would show itself or something would be standing out? any help you guys can give will be a big help! oh and I also boiled the thermostat and it opens like it should so its good too.

 

If its not leaking out onto the ground, then its leaking into the engine. If there is no coolant in the oil, I would be willing to bet it needs lower intake gaskets and its getting burnt. Intake gaskets are a very common failure on these.
You could try pulling the plugs and see how they look. sometimes when they burn coolant like that the spark plugs will have a buildup on them.

 

is there a way to check from outside the motor if the gaskets are bad? I've looked around both upper and lower intake and couldn't find any leaks around either of them. granite everything was still connected on top and was hard to see 100% all the way around it but from where I could visibly see there was no leaks to be seen. id rather not go through the trouble of replacing the gaskets if I don't have to lol. thanks for the help good sir.

 

I understand completely. Its not a fun job. I would say given everything you have checked so far you have narrowed it down to the intake gaskets or head gaskets.
A couple things to check first. pull your oil fill cap off and look at the underside. if there is any milky oil on it, its possible that the antifreeze is leaking into the crankcase.

I would suggest doing a pressure check on the coolant system and that might help you find the leak also. Some parts stores will rent these test kits. This may help you determine if its intake gaskets or head gaskets.

Also take a bright flashlight and look around the back of the block if you are able to. Sometimes these gaskets will leak out the back of the intake and down the transmission.

My personal opinion, as long as the engine was not overheated into the red, i would be willing to bet intake gaskets, especially if they have never been changed before.

My dads 1997 did exactly what yours is doing with the disappearing coolant and no external leaks until one day the oil looked like a milkshake and the engine started knocking. His wife was driving it at the time and didnt know anything had happened so she just kept driving until the engine was toast.

 

Thanks man preciate the help.....ill look into the intake tomorrow when I'm off work....last night I got under it when I got home from work and the bottom of the oil pan and the front portion of the tranny pan seems wet where the sides are dry. It appears to be just oil on both but I can't be certain cuz I could have sworn I got a hint of coolant mixed in with it. Here's couple pics I could get from under it last night. Ive been using only water since this started so I'm not wasting money on antifreez. Pics not the best but best I could do at 1am lol

 

Well ch3cked the plugs and they look fairly good tho from my experience in looking at plugs which I do admit isn't a whole lot...im still thinking it's leaking at from the back though.....maybe around one of the water jets or something.....i remember hearing somewhere that the 2 in the back get clogged fairly easy so I'm thinking that's where it's leaking from....

 

Hmm - ever looked under the carpet at the passenger side?

I had the heater element leak on me. Could also leak at the hoses going into the element and run down along the firewall on the passenger side, then drip to the floor.

Also the plug on the manifold where the hot water for the heating comes from can develop a leak. The water would evaporate on the manifold.

And then some more thoughts that come to mind.
Thermostat put on backwards. Sometimes even when put on the wrong way they open when you overheat your system as the thermostat at some point is getting enough heat.

Has the v-belt been replaced? Check for correct routing. On some versions depending on A/C compressor and accessories it is actually possible to route the belt the wrong way which makes the water pump run backwards.

Ever pulled the lower hose on the radiator? Sometimes sediments are settling there and it should not be too much of a hassle.

 

Heater core is good and not leaking on passenger side...i actually replaced it last spring...i would think it still be good but never know so I did check for all that initially. Lower hose was taken off when I did the flush. If anything was in there I didn't want it going through radiator. Thermostat is correctly placed and the belt hasn't been replaced recently. I've literally went through every hose and every connection and could not find even the slightest leak or sign of coolant....thats what's making it so difficult to locate what the issue is...aside from changing out the lower intake gasket ive checked everything i can think of and feel like i'm at a stale mate on problem.

 

Leak down testing?
The rate of pressure loss should give an indication of how fast it looses coolant. This will then give an idea of the size of the leak. Many gaskets and leaks behave quite differently under different pressures.

Next would be a boroscope of all the cylinders to have a look if one piston has been washed down. The sparks can be an indication but need not be so obvious as a piston crown.

 

Any progress on finding the leak?