Still trying to figger out what's happening to my coolant

[Skunksmash]

87 tbi 350. My coolant is still going somewhere, but I have no idea where. Its not in the oil, its not on the ground. But every so often, I have to put a couple quarts in there. Also, you can't fill the overfill jug to the line. If you do, it will all be coughed up out the overfill lid. Weirdest thing I ever saw. Just takes a few days time.

It finally got a little cool here in TX so I decided I needed to turn on the heater. It didn't work, so first thing I did was check the coolant. It was low. Filled it up, heater worked again. So any idea what the heck could be going on here? Mysterious vanishing coolant. And a puking overfill jug. But only if you actually fill it up to the fill line. If you just leave I just leave it dry, I don't have that problem. But I'm wondering if maybe its a symptom.

[hobbz]

Is it coming out of the exhaust?

[crashz]

How do the plugs look? What does the exhaust smell like when cold and alos when hot? Any sweet smell? A few really clean plugs may indicate burning coolant.

If you fill the resevior and running the engine, can you see bubbles (be very carefull of splash back) in the resevior?

[tucsonjwt]

If no white smoke coming out of the exhaust (and a new Pope is not being elected) I would check for a leaking heater core - should smell like coolant from inside the truck, and may have coolant under the carpet. Heater cores are cheap and not too bad to replace.

[RastaRobb]

Any of those scenerios are possible, and bad. Bubbles, clean plugs or sweet exhaust pointing to a head gasket. Have you checked each cylinder compression?

[custom97]

Intake gasket

[GM-power]

Originally Posted by custom97

Intake gasket

X2.. but check your plugs to. If the heater core is leaking I thonk youd see and smell it by now. Probably leaking at the intake and gettin in the oil.

[willett]

I had a rad leak once that was pretty intermittent and it collected on the rad support and seldomy made it to the ground. You should toss a pressure tester on and use your ears.

[LynnJr]

A cracked head will do the same thing and the heads on these trucks are known for cracking.
I have cracked 3 heads so far and on mine it would swell the radiator hose enough that it would rub on the crank pulley until it finally let loose.

[Skunksmash]

Thanks for all the replies everyone, but fortunately, its not in the oil. No exhaust sweet smell, no smell inside the cab. No leak inside the cab. These reasons are why I'm confused.

Originally Posted by willett

I had a rad leak once that was pretty intermittent and it collected on the rad support and seldomy made it to the ground. You should toss a pressure tester on and use your ears.

Will do. Only thing I can come up with, its that its leaking so slowly, that its not ever getting a chance to hit the ground. It just evaporates first. Either cause it landed on something hot, or cause its just too small of a leak to ever really get to the ground. Yet over time, its still big enough to make the system lose a couple quarts. Last time I topped off the system, it lasted all winter. I never had to add more cause the heater stopped working. Took me till the next winter to notice it again.

[Sabaka454]

Pressure test it. Put dye tracer in it. Pick up a combustion leak tester.

[Boom]

If your getting pressure with the cap off like you describe it's likely a head gasket or cracked head. There are tests that can see if exhaust gasses are coming into the radiator.

[Corts60]

X2 on the pressure test. It is the only real way to find out the issue and eliminates guessing.

[SCOTI]

Originally Posted by custom97

Intake gasket

x2. I chased this similar situation in my dually. I lost the battle & seized the motor. Head gaskets were good & no cracks in the heads upon pre-rebuild inspection. Attempts to resolve the issue before the motors abrupt seizure included replacing the water pump, hoses (radiator & heater), pressure checking the radiator, new overflow container, & by-passing the TBI adapter tempering loop. On mine, I could go for weeks (short drive to work) w/o issue. It was the occassional highway jaunt that alerted me to the issue.

Never saw signs of water entering the crankcase until the fatality. When I changed the oil (before pulling the motor out), I drained off about a gallon of water before seeing any sign of petroleum.

[tucsonjwt]

You can have a slow leak in the heater core and not notice the smell inside the cab. Lifting up the carpet and pad near the firewall on the passenger side is an easy and quick check.

I had a leak at the nipple on the intake manifold. The coolant would evaporate when the manifold got hot. I finally discovered a little puddle of coolant and evidence that coolant was there on the intake (white residue where the puddle of coolant was) and replaced the nipple and hoses. I had a big block, so I had to get specially shaped nipples to make it work, but small block nipples are available anywhere. I used teflon tape to install the new nipples. This is a problem I had with my other small block Chevys but it is a known weakness on big blocks (at least the two I have owned.)

If you remove the nipples do it carefully. All of the ones I removed were rusted and the threads came out in pieces. Use lots of PB Blaster and go slow and easy. It is surprising how much rust is in an engine's cooling system.

[Skunksmash]

Thanks again for all the help everyone. It would seem to me, that if indeed it was a cracked head or a head gasket problem, that the problem would be visible, on the dipstick. There is none. Just oil. Is it possible that the crack or fault in the head gasket, is on the ouside of the head, and thus no water would be able to get into the oil? Could the fault lie in a particular spot on the head or gasket, that would allow water to leak, but not be able to get into the oil? I'll do the pressure test when the weather clears up. Right now there is ice everywhere.

I'll rent a pressure tester from Oreilly's. And check all those spots yall recommended.

[Sabaka454]

Originally Posted by Skunksmash

Thanks again for all the help everyone. It would seem to me, that if indeed it was a cracked head or a head gasket problem, that the problem would be visible, on the dipstick.

Nope, only if it's leaking into the crankcase. It can enter the combustion chamber without leaking inside the crankcase.

[LynnJr]

Sabaka454 is correct.
The heads on the 350's crack on the flat area of the combustion chamber and you don't see it in your oil.Eventually the crack gets big enough that the motor running pumps pressure into the radiator and your hoses will blow out or you will lose a radiator.
If you go to o'reilly's they sell a kit for checking for cracks.It looks like a turkey baster and a bottle of purple liquid.You warm up the truck and put some purple stuff in the baster then suck up some radiator fluid.If the radiator fluid makes the purple stuff turn a certain color its a intake gasket,head gasket or cracked head or block.

[motornut]

when I couldn't find a leak,would appear to sweat on the crossmember turns out bolts on left side of water pump a small leak

[Skunksmash]

Originally Posted by Sabaka454

Nope, only if it's leaking into the crankcase. It can enter the combustion chamber without leaking inside the crankcase.

But if it got in there, wouldn't it still eventually end up in the oil? Cause then it would get by the piston rings. Eventually. Or are you saying that it would go out the exhaust then? Cause I don't have the sweet smell

[donut]

It could go out the exhaust before you see it in the crankcase... for now.
The problem won't get any better.

[Axle]

How old is your water pump? A very slow seal leak in the water pump will drip slowly out the weep hole, and evaporate off the engine quickly. Take a mirror and take a look for staining around the weep hole.

Alex.

[Corts60]

The proper way to find the leak is to perform a leak down test of each cylinder. OTC makes a tool for this. From the symptoms I can gaurantee you have either a bad head gasket or cracked head. If it is a slow leak, the combustion temps will burn up the water before it has a chance to seep into the crankcase so that is why you don't see it in your oil.

The second you said water will cough out of the overflow can was a dead giveaway that combustion pressures are getting into the coolant.

[Chevy3+3]

Originally Posted by Skunksmash

Thanks again for all the help everyone. It would seem to me, that if indeed it was a cracked head or a head gasket problem, that the problem would be visible, on the dipstick. There is none. Just oil. Is it possible that the crack or fault in the head gasket, is on the ouside of the head, and thus no water would be able to get into the oil? Could the fault lie in a particular spot on the head or gasket, that would allow water to leak, but not be able to get into the oil? I'll do the pressure test when the weather clears up. Right now there is ice everywhere.

I'll rent a pressure tester from Oreilly's. And check all those spots yall recommended.

I owned an 87 tbi for years. It was high mileage truck. I had the same problem for a long time. I just kept adding coolant & water a couple of times a year. I couldn't ever find any leaks anywhere. It finally started getting worse after several years. The truck always ran great. When my transmission went out I was unbolting the bell housing bolts and noticed some moisture on the backside of the passenger side head. It was hard to see. Well I figured out it was my head gasket with a very small leak. So small that the coolant/water was evaporating before making it to the ground. So I decided since I had the extra money and the tranny was already unbolted.......i yanked the 170k factory motor and rebuilt the motor.

My buddy has a newer 2003 chevy. Had the same problem. Would get low on coolant only a couple of times a year. We could never find any leaks any where. This went on for 60k miles!!! Then one day he noticed a coolant drip under his truck. Took a little time to trace it but it was actually coming from the water pump gasket. The moisture was again so little it was drying on the block and never getting to the ground. It was tight a hard to see anyway.

I know how you feel. Its always irritating when you can't find a problem that you know exists

[piecesparts]

Most radiator shops have a test, that they can run to see if you have exhaust gases in your radiator. The chemical used will change with the introduction of hydrocarbons to it, so you cna see if you head gasket is leaking. I had it happen to me and that is when I gave up the original 305 in my truck and got into a 350. Now it is a 385 stroker engine, so watch out, once started, you will not stop.