Coolant Disappearing

[sawmkw]

I noticed yesterday that the heater went cold and sure enough, there was no coolant in the expansion tank. I topped it off and then noticed the temp going up then down and when I checked it again, it needed filled again. All in all, I ended up adding 2 gallons. When I used to check it regularly, it never used any coolant but then my wife has been driving it and I have been negligent in checking it.

During the process of adding these 2 gallons, I checked for leaks...none. Also, it seems to be be running okay, although maybe a little rough which leads me to suspect head gasket. Other than that, what could cause coolant to disappear???

I've got 238K on her without any major engine work.

 

[Sepiroth]

You're going to have to have a coolant pressure test done when the engine is cold and hot. That will most determine where your coolant is going.

We can sit here all day and you could be checking this or checking that and still come up empty.

 

[sawmkw]

Coolant Found!

Seems it has been draining into the oil pan. I see it on the dip stick and it's draining in while sitting. Still sound like a head gasket? It was actually running fine with no engine lights although idling a little rough.

 

[Ojustracing]

So if its draining into the oil pan. Whats the oil look like? If you lost 2 gallons of coolant into the oil. Really bad chocolate milk shake? Way overfilled and this nasty looking glop too. I have hundreds of cars come through my door here at work with this issue over the yrs. I going to assume that by the amount of miles you have listed its not a 07+ tahoe and thats its a 96-99 one. If I had to make an internet guess it would be the intake manifold gasket is no good.

John

 

[sawmkw]

So if its draining into the oil pan. Whats the oil look like? If you lost 2 gallons of coolant into the oil. Really bad chocolate milk shake? Way overfilled and this nasty looking glop too. I have hundreds of cars come through my door here at work with this issue over the yrs. I going to assume that by the amount of miles you have listed its not a 07+ tahoe and thats its a 96-99 one. If I had to make an internet guess it would be the intake manifold gasket is no good.

John

It is a 1996 which has been taken care of pretty well. Oil has been changed every 3500-4000 miles. The oil now looks like a bad chocolate milk shake and is way overfilled according to the dip stick. What is the best way to check whether this is an intake manifold or head gasket?

 

[Ojustracing]

My take on this, if you had a headgasket leaking that bad there would be a whole bunch of other issues. These intake gaskets do have issues and can/will dump large quanities of coolant into the oil. As for verfying the leak, that might be kinda. But if it were at my shop I would try and pressure test to see if I can hear the air escaping or many time when the gaskets are this bad they will also be leaking externally also. You have to look where the intake manifold and the heads come together to see if there is any leakage in those area. But because you have so many miles on the truck and the amounts of coolant in engine and a unkown length of time driven with coolant for oil(This is really bad). A intake gasket might be wasted money, unless you do your own work.

John

 

[73shark]

My experience w/ SBC and water in the oil has been where the crossover between the heads is where the leak occurred on two of them and a microscopic crack in the block between the #5 & #7 lifters on the other one. The intake leaks were much worse than the crack.

 

[sawmkw]

But because you have so many miles on the truck and the amounts of coolant in engine and a unkown length of time driven with coolant for oil(This is really bad). A intake gasket might be wasted money, unless you do your own work.

John

My best guess is that the coolant was in the oil for 2-3 days although it did get a fair number of miles on it (50 or so) during that time. The oil was chocolate in color but no globs as if there had been water in the oil for an extended period of time. From what I have been able to find out, coolant in the oil could damage the bearings but would it do that damage in this amount of time? I'll probably need to do the work myself but wonder how deep I should dig.

 

[rockymt21]

I noticed yesterday that the heater went cold and sure enough, there was no coolant in the expansion tank. I topped it off and then noticed the temp going up then down and when I checked it again, it needed filled again. All in all, I ended up adding 2 gallons. When I used to check it regularly, it never used any coolant but then my wife has been driving it and I have been negligent in checking it.

During the process of adding these 2 gallons, I checked for leaks...none. Also, it seems to be be running okay, although maybe a little rough which leads me to suspect head gasket. Other than that, what could cause coolant to disappear???

I've got 238K on her without any major engine work.

I just had this same problem, turned out to be the water pump.

 

[sawmkw]

I just had this same problem, turned out to be the water pump.

A faulty water pump can dump coolant into the oil pan???

 

[Ojustracing]

My best guess is that the coolant was in the oil for 2-3 days although it did get a fair number of miles on it (50 or so) during that time. The oil was chocolate in color but no globs as if there had been water in the oil for an extended period of time. From what I have been able to find out, coolant in the oil could damage the bearings but would it do that damage in this amount of time? I'll probably need to do the work myself but wonder how deep I should dig.

I can 100% guarantee to you that these gaskets leak some coolant into the motor before you can see it. They do not just on one day fail and dump the coolant into the oil. So it has had some coolant in the oil for a considerable length of time.

Your issue is with the amount miles on the motor. If you bring it too a shop its going to be Aprox $500-$600 to fix. That an expensive price to find out that 1 or 2 month later the motor has bearing issues. That money could go towards another motor. If it was a my shop we would be having the same conversation. Im just trying to be realistic. I have had a bunch of v-6 gm with the same issue and there motor have been okay, but again not ones with this many miles.

I hope this helps you. Any questions feel free to ask

John

 

[Ojustracing]

A faulty water pump can dump coolant into the oil pan???

NOPE!!!!!!!!!!!!!

It can cause you to loose 2 gal on anti-freeze but but not into the oil pan.

John

 

[rockymt21]

Yeah my bad, didn't read the part about coolant being in the oil pan.

 

[Ojustracing]

Got Scott all fixed up. Intake manifold gasket was no good.

John

 

[sawmkw]

I recognize that this forum is not to be used for advertising or to drum up business but it does brings together people with a vast amount of knowledge and helps people like me determine whether they have the skills to do a repair. After reading the posts and recognizing that OJustRacing (John) had accurately diagnosed my symptoms right down to the oil looking like a chocolate milkshake, I contacted him off forum for some additional advice. I was recognizing that (1) this was a bit larger job than I was ready to tackle and (2) I did not have the time to do it. My Tahoe is in pretty decent shape, been well taken care of and has never been in an accident. But as a 96 with almost a quarter million miles, I wanted some help in making a decision on whether to make the investment and repair her or say goodbye. I learned that his shop was only a couple hours away and was able to talk John into taking a look. Living in Middletown CT, I have had dismal experiences with both the area dealers and the independent shops that claim to take “personal auto” care. It was worth the cost of the flatbed ride to get an honest opinion.

Long story short, I drove her home from Albany today with new manifold gaskets, water pump, thermostat, hoses, PVC valve, fittings, serpentine belt, oil pressure sender, coolant and a couple of oil changes. The cost was more than fair, but far more importantly I felt confident that my Tahoe was being repaired by someone who actually took personal pride in their work cared about the job. She was a bit stiff for a while but it was minus zero during the night and barely in the single digits when she fired right up.

I’m elated and thankful that this forum exists for the do-it-yourselfers (me often times) and those that need to find experience that they can trust. I’ll see John again and, Thanks All!

 

[Ojustracing]

Scott thanks for the kind words.

John

 

[gus06608]

adding coolant

every couple of day i have to add coolant ,i had it presser check ,doesnt over heat ,truck runs good ,heater in the truck works find ,and their no leaks .what can it be

 

[MO Viet Vet]

May be head gaskets. Start of slow coolant loss that will escalate. Start another thread so we all can stay organized on this.

 

[lesterl]

Check the oil level.....