3800 Using Coolant

[Matthew Jeschke]

My daily driver is a 2006 Buick Lucerne. It has nearly 190,000 miles. I've had to do very little to maintain the vehicle (list below of coolant maintenance). It seems to be using coolant and I cannot figure out how. Occassionally there will be a puddle under passenger side of engine compartment. I suspected water pump is weeping / going out. However, it's dry to touch.

Maintenance:

- New metal bypass elbows to replace plastic ones. Those had broken previous. Dry to touch now as well.
- New upper and lower radiator hoses. Dry to touch at water pump, engine, and radiator.
- Original radiator, no signs of leak on core support, holds pressure as well.

Symptoms:

- Occasional puddle of water under on driver side of engine bay.
- Fill up radiator and a couple weeks later will be down about a gallon
- No signs of water in oil.
- No smoke from exhaust.
- No signs of water / coolant leak under hood or on accessories. All dry to touch.

I hate to change the water pump if it is something else. I always like to get a good idea of what problem is before doing parts darts but seriously am completely baffled.

 

[Fless]

Rule out a head gasket by using something like in the link below. I think some auto parts places might "rent" them.

Combustion Leak Detector

Amazing deals on this Combustion Leak Detector at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

When the engine warms up, the coolant that leaks out (if there is any) can dry quickly on a hot engine and with air blowing by. Look for dry fluid traces everywhere underneath.

 

[exp500]

Put 2 Bars Leaks tabs or Gm tabs in radiator, then Think about how you want to test entire system.
Lastly a failing pressure cap can dump alot of coolant at engine shutdown. Good Luck!

 

[Matthew Jeschke]

Rule out a head gasket by using something like in the link below. I think some auto parts places might "rent" them.

Combustion Leak Detector

Amazing deals on this Combustion Leak Detector at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

When the engine warms up, the coolant that leaks out (if there is any) can dry quickly on a hot engine and with air blowing by. Look for dry fluid traces everywhere underneath.

Will do, there is crusty oily mess on accessories. Maybe that is my fluid.

Put 2 Bars Leaks tabs or Gm tabs in radiator, then Think about how you want to test entire system.
Lastly a failing pressure cap can dump alot of coolant at engine shutdown. Good Luck!

I wondered about that. My cap area is clean as a whistle though.

Mibd blow. I topped off last night. Opened back up cap, empty again. No fluid on floor though.

 

[Doubeleive]

My daily driver is a 2006 Buick Lucerne. It has nearly 190,000 miles. I've had to do very little to maintain the vehicle (list below of coolant maintenance). It seems to be using coolant and I cannot figure out how. Occassionally there will be a puddle under passenger side of engine compartment. I suspected water pump is weeping / going out. However, it's dry to touch.

Maintenance:

- New metal bypass elbows to replace plastic ones. Those had broken previous. Dry to touch now as well.
- New upper and lower radiator hoses. Dry to touch at water pump, engine, and radiator.
- Original radiator, no signs of leak on core support, holds pressure as well.

Symptoms:

- Occasional puddle of water under on driver side of engine bay.
- Fill up radiator and a couple weeks later will be down about a gallon
- No signs of water in oil.
- No smoke from exhaust.
- No signs of water / coolant leak under hood or on accessories. All dry to touch.

I hate to change the water pump if it is something else. I always like to get a good idea of what problem is before doing parts darts but seriously am completely baffled.

the best way to find the source is to put some CLEAN DRY cardboard under the engine area when you park it and leave it sitting overnight then in the morning look under the vehicle, find the wet spot on the cardboard and look directly up from there with a flashlight. if you are loosing a gallon every 2 weeks it should have some leak overnight.

 

[Matthew Jeschke]

Awesome thanks @Doubeleive I just pulled the t-stat (hate guessing if it's open or closed), topped the radiator off, made sure all the air was out of the system, then added to the revivor so I can tell if it sucked any in. Then set a really big clean piece of cardboard underneath that spans the entire hood compartment.

Studying cylinder leak down testing. I SURE hope it's something else. Quick gripe, I've had several of these 6 cylinder GM motors they are really AWESOME little motors except for ALL of them had pesky coolant issues like this.

 

[Jimmyy]

I know the early version of the 3.8 had issues with the upper and lower intakes leaking coolant.

 

[Doubeleive]

Awesome thanks @Doubeleive I just pulled the t-stat (hate guessing if it's open or closed), topped the radiator off, made sure all the air was out of the system, then added to the revivor so I can tell if it sucked any in. Then set a really big clean piece of cardboard underneath that spans the entire hood compartment.

Studying cylinder leak down testing. I SURE hope it's something else. Quick gripe, I've had several of these 6 cylinder GM motors they are really AWESOME little motors except for ALL of them had pesky coolant issues like this.

If you didn't take it out for a good run after that and heated it up to normal temp, then you may not get any results on your cardboard.
the theory behind it is some times these leaks can happen as it looses pressure over a extended period of time or from going from expanded (hot) to (cold) overnight thereby being able to dribble out of a un-expanded place as it shrinks back to normal. a gallon over 2 weeks is a slow leak but is enough that you should be able to spot it fairly quickly.

 

[Doubeleive]

also if it was going in the engine you should see a fairly good amount of slime under the oil filler cap even if was just burning it off. you would maybe also notice some sweet smell out of the exhaust

 

[Matthew Jeschke]

@Doubeleive your a godsend. I have enough experience here to be dangerous. I have smelt the exhaust, there is no odd smell, I also let idle in my garage for about 30 minutes and there was no water spot at end of exhaust. Oil looks like new, no slim on filler cap.

I'm so nervous about hydro locking though that I turned by hand after I filled it up last and crank turns w/o any issue at all.

I also drove to work just now. Was about 30 minutes of driving. Came back and put carboard back under engine bay.

Hopefully I can spot the pesky leak this time I've rebuilt a couple cooling systems for SBC and NEVER was this tricky. These little v6 motors are a bear with all the funky bypass elbows, I think coolant runs through intake, etc etc etc.