Strange Coolant puddle....from where ?

Opinions please.....

99 Blzr, 168,709mi, 4.3LW, 4WD

I will describe my actions but noticed dexcool on the floor.... Normal condition on this car is no a single leak of any fluid from anywhere, anytime.....bone dry all the time...

So I am working in my garage and was rotating tires, grease front end this weekend...I do one side start the cold motor up back out and turn it around back in garage.

Rotate right side tires, grease right side fittings lower car restart engine which is still cold and pull out so I can work on my daughters car.

Look down and there is a 3" dia puddle of dexcool....I go out in the drive way and crawl under the car and notice that dexcool had dripped onto my exhaust cross over pipe...WTF... :crying:

After crawling around for 15 minutes I could not for the life of me find a hint of leakage i.e. head gaskets, intake manifold (at least that was visible).

It appeared to roll down the bell housing just behind the engine drop just in front of the tranny pan left side onto the cross over pipe.... :confused:

I dried the area with car cleaner ran the motor upto temperature saying if it's gonna leak let it leak so I can find it.......and you guessed it...not a drop, no leak, bone dry.....ran the car that afternoon about 140 mile round trip to a grad party came back parked on white cardboard in garage, jacked it up, nothing...bone dry WTF. :shakehead

Let the car sit over night figured as it heat soaked and cooled down, I'd see something.....nothing bone dry... :uhoh:

The puke tank level was exactly where I marked it...showing 0 loss.... :confused:

Checked the oil...as I am in the 1st rinse phase of AutoRX perfectly clear looking oil...no signs of coolant...WTF :headshake

Checked heater hoses, joints on firewall nothing...all tight, new, secure...other hoses, i.e. radiatior ...tight secure... :headshake

Frost plugs, dry, clean....motor block dry clean.... :headshake

Performance is good......idle is smooth, temp is good, nothing...it's like it never happened......


Can this be a fluke ??? Possible intake / head gasket that when hot does not leak ?? :confused:

What kind of leak would not leak under hot expansive pressure of 16PSI and temps of 198-F ???? Yet would leak a dribble under 70-F temp and little expansive pressure...i.e. thermostat would be closed....??? :confused:

Lastly...I know it was coolant by smell...definitely not tranny fluid checked all that out... :headshake

I have run the truck 5 times, upto temp with out a single drop on tranny area etc.... :confused:

Any other suggestions would be appreciated.....hate to rip apart stuff when it doesn't do it.......I am very confused... :banghead:

Turn on your heater and give it a try. I'm not positive but I think the Blazer uses a valve to cut off flow to the heater core when the heater is not in use. If it's the core or the hose leading to/from it you might have gotten just a short bit of coolant flow at initial start-up before the vacuum signal closed the valve. (Assuming that the valve is vacuum controlled like the one in my Camaro was)

Slightly off-topic: Ditch that Dex-Cool crap. I had to replace my wife's Blazer's Radiator, water pump, and most coolant lines because that garbage turned to sludge long before it's indicated time/mileage. The insidious thing is that the sludge/corrosion buildup nicely matches the color of healthy Dex-Cool so it's tough to spot.

Turn on your heater and give it a try. I'm not positive but I think the Blazer uses a valve to cut off flow to the heater core when the heater is not in use. If it's the core or the hose leading to/from it you might have gotten just a short bit of coolant flow at initial start-up before the vacuum signal closed the valve. (Assuming that the valve is vacuum controlled like the one in my Camaro was)

Slightly off-topic: Ditch that Dex-Cool crap. I had to replace my wife's Blazer's Radiator, water pump, and most coolant lines because that garbage turned to sludge long before it's indicated time/mileage. The insidious thing is that the sludge/corrosion buildup nicely matches the color of healthy Dex-Cool so it's tough to spot.


I do not see any valve going into/out-of heater core. Not visible, but did ironically turn the heater on, when it did it...and it stopped, flipped it back to AC (cause it's hot out) and it has NOT reappeared....weird.


DexCool ? Nothing wrong with DexCool as long as you don't let air into the system. I have had perfectly good luck with my truck with 168K on her....even had the dexcool analyzed by lab and it's perfectly clear, not metals, residue or other wise...this dose has 68 K on it...I will flush again just before winter.

Secret to DexCool....keep the puke tank at the proper level and change the cap ...some say to a non AC-Delco...but don't let the cap seal harden to allow air into the system.....Dexcool is not the problem...maintenance may be....I know my daughter had a similar problem and she just never opened the hood for 5 years.....cause the manual said she should have to until the car reached 100K...well it cost her about 1500 bucks....she now routinely checks fluid levels....

Very strange that it spontaneously leaked and then stopped. Problems like that make me very nervous. I'll take a known broken part that I can fix/replace over a mystery part that failed once and then worked again any day.