[73 bird]

Coolant has so much pressure it blows water out when I remove the cap after it has been sitting for days. Doesn't run hot or show any other problems. Water has tiny bubbles coming up. I run distilled water with Water Wetter additive in it.

[Pepi]

Bad cap?

[73 bird]

Changed cap a while back. Still does it.
Drove it for about an hour yesterday. No problems. Opened the cap about 5 hours later and it's still under pressure. Left the cap off all night. Still have tiny bubbles coming up in the radiator this morning.

[dataway]

Battery isn't going dead is it? Sounds almost like some electrolysis taking place in the cooling system. Like a temp sensor that has a short to ground through the coolant, creating hydrogen/oxygen bubbles.

Or some kind of chemical reaction taking place in the coolant that is creating gases.

[Joe's Garage]

To check for an electrolysis problem, take the radiator cap off with the engine cool or cold.

Use your voltmeter to check for voltage by grounding the negative probe to the battery's negative (-) terminal.

Insert the positive probe into the fluid in the radiator. DON'T let it touch the sides or anything inside except the coolant/water.

Check the voltage reading: Anything over 0.1 volts (that's 1/10th of a volt) indicates an issue.

As an example, we had a stray voltage issue with a 1999 Suburban. It was eating up the aluminum radiator's heater hose fitting and the header where it was welded to the tank. The voltage on that one was over 3 volts!!! The coolant was older and was acidic enough to start a chemical reaction that basically turned the cooling system into a 3 volt battery!

Another way to test for and isolate stray voltage is to disconnect your positive battery cable and wait a few hours or overnight. Do the tiny bubbles stop? If they do, battery voltage is getting into the coolant somewhere - quite possibly thru a defective temperature sensor.

Good luck!

[73 bird]

Thanks for the suggestions. Will do the volt meter test tomorrow. Battery is in the trunk. Will it affect the test if I ground to the frame or block?.Cap has been off for over 24 hours and the bubbles are still there.
Guess I could just use an extra piece of wire to get to the battery if it matters.

[Joe's Garage]

The block will work for grounding the (-) probe as long as you have an UN-painted surface and good ground strap(s).

Same goes for the frame - you just need to get past any paint and down to the steel for a good ground.

You might want to use the point where you attach your ground strap(s).

[dataway]

For a quick test, just disconnect the battery, tap the radiator, hoses, engine block with a soft mallet a few times to dislodge any existing bubbles and check fifteen minutes later to see if it's still bubbling ... if it is, hook the battery back up and get out the VOM.

Or pull the wire on the temp sensor. Temp sensor is about the only thing I can think of that would energize the coolant.

[rslarb]

I had the same problem. Recommend draining and flushing the radiator and replacing with purified water and some anti-freeze. There seemed to be a chemical reaction with distilled water and water wetter. That worked for me.

[dataway]

Wonder how this turned out? What ended up being the problem?

[72LuxuryLeMansLa.]

Q. Should I use distilled water as coolant?
A. Yes. But only in a 50/50 mix. Distilled water should not be used as straight water coolant, because it can cause damage to system metals. The reason has to do with how distilled water is created.
During the distillation process, water is vaporized into its gaseous phase, so all impurities are left behind. These impurities include a number of minerals, including calcium and magnesium, the two components of hardness. The water is then condensed back into its liquid phase, so the resulting liquid is pure water. In fact, some of the purest water on earth. The problem is that distillation strips impurities from water, resulting in water molecules that are electrochemically imbalanced. So distilled water will actually strip electrons from the metals in a cooling system as it attempts to rebalance itself electrochemically. This can result in damage to metals in a cooling system.
Using distilled water in combination with 50% antifreeze effectively cuts the amount of distilled water in half. By compounding with glycol, it will not cause damage to metals in a cooling system. For this reason, it is safe to use distilled water in a 50/50 mix.
Q. What type of water is best to use as straight water coolant?
A. Reverse osmosis (RO) water. Rather than stripping impurities from water, RO filters them through a membrane. The resulting water is electrochemically stable, and not harmful to metals in a cooling system. RO water is every bit as pure as distilled water, but without the risk of electrochemical stripping of electrons from system metals.

http://www.norosion.com/tech_coolant.htm

[grandville455]

What ever came of this issue?

[dataway]

Sure wish people would not go away without letting us know how the problem was solved. Could save someone else a lot of time.

[tempest1964]

No chit! I just checked his profile. His last visit to this forum was when he posted on this thread.

[dataway]

Like the old saying goes ... he could have at least taken us to dinner

[Pepi]

Originally Posted by tempest1964

No chit! I just checked his profile. His last visit to this forum was when he posted on this thread.

I looked this morning and saw that too. Hopefully he didn't have any misfortunes that is keeping him from logging back in.

[tempest1964]

You know Pepi, I thought about that too. After I posted. I also hope no illness or injury befell him or his family. As usual, I need to think before I speak.