Constantly Losing Coolant

[rkevinben]

I wanted to see if I could get some help as my trouble shooting has come to a dead end to this point. I have to add coolant to my 1999 Deville every other day depending on how far and long I drive it. I notice that after driving my Deville I can smell where the coolant is leaking, but there is never a puddle. My car does not run hot, and the thermostat is working cause I can see the temperature rise and fall as the thermostat opens. So through my trouble shooting I had the idea to my over flow hose into a empty water bottle and drove to pick my son up from day care. Total driving time was less than 30 min, and when I got home to check the bottle it was full of coolant. So now I know that the coolant is boiling over and being released out of the hose. Any ideas on what is causing this, or what I need to do so I can fix this? Thanks for any help.

[Cadillac Jim]

There are a number of problems that can cause coolant to go out the overflow hose. Among them:

• A coolant mixture that is less than 50% antifreeze can cause steam pockets in the heads, which will cause coolant loss.
• A leaking radiator cap that does not seal to its rated pressure, 15 psi for your car, will cause steam pockets in the heads and let out coolant from a hot engine.
• A clogged by-pass hose, which runs from the crossover to the surge tank, can cause temperature spikes that result in coolant loss. The temperature spikes can be very fast, but you should be able to see them.
• A clogged heater hose or heater core can act like a clogged by-pass but to a lesser degree.
• The thermostat can stick intermittently and cause temperature spikes, like a clogged by-pass.
• Head leakage can cause steam bubbles to collect at the thermostat; symptoms very closely mimic those of a clogged by-pass or sticking thermostat.

You can eliminate (or verify) head leakage by having your coolant tested for combustion by-products. You can have it tested for having 50% antifreeze at the same time. Also, check for old coolant that is going acid and needs a coolant change.

You can check the bypass hose by taking it off at the surge tank, starting the engine cold and seeing if there is flow out of it at idle.

A leaking radiator cap is hard to see, but a new one is inexpensive. Be sure that it is the right one for your car, that the surge tank seating surface is clean and smooth, and the radiator cap is screwed all the way down (but not too tight).

If the heater and A/C regulate temperature properly, the heater hoses and heater core are probably OK.

[rockfangd]

I would start with a new cap. I find as the caps age they tend to hold as little as 3lbs. supposed to be 15. I dont even test them anymore because if it hasnt been replaced I just get new

[rkevinben]

thanks fellas... went down the the auto parts store... bought a new cap and that fixed the problem... thanks a million... who knows how much money you just saved me...

[rockfangd]

excellent. Isnt it wonderful when a worrysome problem is easily resolved. Wish they all were.

[jndnaps]

That's what happened to mine a year or so ago. Had a bad rad cap too..

[ckent312]

My 2000 is losing coolant as well im going to replace the cap today see if that stops the problem

[Cadillac Jim]

Keep us posed!