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1958 Buick Roadmaster Fluid Leak Mystery


highcking
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In the past I’ve had trouble with a gas leak at the tank gauge when the tank was full. This problem was taken care of over a year ago with a new gauge, seal, and installation procedure. Yesterday I topped off the tank, and later on noticed a fluid leak right below the gauge sender unit. If that fluid were gasoline, I’d have a problem but not a mystery. But I don’t think it is gas. Catching it in a drip pan, I find that the fluid is pale green, has very little odor, is a bit oily to the touch, evaporates slowly, and will combust slowly when touched by flame. All these factors lead me to believe the fluid is antifreeze. (The cooling system has a green mixture.) The gas gauge area is the low point of the tank flange which explains why it overflows the flange there.


The mystery - how is antifreeze getting to the outside top of the gas tank? The radiator is full and I have not driven the car much in months. On the drive to the gas station and back I was making 55 mph which would have blown away anything already in the tank flange. There are no coolant hoses that far back.

 

Ideas anyone?

 

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Joe - when I restored this car a few years ago, it was missing the under seat heater assembly. I looked for one but came up empty and left it out as I had to keep going. No hoses under there. Next week I may let my shop put the car on the lift and search.

 

Love that wagon!

 

Bill

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Interesting theory. No smell of gasoline but it could be mixed in with water. I had a very hard time getting this "under water" gas gauge to seal up. They should have left it on the top of the tank as they did with all Buicks 1957 and earlier. The 1958 design was to help mechanics get at the gauge!

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Hello everyone. I'm the manager of Classic Heaters and Radiators. About 20 years ago, I had a customer come in with a coolant leak in his 66 Mustang. He said it was coming from the gas tank. I went out to his car, saw the leak. I asked him to open the trunk. I picked up the anti-freeze bottle from the trunk, tightened the lid and stood it upright.

 

Also, highcking, the reason that you're unable to locate an underseat heater for your Buick is that nobody makes them... except us. If you're still looking for one, let me know or look at www.ClassicRadiator.com

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John - thanks for the reply. On the trunk — all that’s in there is the very dry car cover for the car. On the underseat heater, I would have gone for it 3 years ago when everything was apart and the interior stripped. It would be a nightmare now.  My immediate unhappy task is to YET AGAIN take off the top if the dash to get at the speedo cable (long story) and a just-recently-broken heater fan switch. This car is like this: fix one thing, two more go wrong.

 

Bill

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Got the Buick on the ramps and determined that leak is definitely coming from the old problem spot, the new and carefully installed tank sending unit. So gasoline is getting out. But why does the leaking fluid look more like dirty water and have no odor? My guess pending further research is that the leaking gas in humid conditions is evaporating on the cold metal surface of the tank and causing it to sweat water on the outside. The dripping condensate is essentially water tinted either by the gasoline itself or by the sealant on the sender unit gasket. I was able to get a little flame from the condensate because the gas is not fully mixed with the water. When this happens inside the tank and is sucked into the pickup, your engine stumbles or stalls. 

 

 

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