highcking Posted December 16, 2021 Share Posted December 16, 2021 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? Link to comment Share on other sites More sharing options...
EmTee Posted December 17, 2021 Share Posted December 17, 2021 Is the car losing antifreeze (seems the answer should be 'yes')? Is there any evidence of antifreeze in the engine compartment? Look at water pump and radiator overflow tube. If antifreeze is leaking while the car is being driven, it could be blown back under the car and accumulate almost anywhere. It would then drip to the ground when the car is parked. Does the car have an under-seat rear heater core? If so, I think those lines run under the car and a leak could spray antifreeze back to the gas tank while driving... 1 Link to comment Share on other sites More sharing options...
Bill Shields Posted December 17, 2021 Share Posted December 17, 2021 No underseat heater on this car. Coolant is showing full but I only drove the car 10 miles or so. I looked under the hood and saw nothing, water pump is a new installation as are all the hoses, clamps, etc. I didn't have time to run more tests, I'll get at that this weekend. Link to comment Share on other sites More sharing options...
EmTee Posted December 17, 2021 Share Posted December 17, 2021 9 hours ago, Bill Shields said: water pump is a new installation as are all the hoses, clamps, etc. Could be a loose clamp; I'd check each one to make sure they're still snug. Link to comment Share on other sites More sharing options...
Wayne R Posted December 17, 2021 Share Posted December 17, 2021 (edited) Emtee---you will be correct---after new hoses are fitted it is not unusual after about a month for some to require tightening up again.--it happened to myself just a couple of months ago ,on my 64, after i replaced all heater hoses. Edited December 17, 2021 by Wayne R (see edit history) Link to comment Share on other sites More sharing options...
60FlatTop Posted December 17, 2021 Share Posted December 17, 2021 You can pressure test the cooling system. I have a pressure tester and check mine every Spring. It shouldn't be too hard to find a shop that would pressurize and look the system over for you. Link to comment Share on other sites More sharing options...
avgwarhawk Posted December 18, 2021 Share Posted December 18, 2021 (edited) Evaporates slowly? Antifreeze does not evaporate to my knowledge. Check the heater core is not leaking on the floor boards and finding it's war to the gas tank via hole in the floor.. Edited December 18, 2021 by avgwarhawk (see edit history) Link to comment Share on other sites More sharing options...
Mudbone Posted December 18, 2021 Share Posted December 18, 2021 Are you sure it is not brake fluid? Link to comment Share on other sites More sharing options...
Bill Shields Posted December 18, 2021 Share Posted December 18, 2021 That occurred to me also. I don't think so. I now have an oil splash pan covered with the clearly green fluid. Putting it on painted surfaces had no effect. And the gas tank is well behind the rear brake lines. Link to comment Share on other sites More sharing options...
Bill Shields Posted December 18, 2021 Share Posted December 18, 2021 Updated report. The car has been sitting in the garage for two days and the greenish fluid still drips from the gas tank flange. The big oil splash pan is now covered with a thin layer of fluid. I'd guess if I poured it out there would be maybe 4-6 ounces. So far no noticeable drop in the radiator level though that amount of fluid wouldn't make much of a dent at the radiator. I am ruling out "splash back" from driving at high speed, that would have left fluid all over the bottom of the car. No sign of that. On evaporation -- the pan fluid does not seem to be evaporating now that the temp is cooler. My impression is that there is some water mixed in with whatever is dripping. No smell of gasoline. This weekend I'll put the rear end up on ramps and take a look. The forward slant of the body should drive the dripping to another location. I can also run a cooling system pressure test -- I have one of the old Stant kits for doing that. Thanks for all the replies! Link to comment Share on other sites More sharing options...
old-tank Posted December 18, 2021 Share Posted December 18, 2021 Look in the trunk ... 4 1 Link to comment Share on other sites More sharing options...
Bill Shields Posted December 18, 2021 Share Posted December 18, 2021 Wow, I hadn't thought of that. I'll check tomorrow. There should be nothing liquid in there! 1 1 Link to comment Share on other sites More sharing options...
old-tank Posted December 19, 2021 Share Posted December 19, 2021 So who is the OP @Bill Shields or @highcking? No update here, but apparently on another forum. Straighten it out or both of those "users" will be added to my "ignore" list! Link to comment Share on other sites More sharing options...
highcking Posted December 19, 2021 Author Share Posted December 19, 2021 My question was posted on two forums. If that is against any rules, I apologize. I don’t know about the @ business. The answer is that gasoline is in fact leaking slowly at the tank sender. But the gas is evaporating on the cold metal, causing a watery condensate to drip that has no gasoline left in it. Odd phenomenon. I’ll have to go after the sender unit seal yet again, or just never fill the tank over half full. Link to comment Share on other sites More sharing options...
old-tank Posted December 19, 2021 Share Posted December 19, 2021 1 hour ago, highcking said: My question was posted on two forums. If that is against any rules, I apologize. I don’t know about the @ business. The answer is that gasoline is in fact leaking slowly at the tank sender. But the gas is evaporating on the cold metal, causing a watery condensate to drip that has no gasoline left in it. Odd phenomenon. I’ll have to go after the sender unit seal yet again, or just never fill the tank over half full. Post where you want but please😂 update all forums. No rules against using multiple identities but it just confuses old people like me. 1 Link to comment Share on other sites More sharing options...
Ben Bruce aka First Born Posted December 19, 2021 Share Posted December 19, 2021 2 hours ago, old-tank said: Post where you want but please😂 update all forums. No rules against using multiple identities but it just confuses old people like me. Grouch!😁 Ben 4 Link to comment Share on other sites More sharing options...
56 Buick Posted December 20, 2021 Share Posted December 20, 2021 I had similar leaking issues. I suggest using the rubber infused cork style gasket as these seem to best avoid leaking. Link to comment Share on other sites More sharing options...
highcking Posted December 20, 2021 Author Share Posted December 20, 2021 That’s what’s on there now! I had leaks with the thin neoprene type so I switched to the cork style. This worked well for the past year, until the latest tank fill up. It may just need a SLIGHT turn on the screws. Thanks for letting me know it works for someone! Link to comment Share on other sites More sharing options...
56 Buick Posted December 20, 2021 Share Posted December 20, 2021 Ah but is it cork or rubber infused cork. There is a difference as the cork alone will not be as hardy. Link to comment Share on other sites More sharing options...
highcking Posted December 20, 2021 Author Share Posted December 20, 2021 Good question. Where did you buy the one you’re using? Link to comment Share on other sites More sharing options...
highcking Posted December 20, 2021 Author Share Posted December 20, 2021 Danchuk 1955-1957 Chevy Gas/Fuel Tank Sending Unit Gasket, Nitrile & Cork, Also 1953-1960 Corvette (Best) Item Number: 195D Your Price: $4.05 EA In Stock Qty: Link to comment Share on other sites More sharing options...
56 Buick Posted December 20, 2021 Share Posted December 20, 2021 That certainly appears the same as I used. Link to comment Share on other sites More sharing options...
highcking Posted December 20, 2021 Author Share Posted December 20, 2021 I think that’s what I used also. I put gas resistant sealer on the screws and tightened the assembly down VERY carefully. I plan to siphon down the tank and let my shop take a look. Link to comment Share on other sites More sharing options...
56 Buick Posted December 20, 2021 Share Posted December 20, 2021 Only difference then is that I didn't use sealer. I recall making a decision not to do so after reading somewhere I shouldn't. But who knows what is correct. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now