The short question is fill up the gas tank of 1967 DeVille and pump automatically shuts off (gas level not visible thru filler tube) and a short time later even in 50'F weather the gas mysteriously expands (the expansion rate of gasoline due to heat is not enough alone to drive some of it out of the tank) in volume and gas starts dribbling out filler neck. Tank has all new gaskets, sender, rubber hoses and clamps and does not leak, except out of filler tube. This can't be normal. Has other people suffered thru this? Please read below the history and offer me some advice please - installed wrong by shop A (read below) or me?? It is as if an air bubble maybe gets trapped in there and expands forcing gasoline out of tank??!! The 1969 and newer gas tanks (gas tank for 1965-68 are interchangeable) had two vent ports and maybe that cured this problem if it was a factory design issue.
A well maintained good driving 1967 Cadillac DeVille comes in for a/c work (same Cadillac as starter issue that is now cured - thanks again) and the gas tank leaks-brief history:
The tank was dropped earlier by shop A because the straps were nearly rusted to failure. The straps were replaced by the USA Parts supply product (about 16 ga steel), the rubber hoses were replaced, and the tank was reinstalled all about two years ago. Tank may have leaked before that - not sure, but definitely leaked after that. Only when tank was filled to top would gas leak out of front of tank especially when parked on a slight grade with nose of car lower than aft section.
On to the question:
I dropped the tank and the sender tubes were rusted thru with small pin hole leaks and the tank was very rusted, so I replaced the tank with a good used 1965 tank and new sender. The main difference with a 1965 tank is there are no internal baffles. I made my own straps out 1/8" galvanized and painted them black, exactly replicating the rusted straps in place. Plus purchased new rubber pads between underside of trunk and top of gas tank (used 3/4" thick harness 40, originals looked to be about 5/8" but could not get that thickness). Go to gas station fill car up to top (it is 55'F outside) drive 3 miles home, jack back of car up high - no leaks -thinking I'm good. Park car in 70'F heated garage and eat lunch.
Go out to check on car and gas is leaking out of filler neck (cap is not liquid tight). I pump a pint of gas out so it is 2" below filler neck opening and then I'm good. When I filled up I did not fill it up to that level. My garage is almost level (2" slope over 14'). I just checked on car and all is good, gas about 2" below filler neck. How in the world could gas seemingly expand a good gallon or two and leak out the filler neck????
I did not start driving until 1976 and in Ohio most of the 60's cars were gone. This never happened on 1970 era and newer cars (expect maybe Ford Pintos, my friends brand new 1978 Pinto caught fire while he was driving - a total loss - can you believe it?) Was this common when the car was new? It seems that this would not be tolerated by new owners in 1967 who gas up their Cadillac in advance for a long trip the next day only to find a puddle of gas in garage???
The contents of the tank will expand if the ambient temperature is high.
Check the vent pipe and where the hoses connect to the various fittings.
Bruce. >:D
The ambient temperature is not high, (it is 55'F outside and 70'F inside the garage). The vent pipe tube and hose are new. All rubber and clamps to the tank are new and don't leak.
any ideas??
The 1963/1964s are probably different but, as an idea, several posters at that forum noted:
Comment on November 15, 2012 at 11:33am
I had a similar situation on my 63 several year ago. I filled the tank and fuel was leaking off the tank. Turned out to be the sending unit gasket was leaking, only did it when the tank was packed full. If all the rubber lines are good as others have suggested for you to check, you may need to drop the tank and put a new gasket under the sending unit.
Comment on November 15, 2012 at 11:34pm
I have the same problem ... It's only when the tank is completely full that it smells and the top of the tank towards the front of the car appears wet, no fuel on the ground. Like you I'm not looking forward to draining a full tank. I'm hoping it's just the gasket.
See:
http://6364cadillac.ning.com/profiles/blog/show?id=6543066%3ABlogPost%3A19044&commentId=6543066%3AComment%3A18897 (http://6364cadillac.ning.com/profiles/blog/show?id=6543066%3ABlogPost%3A19044&commentId=6543066%3AComment%3A18897)
Also, Mr. Edge added a small hole at top of vent pipe to his 1964 to stop siphoning and spillage out of the front of the tank.
http://6364cadillac.ning.com/photo/albums/jason-gas-tank-project-august-2009 (http://6364cadillac.ning.com/photo/albums/jason-gas-tank-project-august-2009)
This is all purely speculative but you asked for ideas … what about the gas cap itself (vented v. non-vented)?
http://6364cadillac.ning.com/profiles/blogs/gas-tank-cap (http://6364cadillac.ning.com/profiles/blogs/gas-tank-cap)
HTH
Chris McBride
Problem solved - thanks again to the forum. This was as a result of a wise person replying privately to my e-mail and I wanted to share the answer:
First the sender gasket, rubber hoses, and sender are all new and the tank does not leak. This is evidence because the gas fluid level is about 2" lower than the gas cap and so the entire tank is under a slight fluid pressure and would leak if there was a problem. It has held with no leaks for 30 hours now. The tank only leaks out of the filler cap, no where else as a result of rising gas levels due to thermal expansion.
Expanding gasoline is the problem. This is well documented due to consumer advocacy groups, where the rate of gasoline expansion due to temperature is quite high for a fluid (you pay the same price for a gallon of gas in summer as winter, yet you actually purchase more gas (about 5% more) in winter, and ironically gas is more expensive in summer so it is a double hit. Here is the math:
Gas expands at the rate of 0.069% per degree F.
26 gallon tank, 20'F temperature difference (ground is always 55'F in our area) and we have:
expansion equals (26 gallons)(20'F temp rise)(0.069/100) = .359 gallons, or about a quart and a half. To stop the dribbling out of filler cap only had to pump out a pint. Think if it was 95'F outside we would have a 3/4 gallon expansion. The automatic shut-off on pumps allows a near top off condition in our area.
It takes an hour for the gas to heat up and expand, so fill up when you plan to do some driving, not at the conclusion of it, because if you get 15mpg (fantasy) it will take just 10 minutes to burn thru enough gas that expansion is not an issue.
Thanks again forum!!!!!
Scott,
I don't know where you got your coefficient of thermal volumetric expansion, but by my calculations a 100 degree (F) temperature rise in 20 gallons of gasoline results in an expansion of about 12 fluid ounces.
Greg Surfas
Hiya, Scot. Engineering Toolbox says the VCE for gasoline is 0.00056/F, and for ethyl alcohol it's 0.00061/F. Using 0.000565 for E10 - unless you're fortunate enough to buy all gas - says 26 gallons over a 20F swing should gain 0.294 gallons - slightly less than suggested by the constant you used. A hot day could yield a real mess; maybe the moral really is - don't top off... I wonder what underground tank temps are like in the winter? Yes ground source temp is around 55F but I think the tanks are fairly shallow and surely cool further with extreme weather? The frost line here is about 36"...
On coefficient of expansion, got it from the internet. I started driving in 1976 and this never happened - gas flowing out of filler tube at cap. Do you ever remember this happening in cars of the 60's, you would think not?
I remember back in the 50's & 60's, the fuel would expand and run out the filler neck on a lot of vehicles. Pick Up trucks back in those days had the fuel tank behind the seat. It was common to see fuel running down the outside of the cab below the filler cap when a truck full of fuel was sitting on a parking lot in the sun.
Recently I filled my 63 up one cool morning and drove 7 tenths of a mile from the station to work. It warmed up close to 70 that afternoon. A business neighbor came in to tell me I had gas running out of the back of my car. I sure hated to waste that good premium fuel I spent big dollars for, that morning. ;)
Guys,
Fuel vapors and eve3n leaks were a part of the automobile equation essentially until the "emissions" systems came into play. Tanks were vented to the atmosphere so of course vapors would fill the air when the gasoline temperature got above the vapor point, and often, due to the configurations of the tank vents, gas would "burp" up the vent pipe and started by the syphon action of the (typically) "U" shaped vents. The mid 60's Cadillacs seemed to be especially prone to this. The tanks were relatively flat, wide and the fillers came out close to horizontal, so a full tank could easily slosh gas back out the filler neck and cap.
Scott, I would not trust any everything you read on the internet, and go back to your basic materials science texts, being sure to have the correct units and the decimal in the right place.
Greg Surfas
David,
Thanks, just needed to know if this was normal. This is the only car in our club older than 1970 that is driven regularly and just needed to know if it was normal. I drive my 1970 a lot. If you fill it and drive 2 miles home to stow in garage, after a while the garage stinks of gas, but does not drop gas on floor. If you fill it 7/8 of the way, no smell.
Thanks,
Scot
Scott,
In the 20+ years I had my '66 I learned to live with that exact thing.
Greg Surfas
Greg,
Well if anyone could have cured this it would have been you. Hard to believe that this was reality in such a fine luxury car of the 1960's. Thanks for confirming we don't have some botched installation when tank was first removed that I copied when replacing sender. This is exactly the answer I was hoping for.
My '67 does this as well. I initially thought it was a leaky filler hose.
A thought: Perhaps in the '60's people didn't top off the tank at every fill as we do today with card payment. You probably paid cash and could gauge by the dollar how much the attendant (another change from today) should put in. Therefore expansion leaks weren't as much of an issue.
I always top off my 1958 then drive 1/4 mile to my garage and have never had the type of problem noted. In the 1950's and 1960's we always topped off our tanks; especially, in the winter when gas was $21.9/gallon. Interesting.
I think there is a way to cure this, by installing about a 1/2 gallon aux tank higher than the gas tank behind trunk upper section that has clearance for rear axel that would intercept the vent. It would essentially be a 1/2 gallon bubble in the vent tube so the gas would have a place to go instead of out the vent - it would fill up the little tank, and then drain back into main tank. It would have to be higher than rest of tank so it does not fill with gas and use all the room intended for future gas expansion. There is room in chassis because the exhaust pipe uses this space, and so the tank would have to be like 3" depth, maybe 10" X 8" with hole in bottom (threaded) to accept gas tank vent connection, and hole at top to be the vent. If a fuel tank of this type is sold (Summit racing) I may buy it, install and see if problem is cured.
Scott,
Take a look at the "vapor separators" that were used on the later (70's) emission system equippped cars.
Greg Surfas
Quote from: Scot Minesinger on December 03, 2013, 02:58:37 PM
Go out to check on car and gas is leaking out of filler neck (cap is not liquid tight). I pump a pint of gas out so it is 2" below filler neck opening and then I'm good. When I filled up I did not fill it up to that level. My garage is almost level (2" slope over 14'). I just checked on car and all is good, gas about 2" below filler neck. How in the world could gas seemingly expand a good gallon or two and leak out the filler neck????
You pumped a pint out and it resolved the situation, but are complaining that it expanded a gallon or 2 ?????
Fuzzy math.
And yes Gasoline has a Very high rate of expansion WRT temperature changes.
I have had this problem with my 68 ELDO. The problem is made worse by the fact that the filler tube comes up not much higher than top of the back bumper. On a 56 for example the filler tube comes all the way up under the tail light which is mounted on top of the rear fender.
On the 68 ELDO the top end of the vent tube is attached just below the filler cap. This allows air in the top of the tank to vent out the vented cap but does little for the expansion problem. And the problem is worse when you park with the front of the car a little high.
I’m not sure what happened but I have not had that problem in a while. I do have a couple of spare tanks form a 69 and a 70 with different vent tubes (I think) that I was planning to put in the car. Maybe I don’t need to.
This was, and still is a problem with the 1965 thru 1971, I think, for the RWDs and at least 1967-70 for ElDorados. The fuel filler is behind the lower bumper (or the bumper if its all low) and it isn't high enough.
The best workaround is to not try and jam the tank full, and use a sealed (not vented)???) cap.
on fuzzy math, calculations stated were gas expanded a quart and a half, or 3 pints (this is disputed via incorrect coefficient of expansion), and pumped out a pint, just means that the tank had an extra quart of capacity after pump auto shut-off. It all makes sense.
The 1969 RWD Cadillacs and newer had a metal filler tube connected right to the tank instead of a rubber section, so they are different than 1965-68. Plus there were dual vent lines, one small line broke the vacuum syphon so gas never would exit the vent tube. On Eldorado 1967-70, you probably could interchange those tanks and the 1969 and newer would have the double vent to brake syphon.
I will take a hard look at the "1/2 gallon bubble" in vent tube to see if that works and keep everyone posted with pictures
I had a problem with gasoline odors in my garage when the fuel tank was more than 3/4 full.
A few weeks ago, the fuel system was gone through from gas cap to fuel pump...we removed the tank, looked at it inside (as well as we could, and all was VERY clean and shiny), replaced the filler tube, the vent tube rubber line, the sending unit and sock, and all the rubber hoses from the tank to the hard lines going forward.
No more gas smell.
Funny, though, the new sender reads only about 3/4 full after a fill up. As the miles roll by, I will report whether I have a bubble or whatever.
Frank,
You did the right thing replacing all the fuel lines.
Hindsight being 20/20, in future when replacing sender sometimes you need to bend the wire that holds float so it will read properly. On some cars with tank out of car, and wire extensions you can simulate full tanks and see if float is able to move to top and offer full tank reading. This is a huge pain. The important thing to do is note where gauge is when tank is reinstalled and you add 5 gallons to get to a gas station. The gauge is most useful to avoid running out of gas more than anything else. That full reading on the gas gauge is such a nice feeling though - I get it.
The replacement sending unit is designed around the 67-70 senders which were different than the 65-66 senders, but just the float mechanism. It is marketed as being OK for 65-70 Cadillacs.