Summertime: Gas tank overflow question

[dspeer]

I am a new, proud owner of a 1972 280SE 4.5.

I recently took the beauty to work. It was about 90 degrees, and the sun was shining. For the first time ever I filled her up completely, not remembering that in hot weather you're not supposed to do that.

About 30 minutes later there was a puddle of gasoline under the tank. It was dripping pretty good until I opened the gas tank. The tank was under A LOT of pressure. As far as I could tell it was dripping from the area where the hoses are attached to the tank.

I tried to read up on this but couldnt' find an answer: Is this was it's supposed to do when the pressure in the tank gets too high? If so - where exactly is it dripping from?

If not - what is likely to be the problem? Insufficient ventilation of the tank? How is the tank ventilated anyway? Should I take the tank off completely to find out?

Any response or link to another source appreciated!

Thanks!

[Mike D]

The tank is vented through the vapor recovery canister (black plastic thingy in the trunk behind the spare). It is only vented when the engine is running. (see atmospherically charged fuel injected post I made the other day).

There are two small hoses at the upper right side of the tank which connect to the vapor recovery canister. They are a pretty loose fit and they usually leak from the connection at the tank.

The 4.5 might also have a charcoal canister in the front but it's the rear one which will hold pressure.

[ADP]

Just a question...

Is it a California car?

I have a California 72 4.5 and a whole lotta horror stories about tank venting. Easy solution, once I found someone that knew how to fix it.


Ann

[dspeer]

Thanks for the answer! Maybe I'll just take the tank off or check the fit of those hoses on the tank.

[dspeer]

the car was in Minnesota all its life.
We're having an extremely hot summer here, I guess the car just isn't used to those temperatures....

It was scary - the puddle was about 3 feet in diameter when I discovered it.

What are your horror stories - and do you know what was done to fix it?

[ADP]

Originally Posted by dspeer

the car was in Minnesota all its life.
We're having an extremely hot summer here, I guess the car just isn't used to those temperatures....

It was scary - the puddle was about 3 feet in diameter when I discovered it.

What are your horror stories - and do you know what was done to fix it?

My first 72 280 SEL 4.5 had a ventilation valving system which is located in front of the rear wheel. It was non operational because it was filled with dirt and caused all sorts of havoc.

I believe this is Cal specific, and does not apply quite the same way to your car.

The horror story was that it took more than one shop to figure it out, the car reeked of gas fumes at various times and my friends made lots of jokes about spontanous combustion.

Eventually my gas tank split at the seam - and I'd find that 3 foot puddle if I put more than 1/2 a tank of gas into it.

Please don't assume that this is your problem. My second car, same year and model, but east coast, doesn't have the same system at all!

Still, I live in Atlanta - and it gets plenty hot here, and nothing leaks from my fuel system.

I'd get the car up on a lift and check out all the fuel system hoses around the pump. Also, the sensor unit for the gauge seals through the trunk - I don't know if you had a full tank when this happened.

Lastly, if you just got the car - do you know what shape your fuel hoses are from the injectors to the ring line, and the rest of the rubber in the ring line?

***This has nothing to do with the puddle under the tank - this is just one of those finicky things about 4.5s and their fuel injection that we all learn. The hoses are rubber and are exposed to a fair amount of engine heat, they crack, leak and cause fires... Not to scare you or anything, but someone told me a long time ago, and I'm telling you!***

Ann

[Tomguy]

The only way gas can leak from a 4.5's system is a leaky fuel line or gas tank.

Vapors can leak out, and often do if your vapor recovery system is bad, but even if you fill it entirely fuel shouldn't leak!

Replace any fuel hose you see. And all of the lines except the ONE before the pump should be HIGH PRESSURE EFI hose and NOT "Fuel hose" - there is a difference, and you don't want to learn the hard way what it is. Basically, any fuel line in front of the pump will be under a constant 30PSI. This includes all the under hood lines and the metal fuel rails.

[dspeer]

So I guess one of the next weekends I will be taking off the tank and see what it looks like. I am getting about 9 miles/gallon, so I guess there will be some rebuilding and adjusting, and doing this starting with the tank makes a lot of sense, I guess. When the leak happened, I immediately siphoned about a gallon into a bucket, a large portion of that being water. And the readings from the gauge are questionable at best.

One of the first things I checked was the fuel rail and everything rubber connected to it, and everything looks good.

Thank you for all your help and expertise!
This forum is amazing!

[ADP]

My tank split in the seam because the vapor recovery system caused a condition to occur where there was enough vacuum that it sucked in the tank. You could hear air being sucked back into the tank when you took the gas cap (which was correct) off. Thank you California emissions...

The thing that makes me think leaky tank is you mention in your first post ..."filled her up completely..." Gee, I remember doing that!

I'm glad Tom mentioned EFI as opposed to generic fuel hose.

And as for your mileage - this can be a number of things. In my current car, the gas gauge, even with new sending unit in the tank, can be kinda flakey as well. I pretty much calculate my mileage from the odometer and how much gas I put into the car.

Mine got about 9mpg as well when I first got it. Driving it up from Florida to Atlanta, we couldn't pass a gas station. Now she is up to about 16mpg around town - and even better on the highway. Of course I've replaced injectors, injection wiring harness, distributor and trigger points, plus a tune up and a lot of tweaking.

What always amazes me about these cars, from the first 4.5 I got in 1992, is how well they run in some amazingly misadjusted and neglected conditions.

I'm about to pick mine up from my mechanic, who just made my AC work, among other things.

Ann

[dspeer]

The more stories I read about broken or even just dirty tanks, the more I want to take everything gas related between rear bumper and engine off and either fix or replace it. The local MB dealer tells me that there are currently 8 brand new W108 gas tanks in the country, one of them could be mine for a mere $740. Add another 60 to that, and I could eliminate gas supply as a problem. I also noticed that the tank has quite a bit of rust where it mounts to the body.

The previous owner used it as his winter car (!) which here in Minnesota means it drove on 50% snow and ice and 50% salt.

I too am amazed that this car runs and drives. It seems like everything that broke always got fixed somehow, because somebody depended on it for transportation. Other than that nothing was done. The windshield is cracked, not working are: a/c, central locking, odometer, emergency brakes, heater, interior light switches and on and on.

And even in that sorry state the kid's eyes light up when I tell them they get to start it and take it for a cruise.

[ADP]

Can I make some suggestions? If you've already done this, please disregard.

1. Evaluate your new baby nose to tail. Make a list of everything you think is wrong.

2. Depending on your skills/resources, take her to a competant Benz mechanic who knows this car pay him to check it over. Compression, suspension, major rust evaluation.

3. Figure how much you have to spend and how much it needs. Be absolutely worst case scenario on the $ figure for what it needs. Now add 1/3 of the total of what it needs, to the original sum.

I'd love to just write a check for a tank!

Seriously. I don't want to be the harbringer of doom but sometimes I think "oh my god how much did I just spend?"

But today when I picked up my car from my mechanic on a 91 degree traffic from hell friday in Atlanta - and ran errands (and was cool as a cucumber) and she ran like a top, oh man - this is so satisying.

Every little repair, everything I put right, is a real pleasure to do. My mechanic does a wonderful job and he is just as pleased as I am at how well she runs these days.

If thats what you are looking for - and don't mind spending what seems like silly money sometimes, welcome to the club!

I got my current car last April - the other one is too far gone and is a parts donor. This is my litany since April - and this is the edited for brevity version.

Resolve timing chain issue (was one tooth off) replace tensioners.
Complete tune up and fluid replacements with proper spec fluids.
Readjust too tightly adjusted valves.
Transmission service.
Replace some oil lines and rotten fuel lines near the tank.
Replace fuel sensor in tank.
Replace dash lights.
Replace all my fuel injectors with rebuilt Bosch units.
Replace my fuel injection wiring harness.
Replace my distributor and trigger points with the one from my parts car.
Replace my front windows regulators and motors from my parts car.
Repair temp sensor wiring for fan.
Replaced inoperative electric Hirschmann antenna with manual one from my parts car.
Send Becker Europa off to Becker for rehab and Ipod conversion, install new speakers behind old enclosures.
Repair vacuum door system.
Replace door lock mechanism from parts car.
Replace AC compressor and receiver dryer, get custom AC hose made, flush system from abortive 134a conversion, fill with Freeze 12.
Leatherique interior.
Replace ragged sheepskin seat covers with custom new ones.
Replace glove box latch with new one, salvage glove box from parts car.
Replace all corroded fuses and clean fuse box.

This is what I have left...
Kingpins, some rubber/tie rod ends, subframe mounts (the lower control arms are ok)
Rust repair underneath (trip out to very spendy, but very good Bud's Benz).
New muffler.

Suspension stuff is waiting for cooler weather as its not that bad and my mechanic's shop isn't air conditioned!

Eventually I'll need a top end and a transmission and I'd like to repaint her as well.

And its not just me. I got a huge folder from the previous owner, who was friends with the first owner. I've got lots of the original records. Having a parts car really helps - but I've been hauling that car around for 15 years!

Ann

[dspeer]

That's an impressive list indeed. I am sure that if I looked at this car front to back, I would be able to come up with a very long list too.

I grew up in Germany. In my town, rich people drove those when I was a little boy. And I remember how fascinated I was by somebody actually moving the license plate out of the way in order to fill the tank.

When I look at Craigslist or ebay, I know I could get a 280SE in much better shape for far less than what I'll end up putting into it. My mechanical abilities are limited, I would have a rough time fixing the emergency brakes even with all the handbooks I already bought.

I will have a body guy take a look at this baby next week, and I will also have the compression checked. If those items check out fine, I will go ahead with it. It's not about having a shiny, cool car. It's about taking all door panels off to check the vacuum units that make the central locking work and fixing what needs fixing.

It's not the shiny car, it's about the process that gets me there.

Dietrich

[ADP]

Hey Dietrich

Originally Posted by dspeer

That's an impressive list indeed. I am sure that if I looked at this car front to back, I would be able to come up with a very long list too.

Actually - thats a much shorter list than a lot of other people start out with. I've seen some before/after photos and read accounts of rehab/rescue/restoration that are incredibly complex. I started out with a car that was in basically, pretty good shape. My first one wasn't.

Originally Posted by dspeer

I grew up in Germany. In my town, rich people drove those when I was a little boy. And I remember how fascinated I was by somebody actually moving the license plate out of the way in order to fill the tank.

I'd always wondered exactly how the early 70s SELs fit into the general scheme of car ownership in Europe. I know they were the original S class, I know that there is only one body style larger, but I wasn't sure if they were the European Caddy of their day, or something even higher class.

My 73 Camaro had the gas tank access under the plate too

Originally Posted by dspeer

When I look at Craigslist or ebay, I know I could get a 280SE in much better shape for far less than what I'll end up putting into it. My mechanical abilities are limited, I would have a rough time fixing the emergency brakes even with all the handbooks I already bought.

I'm not a mechanic either. I've got some automotive background and a pretty good understanding of how things work, but I know that with my free time, resources and abilities vs. an actual competant mechanic's time, resources and abilities, for most everything - its better for me to pay someone else to do it. I'm not afraid to disect my parts car and I've got the factory manuals for my car - but I pretty much stop there!

Originally Posted by dspeer

I will have a body guy take a look at this baby next week, and I will also have the compression checked. If those items check out fine, I will go ahead with it. It's not about having a shiny, cool car. It's about taking all door panels off to check the vacuum units that make the central locking work and fixing what needs fixing.

Good plan, good thinking!

I'm not approaching this as a restoration. I'd prefer to think of what I'm doing as preservation.

I'd like everything to work and not have holes in it, but if my chrome isn't perfect, my paint a little tired, my interior a little worn, thats ok. Still, I'd like to listen to the radio, not swelter, be able to open, close and secure the doors, see the speedometer at night, not tear my pants on the seat springs and know that my car isn't going to die on the interstate - I'm happy.

Originally Posted by dspeer

It's not the shiny car, it's about the process that gets me there.

I agree!

Ann

[dspeer]

Hello Ann:

I think if I seriously sat down with a piece of paper and a pencil and wrote everything down, I would probably be able to come up with a very long list too. But looking at some of the postings in this list - there are a lot of issues that my car doesn't have. The interior only has a couple of issues - one of the armrests is broken, and the headliner came loose in the back.

Almost all vital functions are working fine. That's probably because it was driven daily until not too long ago. I found the Benz on a independent dealer's lot in a small farming town. The other cars on the lot were all tired American cars from the 80s and early 90s.

I am not entirely sure if I should only fix (or have fixed) what's broken or take apart one system after another to bring it up to a better state of functionality. We'll see.

I grew up in a middle class family - the first car ever, an Opel Kadett (GMC), was bought in 1964, before that nobody in the family could afford one, which was pretty typical. In 1972, beetles were still by far the most popular cars on the road. If I'm not mistaken, the 280SE was never sold in Germany with the 4.5 engine. Gas has always been way more expensive there than here. And in the 60s and 70s driving a Mercedes, let alone a S class, was always considered the biggest luxury imaginable.

By the way: after the usual evening cruise of 5 miles, I opened the trunk, and it just stank like gasoline. So the gas tank and lines will get some very close attention very soon.

Dietrich