Valve stem seal job almost done! - Page 2 - PeachParts Mercedes-Benz Forum

rgnprof · #16 06-12-2004, 11:59 AM

exhaust guide:

rgnprof · #17 06-12-2004, 04:41 PM

Ok - I just pulled the vacuum line from the modulator and while I didn't have any AT fluid drip or run out, there had clearly been AT fluid in the line. The bolt that actually attaches the line to the modulator (about an inch long with a hole through it) had AT fluid on it.

Diagnosis anyone? Should this line be completely clear of any AT fluid?

Ryan

ctaylor738 · #18 06-12-2004, 08:37 PM

If it were mine, I would replace the modulator valve.

They are not expensive and it will at least eliminate one source of the smoke.

But with 165K on the engine, you can't rule out (comfortably) worn rings. A quart per 1000 is nothing to get excitied about, though.

joshhol · #19 06-14-2004, 09:36 PM

You must have the 11mm exhaust mandrel since the 9 mm wouldn't fit over the exhaust valve. Maybe the exhaust mandrel was too big for the intake valves, causing them not to seal all the way. Here's a thought though, check your plugs, maybe you can narrow down the leaky cylinder.

rgnprof · #20 10-21-2004, 11:14 PM

Quick update and a couple of quick questions:

I finally replaced the AT vacuum modulator and it helped with the smoking at start-up, but it is not completely gone. So I'm not sure what else could be causing this smoking. The valve stem seals have definitely helped with oil consumption - down from 1 quart per 500-1000 miles to one quart per 2000-2500 miles and my spark plugs look better too. No oil on them and they aren't carbon fouled like before.

I recently replaced the muffler, fuel filter and air filter (with a KLH) and now I have an idling problem - idle is rough especially in gear and surges occasionally - I'm thinking either/both engine mounts and a vacuum problem, (or possibly the KLH sucking in more air??) but I can't find anything for sure. Also, I have a hot start problem and a pretty strong gas smell (really noticeable when I park the car in the garage). I can not find gas anywhere - I have checked and re-checked for leaks, and I have felt the hoses underneath the car and can't find any gas collecting anywhere. This is not really a new problem and I have always thought it is related to my relatively low gas mileage - I get about 11-12 mpg around town. Any suggestions would be helpful - thanks.

Ryan

WANT '71 280SEL · #21 10-22-2004, 12:15 AM

If the eshaust smells bad, maybe it has a fuel mixture problem?
Thanks
David

250 Coupe · #22 10-22-2004, 12:55 AM

There is a chance that the fuel filter change knocked some junk loose and you now have a sticking float in a carb.
As for the smoke still being a problem, you may have some left over fluid in the line that is being pulled into the engine.

Michael

rgnprof · #23 10-22-2004, 10:47 PM

I do suspect a fuel mixture problem and I know the manual says that hard hot starts could be caused by the wrong float level. I have adjusted the floats and changed the needle valves, but I will double check. As far as the mixture, I just can't tell for sure. I do notice that turning the mixture screws really does not make any difference in the idle and I'm still concerned that this KLH filter has screwed up my air/fuel mixture.

ryan

psfred · #24 10-23-2004, 11:53 AM

After-market "high flow" air filters will usually screw up the airflow on a Benz. Put the factory one back on, it's probably less restrictive and will deliver better air flow at high rpm anyway.

If the mixture adjustment doesn't make any difference, you have either a vac leak or a sinking float (lean one way, rich the latter, both outside the range of adjustment).

See if you can rustle up a CO meter to check the mixture properly, otherwise it's gonna pure luck to get it right.

Peter

250 Coupe · #25 10-23-2004, 08:40 PM

If it smells acrid and burns your nose and eyes, it's running lean.
If taking the top off the air cleaner does not change the idle speed the filter is not causing problems, at least not at idle.
You might want to check the plug wires, if you pulled them. It will run with two wires switched but not well.
If you can see gas dripping down the carbs while it's running, the floats are to high.
If you have a fuel return line from the carbs to the tank, it may be leaking where you can't see it.

Michael

rgnprof · #26 10-24-2004, 01:59 PM

Peter and Michael,

Thanks for the replies - I have tried to locate a CO meter with no luck, I plan to make some calls this week. Also, I just put new wires on and I know they are right, although the #1 fits the spark plug very loosely (it's the right angle one). No gas down the carbs, and I have had a leak on the fuel return line right at the triangle shaped valve, but no leak now.

The plugs indicate that the car is not running rich or lean although I definitely pick up on an exhaust smell occasionally while the car is running (maybe a little rich?). I smell the gas after I turn the car off - again, pretty noticeable but I can't find any fuel leaking anywhere.

Am I right to assume that since I have no oil on the plugs that my smoke could not be caused by oil leaking past a valve stem seal and burning out the exhaust when I start the car? This was my first valve stem seal attempt and I have already thought that I may have not properly installed a couple of the seals (to me, this smoke smells more like oil than it did before I fixed the vacuum modulator).

Ryan

psfred · #27 10-24-2004, 07:58 PM

Check the evaporative emission system (charcoal canister) for leaks -- you will get a gas smell if the vapors aren't being pulled off while the engine is running. I've seen GM's with gasoline dripping out of the charcoal canister because the inlet filter was plugged -- supposed to be changed every 30,000 miles and no one seems to know it's there!

In your case, I'd also check the little lever that lifts the carb bowl float vent seal -- if it's bent, out of adjustment, or the seal is missing, you will vent gas vapors under the air cleaner from the bowl vent. It's supposed to be closed with the throttle close, I think.

Peter

rgnprof · #28 10-25-2004, 11:54 AM

I don't think I have a charcoal evap cannister anywhere - I think on this model their is a tube that is located between the 2 carbs and the air filter has a nozzle that fits inside this tube (which is connected on mine). If you know of another evap emission system, let me know where to look.

I'm not sure which lever on the carb bowl float vent you mean? which seal? My carbs do not have the float chamber venting valve (they were eliminated in 1972) - it is all internal venting.

Ryan

250 Coupe · #29 10-25-2004, 02:54 PM

If your looking to buy a CO2 tester check this site out. I have the EZ Bleed and the Digital Gas Tester. Both work as advertised.
http://www.aep.bigstep.com/index.html

Do you have the correct gas cap and if it is a venting type, does it vent properly? If it lets pressure build up in the tank, it could push fumes out some where.

Are the diverters, flaps or whatever they are called in the exhaust manifold working? If they continue to force hot exhaust against the intake it will boil the fuel in the bowls after shutdown. This may lead to a need to crank a bit on startup to refill the bowls and can wash the cylinders down if the fuel runs into the mainfold and past the valves. Check the oil, does it smell like gas? Is it higher than it should be?

Michael

psfred · #30 10-25-2004, 08:52 PM

The charcoal canister, if you have one, will be under the rear seat, outside the car.

In the trunk, there is a small plastic tank and some plastic hoses on the right rear fender. This is the overflow tank (may also be located elsewhere on the coupe, I'm not sure, but in the trunk). Check these hoses and the rubber connectors, and trace down the lines. Vent will probably be either in the rear fender hidden by the bumper (black rubber thing no quite an inch in diameter that looks like a mouting hole minus the bolt) or under the car with a flapper valve, also about an inch in diameter.

If these hoses are bad somewhere, you will get gasoline odors, expecially with a full tank. Ditto for the small lines at the filler pipe.

You must also have a non-venting cap, else you will spill fuel every time you accelerate!

Peter