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  #1  
Old 03-19-2007, 04:33 AM
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Join Date: Mar 2007
Posts: 4
Help with gearbox and A/C problem

Hello,

I am new to SL ownership. I am very pleased with my purchase an American spec SL380 but I have a couple of problems to sort out.

First the gearbox does not shift as it should. Sometimes it starts in third or fourth (I know they start in second normally), othertimes it just does not kick down when it should, or it takes ages to kick down. It does however change down if I move the lever back to S or if I press the pedal enough to engage the kickdown switch. It will also do quite rough changes if accelerating, changing with a jolt. All this happens sometimes but other times it works just fine.

The second problem is with the ventilation system. In any position (including A/C on) it pours hot air out of the vents.

The last thing is an oil leak from underneath, any common places to start looking?

Any ideas guys?

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  #2  
Old 03-19-2007, 08:16 PM
88Black560SL
 
Join Date: Oct 2004
Location: CT
Posts: 3,510
Quote:
Originally Posted by calypso View Post
Hello,

I am new to SL ownership. I am very pleased with my purchase an American spec SL380 but I have a couple of problems to sort out.

First the gearbox does not shift as it should. Sometimes it starts in third or fourth (I know they start in second normally), othertimes it just does not kick down when it should, or it takes ages to kick down. It does however change down if I move the lever back to S or if I press the pedal enough to engage the kickdown switch. It will also do quite rough changes if accelerating, changing with a jolt. All this happens sometimes but other times it works just fine.

The second problem is with the ventilation system. In any position (including A/C on) it pours hot air out of the vents.

The last thing is an oil leak from underneath, any common places to start looking?

Any ideas guys?
I cant help you with the gearbox starting in 3rd or 4th. As far as kickdown is concerned they always seem to take forever for it to occur. It cant hurt to change fuid an filter, but not a likely cure.

AC check monovalve. There is an overhaul kit available for these for about $30.

Oil leak from underneath. Most likely stearing box. Second most likely is the transmission front seal. Unfortunatly the third most likely is the head gasket, which may look like a rear main seal leak form underneath.

John Roncallo
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  #3  
Old 03-20-2007, 08:35 AM
Super Moderator
 
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,318
It sounds to me like your transmission is on the way out. It is very hard to find anyone to actually fix transmissions because you are looking at 9 hours labor to take it out and put it back in. So you are in it $850 or so to start. Then more often than not, a repair on the "whatever" is made to fix the shifting problem say $300, and it goes back in the car with a new filter and fluid ($100). So the bill is $1250, and 2 weeks later the trans starts to slip, or won't go into 4th or whatever, and the customer comes back mad.

So most shops recommend a rebuilt unit which comes with a warranty when problems like this occur.

I personally wasted $200 on a service with synthetic fluid, then another $250 on a pressure check and adjustment, and $200 on a rebuilt valve body in my disastrous 1981 380's trans. The thing never worked right, and I wasted the money that could have gone toward a $1500 rebuilt trans.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #4  
Old 03-20-2007, 10:34 AM
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Join Date: Mar 2007
Posts: 4
Thanks for the responses guys. I took the car out again today and I found:

The transmission seems to shift way to soon when is cold and as a result the car strruggles in too high a gear. Once the engine was up to temperature it appears to work fine.

I have checked the oil level in the tranny and it was just above the high mark when cold and way above when hot. It looks like somebody has overfilled it.

I put the car on some ramps and with the engine running I had a look underneath. The leak is very slow (a drop every few minutes) and it appears to come form the mesh that covers the torque convertor. Does this point towards the transmission front seal?

I had a look at the vacuum lines. Gosh! it looks quite complicated, not sure where to start.

The car has a new battery but after sitting around for five days it is gone flat. I jumped with my other car and it started fine, drove for 20 minutes and now it starts fine. I guess it must have a short somewhere that slowly drains the battery. Any likely culprits?

The good news is that there is absolutely no rust, the subframe looks almost brand new, the bushes are pretty good as well.

Thanks for the responses so far, I will be very grateful for any further advice. I would like to stick with the transmission for the moment as it is still usable. I will try to change the oil and filter myself and may use some leak stop type fluid. It has to be worth $100 as a first step.
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  #5  
Old 03-20-2007, 12:19 PM
Super Moderator
 
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,318
What year?

If you have a 1981, a very likely electrical culprit is the heater servo. The arm won't move and the motor keeps running, trying to get it to "park" position when the ignition is switched off. Numerous posts on this.


Trans fluid leaks at the front trans seal are very common, as are oil leaks from the engine rear main seal.

It would be interesting to see if draining the extra quart of fluid from the trans made it behave differently.
__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #6  
Old 03-20-2007, 12:35 PM
88Black560SL
 
Join Date: Oct 2004
Location: CT
Posts: 3,510
Quote:
Originally Posted by calypso View Post
Thanks for the responses guys. I took the car out again today and I found:

The transmission seems to shift way to soon when is cold and as a result the car strruggles in too high a gear. Once the engine was up to temperature it appears to work fine.

I have checked the oil level in the tranny and it was just above the high mark when cold and way above when hot. It looks like somebody has overfilled it.

I put the car on some ramps and with the engine running I had a look underneath. The leak is very slow (a drop every few minutes) and it appears to come form the mesh that covers the torque convertor. Does this point towards the transmission front seal?

I had a look at the vacuum lines. Gosh! it looks quite complicated, not sure where to start.

The car has a new battery but after sitting around for five days it is gone flat. I jumped with my other car and it started fine, drove for 20 minutes and now it starts fine. I guess it must have a short somewhere that slowly drains the battery. Any likely culprits?

The good news is that there is absolutely no rust, the subframe looks almost brand new, the bushes are pretty good as well.

Thanks for the responses so far, I will be very grateful for any further advice. I would like to stick with the transmission for the moment as it is still usable. I will try to change the oil and filter myself and may use some leak stop type fluid. It has to be worth $100 as a first step.
Is the oil engine oil black or transmision fluid red. Red is much better than black.

Also

Any good trans shop can R&R this transmission in under an hour.

John Roncallo
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  #7  
Old 03-20-2007, 12:57 PM
Registered User
 
Join Date: Mar 2007
Posts: 4
I am wondering if the leak is just the Tranny spilling out the excess oil. Is there a breather that will allow that to happen?

I have just ordered the filter + gasket so I will know by the weekend. I imagine this is what happens if you let your SL loose on a mechanic that does not know this cars. They probably just filled it to the max mark with the engine not running and cold.
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  #8  
Old 03-22-2007, 09:10 AM
Registered User
 
Join Date: Mar 2007
Posts: 4
Hello,

having done a bit more research it seems that the lack of A/C and the current draw are both probably related to a faulty Servo valve. Can anybody tell me which fuse to pull to stop the servo trying to park and hence the battery going flat?

Thanks

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