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1991 300E24
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132 Posts
Discussion Starter #1
Hi, just bought a 1986 300SE I couldn't find all the answers I needed, hopefully you can help?

Firstly, the efficiency meter sits in the middle of the gauge in idle, is this normal? (I've heard that the vacuum lines may have something to do with it?)

Also, the rear left wheel makes a sort of scraping noise while driving and I've noticed it gets quite hot after driving. (Perhaps the brake is jammed on?) Does anyone know what I could do?

Thanks
 

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1984 500SEL
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91 Posts
the economy sitting in the middle is indicative of a vacuum leak. scraping wheel could mean warped rotor or stuck caliper, worn out pads... was the car sitting for a long time before you started it and the brakes rusted or? Nice picture, she looks pretty :) good luck.
 

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1993 300TE, 1995 E320 Wagon
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1,895 Posts
+1 on the nice-looking car!!

If this car did sit for a while, you'll be better off replacing stuff bit by bit-- as much as your budget can afford. Hopefully you set aside a bit of cash for this eventuality.

The vacuum lines are not terribly hard to replace-- you might spend an hour counting up all of the rubber joins you can see, and then estimate the length of the various tubes involved. The tubing and joins are cheap-- I'd guess something like $50 would take care of the majority of them. Another thing might be the brake booster line-- it has a valve in it that sometimes craps out, and there's your vacuum leak.

As to the noise/heat on the rear wheel, it does seem like a stuck caliper right off the bat, but another possibility would be the parking brake or a wheel bearing-- either would cause noise and heat like a stuck caliper. Hard to say what's the best approach-- I'd definitely want to remove the rear pads on both sides and then try and rotate the wheel/rotors. If they are smooth and no noise, then you have a sticky caliper. If they are still grinding, then it's either the parking brake or a bad wheel bearing. In the case of a wheel bearing/parking brake, I'd want to remove the rotors on both sides and go ahead and replace the bearings (not terribly expensive) and replace the parking brake shoes; perhaps consider replacing the rotors at the same time. If it's a caliper, then I'd buy a pair of rebuilts and slap them on. You don't want an old caliper on one side and a new one on the other. Lastly, you might also replace the rubber brake lines. Nothing like a set of new brakes on an older car, just to have that confidence while driving. If you were to replace the whole set in the rear, including bearings, rotors, pads, shoes, lines, I'd estimate $125 to $150 per side in parts, depending on the source.

Have a look at Autohaus AZ for some quick prices. Where are you located? It looks as though you're in the UK(?) or Australia(?) (right hand drive) so I don't know what kind of prices you'd be looking at there.

http://www.autohausaz.com/

There are probably several members here on BW from somewhere near you to check out-- You might shoot a message to one of them just for some suggestions as to parts and/or mechanics.
 

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MB 1985 W126 300SEL, 1991 MB W124 260E, 2007 MB W209 CLK200, 1999 Skyline R34 GTT Veilside,
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342 Posts
I Just serviced the calipers by changing the seals. Pls check what brand of calipers before buying the seals. Mine is a 300SEL and the front were Bendix and the rear is ATE. I had terrble vibration shudder when press the brake pedal slightly when high speed, after opening for the reseal, notice a broken cyclinder in the rear. ATE only sells complete units so i had rear left side changed new meanwhile waiting for the right side parts to arrived.

Best to changed all 4 rotors with pads since they are resonably cheap for assuarance.

Anyway I think i have the same vacuum leak and intermittent ticking on the oil pressure gauge. Can vacuum leak cause both gauges to react like this...
 

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1991 300E24
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132 Posts
Discussion Starter #8
Just had a look today and the rear brake pads are worn right down so I’ll replace these and see if this corrects it.

Thanks for the advice ElRojo, I’m located in New Zealand.

Driftmeister, my oil pressure gauge is a bit funny as well so I would say it is the vacuum leak.

Would the post regarding Engine Vacuum Diagrams below be applicable to my 300se? (I’m pretty sure it is, just got to check..)

http://www.benzworld.org/forums/w126-s-se-sec-sel-sd/1340751-do-yourself-diy-repair-thread-wheel-5.html#post2561883
 

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'73 450SL, '83 300CD, '01 E320 4matic
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2,446 Posts
The oil pressure gauge on these models has an electronic sending unit which can get gummed up and need to be replaced in time. If the oil pressure gauge is giving an erratic reading, chances are the sending unit (transmitter in MB speak) could need replacing. An erratic idle can also cause a fluctuating oil pressure gauge.

A ticking in the cluster is typically the odometer gears if you're hearing it only while the car is in motion.
 

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1991 300E24
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132 Posts
Discussion Starter #10
It turns out it was a stuck left calliper. Rebuilt both rear ones for only about $100NZD, so a bit cheaper than brand new.

Left side pads were quite worn..


Next thing is that the tachometer isn’t connected, how would I fix this? Can I?
 

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1984 500SEL
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91 Posts
The oil pressure gauge on these models has an electronic sending unit which can get gummed up and need to be replaced in time. If the oil pressure gauge is giving an erratic reading, chances are the sending unit (transmitter in MB speak) could need replacing. An erratic idle can also cause a fluctuating oil pressure gauge.

A ticking in the cluster is typically the odometer gears if you're hearing it only while the car is in motion.
Hmmm, not to take the thread in a new direction. but how does that trasmitter work? Where is it located? I've noticed this in my car, as randomly the oil pressure gauge will shudder. The gas gauge does the same thing, but I've already found the cause of that. Any help would be appreciated.
 

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1989 300SE (Rear Ended & Junked) 1995 E420, Fully Loaded with Ortho Seats & Rear Sun Shade :)
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503 Posts
The vacuum lines are not terribly hard to replace-- you might spend an hour counting up all of the rubber joins you can see, and then estimate the length of the various tubes involved. The tubing and joins are cheap-- I'd guess something like $50 would take care of the majority of them. Another thing might be the brake booster line-- it has a valve in it that sometimes craps out, and there's your vacuum leak.
Can somebody please guide me? I am having similar problems and trying to find the source of a rough idle and a vacumn leak.

1. The valve - What part # would that be or would I have to replace the entire booster line? I am replacing the brakes and might as well change that too.

2. If I am changing the vacumn lines, how many metres would I require? Is it advisable to change all the lines after 20+ years or just change the piece which is affected?

Thank you in advance for the help.

Cheers
 
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