Question about Mercedes-Benz 300-Class

1 Answer

1980Mercedes 300SD....reviving car been sitting for 5 year s...power brakes not operating reliably....found vacuum leaks...closed off one tube going to open end somewhere....what vac. should the pump pull...also need map of vacuum system ?

Posted by on

  • Max G Schoenfeldt May 24, 2011

    I am not sure of body designations...this is a four door turbo sedan....Yes the manual would be great.,...thanks Max



1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 10 achievements.


    An expert that got 5 achievements.

    Brigadier General:

    An expert that has over 10,000 points.

  • Master
  • 3,489 Answers

You should be pulling about 29 inches of vacuum depending on how far above sea level you are. I have 2 or 3 manuals I can send you that are Genuine Mercedes manuals. Let me know. I can send them via email This would be a 123 body correct?

Posted on May 24, 2011

  • Kori Policy
    Kori Policy May 24, 2011

    Email me and I will send them right to you.



1 Suggested Answer

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

a 6ya expert can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
New users get to try the service completely Free afterwhich it costs $6 per call and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.

Posted on Jan 02, 2017


Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

1 Answer

How to rebuild, and where to get parts to rebuild door lock vacuum pump on a 1981 Mercedes 300SD. It is located in the trunk.

Hi,just go on u-tube and type in mercedes 300sd door lock vacuum pump repair,it shows you how to test and also to test the door actuaters,hope this was some help all the best.

Nov 04, 2016 | Mercedes-Benz 300-Class Cars & Trucks

2 Answers

How to diagnose a bad brake boosterOn my 95 GMC Suburban K 1500 4 x 4 5.7 v8

Hi, your basic symptoms will be. Your brake pedal. Will be very hard to push. When the pedal is engaged there will be a large vacuum leak, usually causing the engine to be very ruff or stall. If its bad enuff, youll hear the the air leak when pedal is depressed, hope that helps.

May 02, 2016 | GMC Cars & Trucks

1 Answer

Occasionally when you first start the car the brake pedal will barely move and it is hard to stop the vehicle when rolling in the driveway, like the power brakes aren't working.

Power brakes are operated by engine vacuum. It sounds like you may have a leak in the power brake vacuum system, so when the engine isn't running, the vacuum leaks away, and you have no "power" in your power brakes. Once the engine is running, the vacuum is built up over several seconds, and you have power for braking again.

I would check the vacuum lines for cracking and the power brake module for vacuum leaks.

Jun 08, 2015 | 2006 Saab 9-3 Aero

1 Answer

Oil in brake booster

The vacuum is created via a mechanical pump driven from the cam, Or a separate, electrical pump.

The only liquid I have ever found in any servo (booster) is brake fluid from a leaking master cylinder.
If the vacuum is low/absent, due to a faulty cam driven vacuum pump, and crankcase pressure rises, along with a faulty one-way valve in the vacuum plumbing, it's possible the oil could be forced into the servo housing, and operating the brakes would help it happen as the servo could act as a pump itself and draw oil from the engine.

Found some diagrams:

What colour is the oil?

Nov 08, 2013 | 1999 Saab 9-5

1 Answer

High rpm after putting in drive

first.... is this when the engine is cold or at operating temp. or does it make a difference.
it would help to know what make model and year, that being said, high idle is generally caused by vacuum leak somewhere or dirty throttle body . does it have a vacuum brake booster or power steering brake booster?

Mar 30, 2013 | Chevrolet Silverado 1500 Cars & Trucks

3 Answers

Are there vacuum hose on the brakes hydraulic system?

NO. the vacuum is used to make the brake pedal easy to push, power brakes. the pedal would be hard without vacuum, that is why the pedal gets hard with the key off and engine not running. the problem you are having is more of a hydraulic problem.
Have the brakes checked asap. the brake system may have a leak causing the pedal to go low. check the fluid level and if it is low or empty then there is a problem, could be a rotted brake line leaking or a wheel cylinder leaking.

Dec 07, 2012 | 1997 Ford Probe

2 Answers

2173 error code on 2006 dodge magnum 3.5 liter HO 6 cylinder?

A large vacuum leak is most likely the cause of this DTC.
Inspect the Intake Manifold and Throttle body for leaks and cracks.
Inspect the Power Brake Booster for any vacuum leaks.
Inspect the PCV system for proper operation or any vacuum leaks.
Inspect the MAP Sensor for proper installation.

Jan 07, 2011 | Dodge Magnum Cars & Trucks

2 Answers

While sitting at lights even pressure on brake pedal. brake pedal sinks to floor . engine revs drop to 600 rpm's . when brake pedal is released engine rev's increase to 900 rpm's? Dealer mechanics say it...

not normal at all,a couple of causes 1 small valve at the front of the servo unit,2busted pipe coming from the servo unit,3the servo unit itself needs where is the servo unit?.if you lift the hood you will see in front of the brake pedal only inside the engine compartment look closely and try to judge it ,its about the size of a bottom of a small sauspan only about 4/5 times the thicknes,thats your servo and that where your problem is.adrian,,,

Dec 03, 2010 | Dodge Dakota Cars & Trucks

2 Answers

List items for service at 5 year service interval

Maintenance must be carried out at 16 000 km (10 000 miles) or 12-monthly intervals from date of delivery, whichever comes first.

Renew engine oil and oil filter.
Renew drain plug sealing washer.
Renew drain plug assembly.
Visually check underbonnet/underbody
for any fluid leaks.
Inspect brake pads for wear (brake disc
condition on pad change).
Renew coolant.
Renew spark plugs (Normally Aspirated). 112 000 km (70 000 miles)
Renew spark plugs (leaded fuel markets only).
Check accessory drive belt tension wear indicator(s) – replace belt(s) if necessary.
Renew front accessory drive belt. 160 000 km (100 000 miles)
Renew rear accessory drive belt. 112 000 km (70 000 miles)
Check/top-up brake fluid level.
Check/top-up coolant level.
Check/top-up windshield washer reservoir.
Check/top-up power steering fluid level.
Check/top-up battery electrolyte level.

Apr 29, 2010 | 2004 Jaguar X-Type

1 Answer

Trouble starting, runs rough when it does start. New distributor, New plug wires, repaired master relay

Lets face it the car is now 19 years old and prbably has been pretty reliable up to this point. Things happen to older cars that need a little TLC to bring them back into a good operational status.

There are few thing you should check
1. The EGR valve
There is a very good possibility that your EGR valve is coked up with carbon and is not closing all the way. The only way to know for sure is to remove the valve from the input / output metal tubing and mount. Then perform a visual inspection of the valve AND the tubing. Everything tends to get clogged with carbon and soot over time and needs to be cleaned up. You may even need to replace the EGR valve if the diaphram does not function properly. (Oral Test with a vacuum line) This can be done by 2 people. onde drawing a vacuum on the diaphram and the other forcing air through the cleaned up valve where the tubing mates. In a static condition no air should pass thru the valve. With a vacuum applied to the diaphram air should flow freely through the valve.

2. Compression test.
On a 19 year old car the valves have a tendancy to start to allow cylinder compression to "blow-by" the valve seats when closed. The only way to really verify this is via a compression tester. An engine takes a minimum of 100 PSI to start. However a healthy engine should read between 125 - 150 PSI.

3. Timing belt.

The timing belts over time get hard and start wearing. They sometimes lose belt teeth, crack, or become loose. A loose belt would cause the car to not maintain a constant speed at highway speed. (Hunting speeds with fixed accelerator position) They can also cause the engine timing to change by jumping a tooth and result in very poor engine performance.

4. I note a new distributor and plug wires. How about the spark plugs are they also new? If it is running the same as before, (poorly) with new plugs then paragraphs 1, 2, and 3 all apply. Something to note... In the last year I have come across 2 sets of bad spark plugs that both had 2 defective NEW spark plugs in the set. (Boy does that throw you for a loop!) One set was NGK the other was Bosch!

5. Another thing that happens to a 19 year old car is that the vacuum lines get hard and crack at the connecting points. Check all of the lines all over the engine. I know your Honda has loads of them. There is also a Vacuum manifold / cannister mounted on the firewall close to the brake master cylinder that you need to listen to for leaks. These don't fail often but when they do.... it can take a long time to isolate and determine that it was the source of the problem.

Hopefully you have a very good ear and can hear the leaks if there are any. Some places are just hard to access. In those areas.... a hand held propane torch (unlit) is an awesome tool in locating vacuum leaks. If there is a leak the engine will speed up as you pass the torch near the leak. Just be aware of the fire danger and hopefully you have a portable fire extinguisher available in the event of fire. All you have to do is barely open the valve on the torch... it does not have to be fully open. (Safer too!)

Wish ya the best and thanks for using FixYa.


Mar 31, 2010 | 1991 Honda Accord

Not finding what you are looking for?
Cars & Trucks Logo

Related Topics:

26 people viewed this question

Ask a Question

Usually answered in minutes!

Top Mercedes-Benz Experts

Colin Stickland
Colin Stickland

Level 3 Expert

22219 Answers


Level 3 Expert

76630 Answers

Michael Contreras
Michael Contreras

Level 2 Expert

166 Answers

Are you a Mercedes-Benz Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides