AfterMarketNews AfterMarketNews Auto Care Pro AutoCareCareerHub Brake&Frontend BodyShopBusiness Counterman EngineBuilder Fleet Equipment ImportCar Motorcycle & Powersports News Servicio Automotriz Shop Owner Tire Review Tech Shop Tomorrow's Tech Underhood Service Speedville

Air Filter Show & Tell: Seeing Is Believing

Air filters are normal wear items that ­require regular checks and ­replacement. Their role is to trap dirt particles that can cause damage to engine cylinders, walls, pistons and piston rings. In fuel-injected vehicles, the air filter also plays...

Read more...

Searching for 'Black Holes': Job Totals Reveal Missed Selling Opportunities

The concept for Maintenance Chronicle is simple: We ask one shop to record their maintenance sales for a two-week period, and then we see what we learn from the results. This edition of Maintenance Chronicle also proved to be valuable for the shop we...

Read more...

Selling Batteries With a State of Health Strategy

Batteries can be an easy sell in some ways ­because all customers ­understand the basic importance of the battery. Good battery = car starts; bad battery = car doesn’t start. Unfortunately, many customers aren’t in the market for that new battery...

Read more...

Saab: Fuel Sending Unit Replacement

The 2006 Saab 9-3 Sport sedan came in on the hook and the tow truck driver said, “I think it needs a fuel pump.” The gas gauge was reading less than a quarter of a tank and the low fuel warning light wasn’t on, so a quick fuel pressure check was...

Read more...

KIA: Brake Light On, Tachometer And Speedometer Inoperative

Applicable Models: 2001 Kia Optima LX, 2.4L Complaint The customer states the red brake light is illuminated on the instrument cluster. The ­customer also states the tachometer and speedometer intermittently stop working. Cause Confirmed the customer’s...

Read more...

Mazda: Fuel System Servicing Precaution

Applicable Models: 2004-’07 Mazda3 2005-’07 Mazda6 2006-’07 MX-5 vehicles During service/removal of fuel system parts on the above vehicles, the memory of the malfunctions and the long-term fuel trim need to be cleared by either removing the...

Read more...

Using Volumetric Efficiency to Determine the Health of an Engine

Measuring voumetric efficiency can diagnose problems like blocked catalytic converters, bad MAF sensors or vacuum leaks. Glen Beanard show you how to do it with a scan tool. For the complete article, click here.  ...

Read more...

Phoenix Systems Sends Facebook Giveaway Winner to Meet Larry McReynolds for All-Star Race

Phoenix Systems, maker BrakeShot, BrakeStrip and Reverse Brake & Clutch Bleeders, announced the winner of its 2015 Win Race Tickets Facebook Giveaway. Suzanne Cleary Drews from Edgewater, FL, is this year's grand-prize winner. Phoenix Systems will...

Read more...

Intermittent Engine Misfire Analysis

Even for an experienced diagnostic technician, attempting to diagnose an intermittent misfire condition that occurs only under specific driving conditions can be a frustrating exercise. Contributor Gary Goms breaks it down, and includes tips for using...

Read more...

Diagnostic Dilemma: The Case of the Missing Code

When doing mobile diagnostic work, no-code stalling complaints are a major part of your agenda. In most cases, the client shop is simply too busy to duplicate the failure or, in some cases, a long test drive will yield nothing in the way of useful...

Read more...

Secondary Ignition: The Art of Spark

What is a coil? From the beginning of the internal combustion engine, several different ignition systems have been used to create a high-energy spark. The most popular system, and the one that’s in use today, is a step-up coil. A coil is nothing...

Read more...

Diagnosing Catalytic Converter Failure Symptoms

Although construction can vary according to engine application, the common three-way catalytic converter contains a reduction and oxidation stage. To create maximum surface area, each stage is generally a ­ceramic or stainless steel honeycomb substrate...

Read more...

Home Chassis Nivomat Shock Absorbers: Self-Leveling Monotube Ride Control Units

Print Print Email Email

The Nivomat Shock Absorber is a self-leveling monotube shock absorber developed by Sachs. Nivomat is a contraction of two French words, niveau and automatique. When translated to English, it would be level automatic or automatic level.

Nivomat shocks are used by Chrysler, Ford, General Motors, Jaguar, Kia, Mitsubishi, Saab, Volvo and other OEMs. The system is also available on the GM Suburban and Tahoe as part of ZW7 Premium Smooth Ride Suspension. Replacement units are available from Monroe, ZF Sachs and OES suppliers.

The system makes use of the mechanical energy which is generated during the first meters of driving from the relative movement between the axle and vehicle body.

An unlevel vehicle can create many problems. Extra weight on the rear axle shifts the center of gravity, which has a major impact on the ride characteristics. In critical situations, the vehicle can be very difficult to control. Under these conditions a “floaty” ride characteristic can not be considered as comfort anymore.

Other effects are increasing expenses: The tires wear unevenly and faster. Bad aerodynamics causes a higher fuel consumption. Greater strain is also placed on the axle as a whole.

In place of conventional shock absorbers, this unique system is installed on the rear axle. While providing additional roll stability without requiring any additional electronics, the Nivomat adjusts the vehicle to the optimum ride height for every load condition, thus ensuring a safe and comfortable ride.

The Nivomat system does more than just level the vehicle under load. As the load increases, the pressure inside the shock increases as oil is displaced from the reservoir to the inside of the unit, compressing the gas volume. This creates a progressive increase in spring rate and damping with little or no change to ride frequency.

The Nivomat is like an ordinary monotube shock absorber with a hydraulic piston, tube and accumulator.  There are two different configurations of the shock.  The first looks like a conventional twin tube air shock with a dust cover.  What appears as a dust cover houses the high pressure accumulator and low pressure oil reservoir.  

The second configuration has its high pressure accumulator at the top of the shock.  This reduces the overall diameter of the shock.  This allows the shock to be installed in a more confining space, such as an independent rear wheel drive suspension and can be mounted in a shaft up or down configuration as designed by the manufacturer.  The normal application for this shock absorber is for the rear suspension of a passenger car or SUV.  

What gives the shock its leveling capability is a pump mechanism and oil reservoir that can increase the accumulator pressure, which increases the shocks lifting capability. It is used in combination with springs matched to the load capacity of the shock to reduce suspension travel while utilizing more of the piston and shaft travel of the shock.  

This maintains the ride quality whether the vehicle is operated with a driver only or to compensate for passengers and luggage. The big advantage to the Nivomat is the shock absorber requires no plumbing, compressor and height sensing device to level the vehicle.  The normal movement of the suspension over a regular road surface provides enough pumping action to level the vehicle.

Leveling Components:
The accumulator can be a diaphragm or piston.  The normal pressure contained the accumulator ranges from 20 bar (290 psi) to 50 bar (725 psi).  The pump can increase the accumulator pressure from 90 bar (1305 psi to 130 bar (1885 psi).  Under driving conditions, pressure can reach 350 bar (4,424 psi).  

The control sleeve is fixed in the shaft and controls oil flow through the spiral cut and release bore in the pump rod.  The inlet valve is a one way check valve located at the end of the spiral cut in the hollow pump rod.  
The low pressure oil reservoir contains the oil used to charge the pump mechanism.  The pump is located at the end of the control sleeve and uses a pump cup, pump and balance spring.

Leveling Operation:
The Nivomat shaft and piston provide the same damping as a normal monotube shock.  The difference is that the shaft is hollow and contains the pump mechanism.  The pump is operated by the displacement of oil caused by the movement of the shaft in and out of the shock. When the piston shaft moves out of the shock, oil is drawn from the low pressure oil reservoir through the hollow pump rod and inlet valve into the pump chamber.  

Since Nivomat is mechanical, the vehicle needs to be moving before the pump starts to work and it takes about a mile to a mile-and-a-half of travel before the vehicle reaches its optimal level point.

The pump is made up of a pump cup and balance spring.  When the piston shaft moves into the shock, the oil is compressed collapsing the pump spring and expanding the balance spring to fill the pump cup.  When the shaft moves out of the shock, the control sleeve opens the spiral cut in the pump rod, and the oil is forced into the main chamber of the shock. The pump and balance spring return the pump cup to its level position.  This increases the pressure in the accumulator creating more lift to return the piston and shaft to the level position. In the level position, the control sleeve closes the spiral cut and the shock operates normally until the next inlet and pump action.

The release bore is used to return the shock to the level position when the load is removed from the vehicle.  When the shaft and control sleeve is extended out of the shock past the release bore, the oil that was pumped to increase the accumulator pressure and lift is returned to the low pressure reservoir.

Installation:
When replacing a load leveling shock absorber, it is necessary to inspect both mounting points for damage and stress cracks.  All mounting hardware should also be replaced.  All fasteners should be tightened to their proper torque specifications. 

The diameter of a conventional shock absorber is 54 mm (2-1/8-in).  The diameter of a Nivomat shock can range from 60 mm (2-5/8 in) to 72 mm (2-7/8 in).  Make sure the shock is properly mounted to provide adequate clearance.  It is recommended to test the operation of the shocks by loading and driving the vehicle.

Disposal
Take the following steps, making sure to comply with local safety and environmental protection regulations to recover and dispose of the oil before scrapping the shock.

Diaphragm Type (Except Mercedes Benz M Class)
1. Clamp the shock in a horizontal position using a vice with the shaft fully extended.
2. Center punch a mark 50 mm (2 in) from the top of the tube.
3. Drill a 5 mm (3/16 in) hole to exhaust the gas and oil from the low pressure reservoir.
4. Center punch a mark 25 mm (1 in) from the bottom of the shock’s tube.
5. Drill a 5mm (3/16 in) hole to exhaust the gas from the high pressure accumulator.
6. Remove the remaining oil in the shock by pumping the shaft in and out of the tube.
7. The shock can now be scraped.

Piston Type (Mercedes Benz M Class)
1. Clamp the shock in a horizontal position using a vice with the shaft fully extended.
2. Center punch a mark 50 mm (2 in) from the bottom of the tube.
3. Drill a 5 mm (3/16  in) hole to exhaust the gas and oil from the low pressure reservoir.
4. Center punch a mark 10mm (3/8in) from the top of the tube.
5. Drill a 5 mm (3/16 in) hole to exhaust the gas from the high pressure accumulator.
6. Remove the remaining oil by pumping the shaft in and out of the tube.
7. The shock can now be scraped. 

The following two tabs change content below.

Gene Markel

Latest posts by Gene Markel (see all)

Latest articles from our other sites:

Saab: Fuel Sending Unit Replacement

The 2006 Saab 9-3 Sport sedan came in on the hook and the tow truck driver said, “I think it needs a fuel pump.” The gas gauge was reading less than a quarter of a tank and the low fuel warning light...More

New Study Reveals When, Where And How Much Motorists Drive

On average, Americans drive 29.2 miles per day, making two trips with an average total duration of 46 minutes. This is according to a new study currently underway by the AAA Foundation for Traffic Safety...More

Saab: Fuel Sending Unit Replacement

The 2006 Saab 9-3 Sport sedan came in on the hook and the tow truck driver said, “I think it needs a fuel pump.” The gas gauge was reading less than a quarter of a tank and the low fuel warning light...More

Lithium: An Element That Is Charging Ahead

What is an EMV? As you read the hybrid and plug-in articles that my company, ACDC, is writing this year, we have coined a new term: EMV (electric motor vehicle). Rather than use hybrid, plug-in hybrid,...More

Snap-on Introduces New Software Upgrade 15.2

Keeping a technician’s diagnostic tool up-to-date is the only way a shop can ensure that they have the latest codes, tests, tips and data out of the box and miles down the road. With the new Snap-on...More

New CHARGE IT! PP15 POWER PAC Power Supply and 12V Jump Starter

Clore Automotive introduces CHARGE IT! Model PP15, a 15,000-mAh lithium-battery based multi-voltage power supply and 12-volt jump starter. With 15,000 mAh of reserve capacity and multiple output voltages,...More

Ultimate Underhood: Chrysler Slant Six

While the Chrysler Slant Six did not have the raw power of the Hemi, it was just a sophisticated. The Slant Six went into production in 1960 and lasted until 1983. The 30º tilt was borrowed from Mercedes-Benz...More

Lithium: An Element That Is Charging Ahead

What is an EMV? As you read the hybrid and plug-in articles that my company, ACDC, is writing this year, we have coined a new term: EMV (electric motor vehicle). Rather than use hybrid, plug-in hybrid,...More