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Rexroth High Pressure Oil Seal Selection Guide: Prevent Leakage and Repeat Repairs


Learn how to select the correct Rexroth high pressure oil seal, prevent hydraulic pump leakage and reduce repeat repairs and equipment downtime.

A hydraulic pump may cost thousands of dollars, but one incorrectly selected shaft seal can cause oil leakage, contamination, repeat repairs and unexpected equipment downtime.

For hydraulic pump repair companies, hydraulic motor rebuilders, construction machinery parts distributors and industrial maintenance teams, the biggest challenge is not simply finding an oil seal. It is finding the correct Rexroth high pressure oil seal for the exact pump or motor model.

Two seals may look similar and even share the same inner and outer diameters. However, differences in seal structure, width, material and installation position can completely change their performance.

This guide explains how to select the correct hydraulic pump oil seal and avoid the most common causes of premature leakage.

Why New Hydraulic Pump Seals Fail

When a newly installed oil seal starts leaking, many buyers immediately blame the seal quality.

In reality, early failure may also be caused by:

  • Incorrect seal size

  • Wrong sealing lip structure

  • Incorrect installation direction

  • Worn shaft surfaces

  • Excessive case pressure

  • Restricted drain lines

  • Installation damage

  • Incorrect material selection

  • Shaft runout or bearing play

  • Contaminated hydraulic oil

Replacing the seal without finding the root cause may only provide a temporary solution.

A reliable repair requires the correct oil seal, proper shaft inspection, hydraulic system diagnosis and controlled installation.

Do Not Select a Rexroth Pump Seal by Size Alone

Many inquiries contain only three dimensions:

We need a 50 × 72 × 7 oil seal.

This information is not always sufficient.

A complete hydraulic pump seal specification should include:

  • Pump or motor brand

  • Complete model number

  • Series and displacement

  • Inner diameter

  • Outer diameter

  • Complete width

  • Seal structure

  • Material

  • Equipment application

  • Operating conditions

For example, the MEIOU HPS cross-reference lists a 50 × 72 × 7/5 BAFSL1SF VITON seal for several A2FO and A2FE applications.

However, this does not mean every standard 50 × 72 oil seal is suitable.

The complete width and seal structure must also be verified.

Always Confirm the Complete Pump Model

“Rexroth pump seal” is not a complete purchasing description.

Rexroth hydraulic equipment includes many series, such as:

  • A2FO fixed pumps

  • A2FE plug-in motors

  • A2FM fixed motors

  • A4VG variable pumps

  • A4VSO variable pumps

  • A6VM variable motors

  • A7VO variable pumps

  • A10V piston pumps

  • A10VG variable pumps

  • A11V piston pumps

Different displacements within the same series may use different shaft seal sizes.

For example, smaller A2FO models use a 28 × 40 × 6/5.5 seal, while larger models use specifications such as 35 × 52 × 6/5.5, 45 × 62 × 7 and 60 × 80 × 7/5.5.

A better inquiry is:

High pressure shaft seal required for Rexroth A2FO45 hydraulic pump. Please confirm the correct size, structure and material.

Providing the complete model helps prevent quotation errors and incorrect shipments.

Why Seal Structure Matters

The MEIOU HPS cross-reference includes several oil seal structures, such as:

  • BAFSL1SF

  • BABSL10FX2

  • BAB2SL05

  • BAFSL1F

  • BAFSLSF

  • BAB3SI

These codes represent different sealing structures and should not be ignored.

A general-purpose rotary shaft seal may fit into the housing but still fail under hydraulic pump operating conditions.

Hydraulic pump shaft seals may face:

  • Continuous rotation

  • High oil temperature

  • Pressure fluctuations

  • Shaft vibration

  • Long operating cycles

  • Contaminated environments

For example, the A4VG series uses different dimensions and both BAFSL1SF and BABSL10FX2 seal structures depending on the pump model.

Buyers should therefore match the pump model, dimensions, structure and material, not dimensions alone.

Do Not Ignore Double Width Specifications

Some high pressure oil seals use sizes such as:

  • 35 × 52 × 6/5.5

  • 50 × 72 × 7/5

  • 60 × 80 × 7/5.5

The second width figure is not necessarily a printing error.

It may relate to the seal profile, lip-side structure or installation position.

Replacing a 50 × 72 × 7/5 seal with an ordinary 50 × 72 × 7 oil seal may cause:

  • Incorrect installation depth

  • Insufficient support

  • Lip contact with a worn shaft area

  • Seal deformation

  • Premature leakage

Always record every dimension of the removed seal exactly. Do not round the measurements before confirming the original structure.

Is VITON Always the Correct Material?

Most hydraulic pump and motor seals in the cross-reference are listed in VITON.

VITON is commonly used in demanding hydraulic applications because of its resistance to heat and many industrial oils.

However, material selection should also consider:

  • Hydraulic oil type

  • Continuous temperature

  • Peak temperature

  • Shaft speed

  • Equipment duty cycle

  • Pressure fluctuations

  • Working environment

The catalogue also includes NBR seals for certain motor applications, confirming that not every hydraulic system requires the same material.

A high-grade material cannot compensate for the wrong structure, damaged shaft or excessive case pressure.

Inspect the Shaft Before Installing a New Seal

A new hydraulic pump oil seal cannot seal reliably against a damaged shaft.

Before installation, inspect the shaft for:

  • Wear grooves

  • Scratches

  • Rust

  • Pitting

  • Burrs

  • Excessive runout

  • Bearing play

  • Misalignment

A worn groove may prevent the sealing lip from maintaining uniform contact.

In this situation, replacing the oil seal alone may not solve the leakage problem. The repair may require shaft restoration, replacement, a suitable repair sleeve or adjustment of the installation position.

Check Case Pressure and Drain Lines

When a new shaft seal is pushed out, deformed or starts leaking immediately, excessive case pressure may be the real cause.

Possible causes include:

  • Blocked case-drain lines

  • Restricted filters

  • Undersized drain hoses

  • Incorrect hose routing

  • High oil viscosity during cold start

  • Excessive internal pump wear

  • Pressure spikes

A stronger seal may delay failure, but it cannot permanently correct an abnormal hydraulic system.

Before replacing the seal again, inspect the drain circuit and measure the actual case pressure where possible.

Hydraulic Pump Oil Seal Installation Checklist

Before installation:

  • Confirm the complete pump model

  • Verify the seal dimensions

  • Check the seal structure

  • Confirm the material

  • Inspect the shaft and housing

During installation:

  • Clean the housing completely

  • Protect the lip from splines and sharp edges

  • Apply compatible lubrication

  • Press the seal evenly

  • Confirm the installation direction

  • Maintain the correct installation depth

After installation:

  • Rotate the shaft manually

  • Check for abnormal resistance

  • Inspect the case-drain line

  • Test the unit at controlled speed

  • Monitor leakage and oil temperature

A few minutes of inspection can prevent hours of repeated repair work.

What Information Should Buyers Send?

To receive an accurate quotation, send the supplier:

  • Pump or motor brand

  • Complete model number

  • Old seal dimensions

  • Seal type or marking

  • Photos of both sides

  • Shaft diameter

  • Housing bore size

  • Required quantity

  • Equipment application

  • Leakage symptoms

  • Delivery country

A clear inquiry may look like this:

We need a high pressure shaft seal for a Rexroth A4VG hydraulic pump. Please confirm the correct seal according to the complete pump model. Old seal photos and measurements are attached.

For A4VG pumps, the seal dimensions change according to the displacement, so the full model number is essential.

Final Advice

Selecting a Rexroth high pressure oil seal is not simply a matter of finding a similar-looking product.

A reliable process should follow this order:

Confirm the pump model → verify the dimensions → match the structure → confirm the material → inspect the shaft → check case pressure → install correctly

Skipping one step may turn a small oil seal replacement into an expensive repeat repair.

Save this guide for your next hydraulic pump maintenance project.

Need help identifying a Rexroth pump or motor seal? Send us the complete model, old seal dimensions, clear photos and required quantity.

Comment with the hydraulic pump model you are repairing, save this article for future reference and contact us for model matching, wholesale purchasing and custom high pressure oil seal solutions.

 
 
 
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