Sullair 185 Review | Tow Behind Air Compressor

Sullair 185 is a portable rotary screw air compressor, that meets emission requirements, producing just 185 cfm at 100 psi.

Despite being superior, the unit is designed to offer the same durability, maneuverability, and simple serviceability the brand is known for.
The diesel air compressor is also compliant with the US EPA sound requirements of 76 dBA at 7 meters. This guarantees you a clean and quiet operation.

The air compressor comes in multiple engine options to meet different requirements. 

It features a more efficient direct-driven air end, two-stage dry type air filters, a Dual fuel titration system, and adjustable-height hitch. As proof of quality, the manufacturer offers a one-year standard warranty on the product.

It is also backed by a 2-year standard air end warranty. Throughout this Sullair 185 T4F Review, you will learn what makes the unit stand out from other air compressors.

Engine Option Fuel Consumption (at Full Load)Cooling System CapacityMax Power Rating
CAT C2.2 (T4F)2.9 GPH2.6 gal 41.6 HP
Perkins 404F-E22T2.9 GPH2.6 gal 48.8 HP
Kubota KUB1803 (T4F)2.7 GPH2.75 gal 49 HP 

Sullair 185 Air Compressor Benefits 

  • Offers easy access to engine parts, making the air compressor relatively easy to service and maintain 
  • Comes in multiple engine options including CAT, Kubota, and Perkins Engines with turbo-charged options for high-altitude areas
  • Comes with Sullair 185 standard fill of the AWF all-weather lubricant to keep the air compressor running efficiently, even in extreme weather conditions
  • Features a compact design for improved maneuverability, and high-quality construction for enhanced durability 
  • Equipped with the improved Sullair 14-series air end that features an integrated leak-free direct-drive design

Why Choose the Sullair 185 T4F Air Compressor? 

Sullair has been one of the best air compressor manufacturers for more than 50 years now. As a matter of fact, they are one of the very first manufacturers to produce rotary screw air compressors in the industry.

Their products are renowned across the globe for their legendary durability. The 185 series is one of the most sought after air compressor models by this manufacturer.

Just like the other Sullair models, the new 185 T4F offers exceptional durability, reliability, and performance as illustrated below.


Although primarily designed to meet emissions and noise requirements, the Sullair 185 air compressor does not compromise on quality. It is fitted with a corrosion-resistant enclosure, with stainless steel latches and hinges. 

The Sullair 184 T4F construction also includes galvanized sheet metal with composite fenders and caps. These, in addition to the renowned air end design, are meant to make the model more durable.

As such, the air compressor can withstand years of use in the most demanding conditions. 


Customers who have already tried the Sullair 185 tier 4 final emissions-compliant unit find it very reliable on various applications, ranging from construction to mining sites.

To show you just how confident they are with their product, the product is offering extended period warranties on the 185 T4F air compressor model. 

Superior Performance

For decades now, Sullair has been working tirelessly on innovations that ensure you get the very best from your air compressor. The Sullair 185 portable air compressor is engineered with features that will help you optimize your business potential.  

The compact design of the air compressor makes it easier to maneuver and store after use.

You will also find this model to be efficient on fuel—if you can run continually for more than 10 hours on a tankful of fuel. Again, the unit has been proven to be powerful and consistent in an array of working conditions. 

Top Features and Capabilities 

The Sullair 185 T4F is one of the best rotary screw air compressors you can buy today. Not only is it powerful, efficient, and reliable, it is also compliant with US  emissions requirements.

It features quality construction, right from the outer clamshell to the inner components. 

In addition to being compact and lightweight, the air compressor has an adjustable height hitch, recessed taillights, and an independent rubber torsion suspension system.

These make the air compressor easy to toe behind a vehicle and to move about at the job site. The product also boasts of a myriad of performance and convenience features, including: 

Highway-Towable Gear 

Having been designed to be a powerful, heavy-duty air compressor model, the Sullair 185 is quite heavy. To allow for easier movement of the equipment from one point to another, it is fitted with a pair of wheels and highway Towable gear. 

The product features an adjustable height hitch, with a screw jack pad and a 3” square drawbar.

The wheels are fitted with independent rubber torsion suspension systems. Since the air compressor is meant to be towed behind a vehicle, it comes complete with a rear bumper with integrated recessed taillights.

For easy lubrication, the axle wheel bearings on this unit are fitted with grease fittings. The hitch is equipped with security chains to secure the air compressor in place as you tow it behind your vehicle. 

Capacity Control System 

This is a system that is specifically designed to control air intake amounts in the Sullair 185, matching it to the prevailing output requirements on the compressor.

It comprises of an air inlet valve, pressure-regulating valve(s), engine speed control, and the associated tubing.

The functioning of the capacity Control system of this model may be described in four distinct phases of operation, including: 

Start Phase (0-40 psig) 

This phase kicks in whenever the air compressor is started. At this point, the sump pressure quickly rises from 0 to about 40 psig/2.8 bar.

The pressure regulator valve is usually inactive throughout this phase. The idle warm-up control keeps the inlet valve closed for engine idle operation within this pressure range. 

After running the air compressor for 30 seconds, the instrument panel annunciator light will go off, at which point you need to engage the warm-up selector valve.

To do this, you should turn the handle of this valve  from Start to the Run position. At this point, the inlet valve is fully open due to the accumulated pressure, allowing the air compressor to operate at its optimal capacity.

Since the air compressor is functioning at its capacity, the engine will also run at its full speed.

Normal Operation (80-100 psig) 

As soon as you turn the warm-up control selector valve handle to Run, the sump pressure will quickly rise to 80 psig/5.6 bar.

During this period, the inlet valve remains fully open to allow for maximum air output. The engine will continue to run at full speed during this phase of operation.

Modulation (100-110 psig) 

If the demand on the compressor happens to be less than its rated capacity, the service line pressure rises above the 100 psig/6.9 bar mark.

This prompts the pressure regulating valve to open gradually, applying pressure to the inlet valve piston and engine speed control. This alone will close the inlet valve partially, hence reduce engine speed. 

As the pressure builds up, the inlet valve piston will continue to close the inlet valve gradually until engine speed reaches the preset idle speed.

If air demand on your Sullair 185 T4F compressor increases, the sump pressure will fall below 110 psi. This causes the pressure regulating valve to close.

The air inlet valve will now open fully, and the engine will run faster in an effort to reach its preset full-load rating.

There is a small orifice between the inlet valve and the pressure regulating valve.

This orifice vents out a small air amount whenever the pressure regulating valve is open or discharge any moisture accumulated in the regulator. 

Sullair 185 series air compressors


Normally, the blowdown valve in the Sullair 185 air compressor remains closed during operation.

If the air compressor is switched off, the backpressure in the compressor inlet will cause the blowdown valve to open automatically. This action vents the sump pressure out of the air compressor. 

Environmental Features 

As mentioned earlier, Sullair 185 series air compressors produce fewer emissions, hence they are more friendly to the environment.

All the engine options used in this model are Tier 4 emissions compliant. With the 185 T4F air compressor model, compressor lube change will only be required after about 1500 hours of operation. 

The engine oils, on the other hand, should be changed after 500 hours of operation.

This reduces the rate at which you will be disposing of those harmful materials to the environment. Again, the air compressor is fitted with a sealed crankcase ventilation system. 

Quality Construction 

Extended durability is one of the key selling points of Sullair 185 series air compressors.

This is made possible by the high-quality materials and components used to make them. The US manufactured air compressors are made of galvanneal sheet metal. 

The Unit is equipped with composite fenders and caps, an aluminum instrument panel door as well as stainless steel hinges and latches.

The product also has a number of plated fittings and hardware components for enhanced durability.

Sullair 185 series air compressors 4

Intuitive Instrument Panel and Controls 

The Sullair 185 tier 4 final emissions-compliant air compressor instrument panel is equipped with a myriad of controls, indicators, and switches.

To operate these controls, you first need to energize the electrical system by turning the air compressor ignition On. 

The Ignition switch is just one of the many switches and controls you will find in this control panel. These are other important controls located in the Sullair 185 air compressor control panel:

Hour Meter

This meter is used to accurately keep track of the working hours of the air compressor.

It automatically records the number of hours the unit has been operational since when it was new. This will come in handy when you are planning and logging service schedules.

Cold Weather Starting Aid 

This is a button that you need to use while starting your air compressor in the cold weather.

In this regard, you need to start this button before starting the compressor. Pressing the cold weather starting aid button will pre-heat the engine, making it easier to start even in freezing conditions. 

Sullair 185 T4F Portable Air Compressor Review

Discharge Temperature Switch 

This is a switch that scheduled to initiate an automated shutdown of the air compressor when the discharge Temperature reaches a certain value.

If the threshold discharge temperature is reached, this switch will trip to open the electrical circuit. 

Fluid-Level Sight Glass 

Indicates the fluid level in the receiver tank. The proper level is marked halfway up the transparent sight glass. For accurate results, you should only check the level when the compressor is shut down and on level ground.

Idle Warm-Up Control 

Keeps the compressor inlet valve closed for reduced compressor load at start-up.

When the compressor is warmed-up, the handle should be turned from the START to the RUN position for full operation.

Air Pressure Gauge 

This is a gauge that continually monitors the pressure inside the receiver tank. It shows the current pressure in the tank, whether on a load or unloads condition. 

Thermal Valve 

This valve serves as a temperature regulator. It functions by directing the compressor fluid to the cooler or the compressor unit depending on the current temperature. 

Air Inlet Valve 

Regulated the amount of air allows entering into the air compressor through the inlet opening. The inlet valve is triggered to open or close by signals from the air pressure regulator(s) depending on the demand for compressed air.

Pressure Relief Valve 

Vents sump pressure to the atmosphere, if the pressure inside the sump exceeds 200 psi (13.8 bar).

Pressure Regulator 

Allows the pressure signal to reach the engine speed control and the air inlet valve to control air delivery according to demand.

Pressure Relief Valve 

Compressor Shutdown and Warning System

Unlike some of the leading air compressor models in the market, the 185 T4F has a The Shutdown System and Annunciator Module (SSAM).

This module is meant to continually monitors the compressor for various conditions that require it to shutdown. 

If a shutdown condition is detected, SSAM will shut down the compressor and display (flashing) the appropriate code on the instrument panel annunciator light. The display will continue flashing until the ignition switch is turned OFF. 

Startup Logic Functionality 

The SSAM module also harbors the startup Logic following an automated air compressor shutdown.

With the ignition switch in the On position, SSAM will illuminate the appropriate diagnostic light for 30 seconds. If you press the ignition switch within these 30 seconds, the system will automatically engage the starter. 

The low engine speed switch is inactive during this startup time interval. By the end of these 30 seconds, the annunciator light goes out and the engine START cycle is disabled.

If this happens, the system will automatically run all the necessary checks, including a low-fuel level(for installed models). 

Final Verdict 

The Sullair 185 T4F package includes a diesel engine, a heavy-duty rotary screw compressor, a compressor inlet system, a diesel tank, a compressor discharge system, cooling, and lubrication system.

Each compressor also features capacity control and a comprehensive instrument control panel. Owing to such features and capabilities, 185 series compressors are known to deliver unmatched reliability and performance.

Although the model does not come cheap, the Sullair 185 tier 4 final emissions-compliant air compressor is worth every penny.  

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