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Production Changes - Evolution Throughout Production - Air suspension

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Anti-Freeze Device

There are three different versions of the anti-freeze device. Versions 2 and 3 are directly interchangeable. Version 1 can be replaced with the later versions, however there are a few other small parts that are then no longer used.

All three versions attach to the mounting bracket the same way. The major difference between the first version and the two latter versions is that the first version drew in fresh air from the engine's air cleaner. The later two versions had their own air cleaner. The first version requires that the top to the engine's air cleaner housing have the nipple on it to accept the rubber hose.

Notice that Version 1 has three pressed-in pipe fittings for the air line connections. Version 2 and 3 have the small cylindrical air cleaner screwed into the side adjacent to the radiator. Version 2 retains the pressed-in pipe fittings for the other two air line connections. Version 3 has screw-in fittings for the other two air line connections. Version 3 also has a capped connection point for a fourth air line. No 300SE uses this fourth connection point.

1st Version. Used on sedans until chassis end number 004374 and coupes & convertibles until chassis end number 004378.

2nd Version. Used on all cars after the chassis end numbers listed in the Version 1 section.

3rd Version. There is no clear indication as to exactly when Version 3 replaced Version 2 other than most '64 cars had Version 2 and '65 cars had Version 3.

Air Supply Reservoir

There are three different versions of the air reservoir.

Version 1: Mercedes # 112-320-08-52. Tank capacity is not known.

Version 2: Mercedes # 112-320-10-52. This is a 9.0 liter tank.

Version 3: Mercedes # 109-320-00-52. This is a 7.5 liter tank.

Version 1 was installed on all sedans until chassis end number 004208, except for 004169, 004181, and 004193. Version 1 was installed on all coupes and convertibles until chassis end number 004171. The only clear distinction between Version 1 and Version 2 is that the screw plugs at the top of the tank are different sizes, and, therefore, the O-ring seals are also different sizes. Version 2 and Version 3 both use the same size plug and O-ring seal. There is no clear indication when Version 3 replaced Version 2, other than that Version 2 was used on cars up through at least 006741.

There are changes in most of the steel air lines through-out the car. It is not clear what the changes were.

There were two different versions of Dunlop front calipers. I can find no information to indicate exactly what the differences were, but it appears that the difference is in the wheel cylinder(s). The factory parts book, Edition D indicates that there were two different types of brake pads for the Dunlop front calipers. I can't say for sure, but it seems reasonable to assume that one type of pads is for the early version of caliper, and the other type pads were for the later version of the caliper.

One indication of the time frame in which the change in the caliper occurred is the fact that the change isn't mentioned until the Edition D version of the parts book, after the changeover to the Teves (ATE) calipers. This may mean that the later style of Dunlop caliper was never actually used in production, but was used solely as a replacement part for repairs. I mention this to help address the unlikely situation where an owner buys a new pair of pads for his/her car but the pads don't fit correctly.

Dunlop brake calipers (of either version) where installed on the front brakes of the 300SEs through VIN number after which Teves (ATE) calipers where installed.

The information on the rear axle calipers is a bit less clear. Judging from the information in the factory parts books, Dunlop Calipers were used throughout production, though there were three different versions.

Version 1 was used up through VIN # 006975.

Version 2 was used from VIN # 006976 through 008288.

Version 3 was used from VIN # 008289 to the end of production. (See End of Life/Break in Production)

The caliper version #1's part number is superseded by caliper version #3's part number but also requires replacing the steel brake fluid lines to the calipers.

The caliper version #2's part number is also superseded by caliper version #3's part number but also requires a different set of brake pads. Interestingly enough, the pads are indicated to be those used for the front brakes with Teves (ATE) calipers. This almost has to be an error in the part number in the book. It doesn't make any sense to change to the later style caliper but not use the same pads as would have been used when the later style caliper was installed during production. There were no changes to the rotor anywhere during production.

Model Changes:
In January 1964 the engine incorporated several substantial changes. The changes were so substantial that the engine's type designation was changed. The sedan engine's designation changed from 189.984 to 189.986. The coupe and convertible engine's designation changed from 189.985 to 189.987.

For reference purposes, the engine underwent some minor additional changes in August 1965 for use in the new square back sedans which replaced the finback sedans. The 108 chassis 300SE (no air suspension) used the 189.989 engine, and the 109 chassis 300SEL used the 189.988 engine.

It is worth noting that the only difference between the sedan engines (189.984 and 189.986) and the coupe/convertible engines (189.985 and 189.987) is that the coupe/convertible engines were outfitted with a drive for the mechanical tachometer.

The major differences between the 189.984/189.985 engines and the 189.986/189.987 engines are an increase in compression, changes in manifolds, and replacement of the two-plunger injection pump with a six-plunger injection pump. However, there are numerous, less conspicuous, differences.

Almost all of the engine's internal parts are different. See the section on the engine's individual components for more information. Note that even though the cylinder heads are mechanically interchangeable between the early engines and late engines, this should not be done because the early engines do not have as many water passageways.

Air Cleaner:
The air cleaner assembly changed at the same time that the engine changed from 189.984/985 to 189.986/987 though the two assemblies are interchangeable. The later air cleaner canister has a special shape to allow incoming air to better circulate around the filter element.

Additionally, there was an extension for the air inlet. This extension fits on the existing air cleaner assembly and moves the air intake further out into the air stream in front of the radiator. This extension was supplied on all 189.986/987 engines, and on the 189.984/985 engines from chassis:



At the same time as this change, the air cleaner cover also lost it's nipple for the air line to the air suspension system's anti-freeze device.

There was some additional mounting hardware for the assembly available for "export" vehicles, upon "special request". We have never seen a vehicle with the additional hardware, and don't know what its purpose was. This hardware consisted of: 2 ea. 8x25mm hex head screws, 1 ea. 8x20mm hex head screw, and 3 ea. 8,4 DIN 125 washers.

Since 300SEs were originally available only with an automatic transmission, all mixture controllers were outfitted with the electric switch (this switch is one of two that actuate the double acting solenoid on top of the automatic transmission). Only after the introduction of the optional manual transmission in 1963 did the parts become available to eliminate the switch assembly on the mixture controller.

All of the mixture controller part numbers listed  below include the switch. If a new mixture controller was ordered for a manual transmission engine, then the special parts that eliminate the switch also have to be ordered, or taken from the old unit.

000 140 17 53   1st version  189.984/985 engines.
Replaced by 2nd version. Reason for, and time of,  replacement is unknown.

000 140 18 53   2nd version  189.984/985 engines.
Used on 189.984-12 engines up to engine 003717 and on 189.985-12 engines up to 000701.

000 140 03 07   3rd version 189.984/985 engines.
Used on 189.984-12 engines as of  003718 and on 189.985-12 engines as of 000702.

000 140 29 53   4th version 189.986/987 engines.
Used on all 189.986/987 engines. Replaced by 5th version. Reason for, and time of,  replacement is unknown.

000 140 41 53   5th version 189.986/987 engines.
Used on 189.987-10  engines up to 000678 and on 189.987-12 engines up to 001434.

000 140 46 53   6th version 189.987/988/989 engines.
Used on 189.987-10  engines as of 000679 and on 189.987-12 engines as of 001435. Also used on all 189.988/989 engines.

The 189.984/189.985 engine's camshaft and bearings underwent some lubrication changes. Both style camshafts are hollow and are pressure fed oil from the rear cam bearing, but the early style camshaft has holes drilled on the backside of each cam lobe to lubricate the rocker arms. The later style camshaft does not have the holes on the backside of the lobes. Instead, there is an oil pipe that runs the length of the camshaft and is screwed to each of the cam bearings. The pipe is supplied with oil from the top of the fourth cam bearing, and has holes drilled in it over top of each cam lobe. This provides a better supply of oil to each lobe.

The early style cam can be replaced with a later style cam (still from a 189.984/189.985 engine) so long as the bearings, oil pipe, and other related hardware are also changed at the same time.

The last engines with the early style cam are:





Engines with serial numbers higher than these should have the later camshaft and bearings.

All 189.986/987/988/989 engines used the same camshaft and bearings, but not the same as either type 189.984/985 camshaft and bearings.

It should be noted that the factory did have undersize camshaft bearings available in both 0.10 mm and 0.25 mm undersize for all three versions of bearings.


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