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Air suspension for Merc O305

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Air suspension for Merc O305

Postby Littledragon » Mon May 25, 2015 4:26 pm

Hi there everyone,

This is my first post, so please be kind :)

We have bought a 1979 Merc O305 which we are converting to a motorhome. Due to the fact that when the bus is turned off, the left hand side airbags deflate for ease of access to the door, our bus is on a permanent lean whilst we're fitting it out. Does anyone know if it's possible to disconnect this so they stay inflated all of the time or in fact, is this even advisable? I'm really grateful for any information that anyone has.

For anyone interested in the old Mercs, I found this information about my particular girl on a search facility:
ex 0516 AO, ex 0516 AO, Hawkesford's International, Enfield, NSW, ex (2242) m/o 2242, State Transit Authority (STA), Sydney, NSW (B43D).

Does this mean anything to anyone? We are in Melbourne now so it looks like she's come down from NSW at some point.

Cheers,
Tracie
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Re: Air suspension for Merc O305

Postby The Phonj » Mon May 25, 2015 8:11 pm

It may be that one or more of your airbags need replacement. Can you hear any air leaks when you are starting the bus up and trying to build up air; or after shutting it down?
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Re: Air suspension for Merc O305

Postby mrobsessed » Sat May 30, 2015 9:51 pm

I suggest getting some jack stands and placing them under the skid bars of the bus. Being a Mark II, I can't remember if they have any.
If not, be careful where you put them because of the monocoque construction. You don't want to bend anything. Leaks can come from any part of the system from the 4way valve to the levelling valves to (as the Phonj said above) the air bags themselves.
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Re: Air suspension for Merc O305

Postby DiAmOnD T » Sun May 31, 2015 9:13 pm

there is points under the body you can support it from, behind the front and rear axles about 8 inches in from the side panels you will see a small round disc which is mounted on the joint of three or so sections of frame. Sorry its hard to explain without any photos to help.

Echoing above, leaks could be in several different points so its worth spending some time under it with soapy water to find them. there is also one way valves which can leak back (you wont be able to hear these but if there are no obvious external leaks then this will be why)

If you want it to stay inflated while working on it without running the engine there is an air supply point under the front about midway between centre of the bus and the left corner (Look under the bumper bar, you should find it ok) then you can plug a compressor into it to keep constant pressure up

Hope that helps, keep asking away
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Re: Air suspension for Merc O305

Postby 404wanderer » Mon Jun 01, 2015 8:09 pm

Hi, I have an O305 as well. That's really useful information about the external air point. What pressure would you keep it topped up to if I wanted to keep the doors operational. Is there any way of doing that without inflating the airbags? Is it best to keep the airbags under pressure or flat?
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Re: Air suspension for Merc O305

Postby The Phonj » Mon Jun 01, 2015 8:21 pm

8 bar is the normal air operating pressure in a Mercedes O305 - however applying the pressure to the external air point will apply air pressure to the whole air system - brakes, air bags, doors (and anything else that runs off air).
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Re: Air suspension for Merc O305

Postby DiAmOnD T » Fri Jun 05, 2015 10:05 am

Basically you have four air circuits,
1. Front Brakes
2. Rear Brakes
3. Park Brake
4. Auxiliary (Air bags, doors and any other aftermarket/body specific options)

So short answer is no you can't have only air to the doors without filling the air bags (Unless you block a few hoses off)

System pressure is 8 bar but the Aux tank will start filling from 5.5 bar AFTER the other tanks have started to fill

The other option you have is supplying air directly to the auxiliary air tank if you need
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Re: Air suspension for Merc O305

Postby amazon196969 » Sun Feb 11, 2018 3:57 pm

Hi Tracie,
Did you find a fix??I also have a 1979 O305 with left side suspension issue (mine doesn't inflate)...I've been advised it could be a leak or blockage or the self leveling valve is at fault...I have a little mechanical knowledge but haven't ever dealt with air systems.
I have googled my head off to get a better idea of what and where to look for the self leveling valve before i grovel around under my bus (it's a bit wet ATM so I have been putting it off!!!), but have come up with very little.
Also wondering how I find out if mine is a monocoque construction??

cheers
Kylie

Littledragon wrote:Hi there everyone,

This is my first post, so please be kind :)

We have bought a 1979 Merc O305 which we are converting to a motorhome. Due to the fact that when the bus is turned off, the left hand side airbags deflate for ease of access to the door, our bus is on a permanent lean whilst we're fitting it out. Does anyone know if it's possible to disconnect this so they stay inflated all of the time or in fact, is this even advisable? I'm really grateful for any information that anyone has.

For anyone interested in the old Mercs, I found this information about my particular girl on a search facility:
ex 0516 AO, ex 0516 AO, Hawkesford's International, Enfield, NSW, ex (2242) m/o 2242, State Transit Authority (STA), Sydney, NSW (B43D).

Does this mean anything to anyone? We are in Melbourne now so it looks like she's come down from NSW at some point.

Cheers,
Tracie
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Re: Air suspension for Merc O305

Postby LB608 » Mon Feb 12, 2018 6:06 pm

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Re: Air suspension for Merc O305

Postby PoweredByCNG » Wed Feb 14, 2018 12:44 pm

amazon196969 wrote:Hi Tracie,
Did you find a fix??I also have a 1979 O305 with left side suspension issue (mine doesn't inflate)...I've been advised it could be a leak or blockage or the self leveling valve is at fault...I have a little mechanical knowledge but haven't ever dealt with air systems.
I have googled my head off to get a better idea of what and where to look for the self leveling valve before i grovel around under my bus (it's a bit wet ATM so I have been putting it off!!!), but have come up with very little.
Also wondering how I find out if mine is a monocoque construction??

cheers
Kylie


Sounds like the nearside-rear level control valve is faulty in some way (possibly sticking). You can obtain these from a good parts supplier such as Multispares, SMS Diesel or Whites Diesels. When enquiring, provide the VIN number of your vehicle to assist with pinpointing the correct parts.
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Re: Air suspension for Merc O305

Postby Guy_Arab » Wed Feb 14, 2018 7:31 pm

PoweredByCNG wrote:
amazon196969 wrote:Hi Tracie,
Did you find a fix??I also have a 1979 O305 with left side suspension issue (mine doesn't inflate)...I've been advised it could be a leak or blockage or the self leveling valve is at fault...I have a little mechanical knowledge but haven't ever dealt with air systems.
I have googled my head off to get a better idea of what and where to look for the self leveling valve before i grovel around under my bus (it's a bit wet ATM so I have been putting it off!!!), but have come up with very little.
Also wondering how I find out if mine is a monocoque construction??

cheers
Kylie


Sounds like the nearside-rear level control valve is faulty in some way (possibly sticking). You can obtain these from a good parts supplier such as Multispares, SMS Diesel or Whites Diesels. When enquiring, provide the VIN number of your vehicle to assist with pinpointing the correct parts.


SOUNDS LIKE ONE OF TWO PROBLEMS AIR BAGS NOT SEALING OR YOU HAVE A FAULT FOUR WAY VALVE
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Re: Air suspension for Merc O305

Postby PoweredByCNG » Wed Feb 14, 2018 7:49 pm

Guy_Arab wrote:...OR YOU HAVE A FAULT FOUR WAY VALVE


Can you please stop posting in CAPS?

Four way valve should only be suspected IF one or more air tanks don't fill.
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Re: Air suspension for Merc O305

Postby Guy_Arab » Wed Feb 14, 2018 8:47 pm

PoweredByCNG wrote:
Guy_Arab wrote:...OR YOU HAVE A FAULT FOUR WAY VALVE


Can you please stop posting in CAPS?

Four way valve should only be suspected IF one or more air tanks don't fill.


Sorry but that is not the only problem take my word thirty years as a mechanical engineer on Mercs check your manual under faults
I have to say this but seen two many mercs with this problem seals on rubber boots give way on seals door problems are always four way valves can cause air fail to operate correct leaks in system some times could be problem
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Re: Air suspension for Merc O305

Postby amazon196969 » Sat Feb 24, 2018 12:40 pm

Thanks Guy_Arab and PoweredByCNG,

My bad...was the front not raising and not the left side...after 6 weeks of rain in my area I had put this job off until 3 days ago...I decided to just do it!!!the hardest part for me was building the ramps due to daily rain, as too much sloshy going on with too many hours wasted to get to required height.... doing it all on my own so lots of in an out of drivers seat to make sure it was just right, both height and safety wise) plan 'B' worked after a few hours of getting it to the right height and was finally able to grovel under the bus...I had been under the bus front of front wheels prior to ramping to see if I could identify the issue...I did see a lever of sorts dangling down central to the front wheels and suspected it to be the issue as I didn't recall seeing it while under there prior to this issue...so once I got her ramped up and got under her it was literally a 2 min fix or the leveling valve...and now feel the hours I spent on the ramp paid off...plus while I was under there I got to chisel off years of grease n dust that had accumulated on the internals of the wheel area...even unveiling the grease nipples...so the grease gun will be coming out today...then off to attempt to locate the oil, fuel, gearbox and air-compressor filters and oil pump...I noticing that engine oil pressure was high while building ramps, scarred me a bit so the oil filter and pump location and inspection/change is a must do ASAP...
thanks again for your info, much appreciated...
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