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Servicing the 420SEL

Posted: Wed 13 Dec, 2017 10:22 pm
by 420.SELect

I’m about to start a major service on my 88 420SEL but, before I fork out hundreds, I thought I would just get some advice/recommendations on the products/brands you guys swear by.

I’m going to dive in doing the Air/fuel/oil filter, engine oil, diff oil, transmission, bleed the brakes and flush the coolant.

There are a few service ‘packs’ on eBay that supply air/fuel filter (RYCO) and Nulon 10-40w oil but it seems like the Bosch parts are commonly in posts and videos I have seen.



Re: Servicing the 420SEL

Posted: Wed 13 Dec, 2017 11:04 pm
by Ivanerrol
Mann filters - Cheap and OEM. Bosch are not that expensive. Rebuilding your engine is expensive.
I'm not a fan of Nulon. Penrite oil - many use it here.

If you go to the stealership they will give you synthetic everything.
if you have a renovated engine or transmission this is fine otherwise stick to Dino or semi synthetic.

Don't get el cheapo transmission filters get OEM or Mann or Bosch.
There are on the NET original kits - filter and gasket or ring the forum sponsor MB Spares

The original DEX II for your car is allegedly NLA. you may need to go to DEX III.

I use either Penrite full synthetic or go to StooperCheap and buy the Chief (Mohican) fully synthetic.
I change engine oil every 10K's - an overkill but 300,000k's up on my W202 M111 and the engine oil came out clean every 10,000K's

You are aware the the timing chain guides on your car need attention at every 100,000K's

Mercedes coolant is Blue. If you don't have blue then change it out. Zerox G05 is either yellow or Green. It's almost the same but not quite.
There are endless stories of failed cooling system components. Just get the original blue stuff. There's Vaico or Stealership stuff. I pay 22Bucks a litre either at the stealership or a third party Benz supplier.
Don't forget fuel filters.

Should not cost you hundreds if you do these jobs yourself.

Re: Servicing the 420SEL

Posted: Thu 14 Dec, 2017 9:11 pm
by 420.SELect

Thanks for the information.

Penrite was the initial choice but I thought Id ask the group to see if there was a preferred brand I hadn't looked into.

I will get in contact with MB Spares regarding the Oil/Fuel/Air/Transmission Filters.

Yes, I have read many posts regarding the Timing Chain Guide - its a little out of my depth to be honest (at the moment anyway).
I will check the last time it was attended to and action accordingly

For piece of mind I just hit the stealership up for the correct coolant. Avoid any nasty situations (hopefully).

Can you suggest any other bits and pieces that should be on the preventative maintenance list that aren't super expensive.

Unfortunately, I think my Idle Control Valve needs replacing - going to try cleaning it first before purchasing - so thats going to be a hefty one.

Thanks again for your post.


Re: Servicing the 420SEL

Posted: Thu 14 Dec, 2017 9:33 pm
by Ivanerrol
Next step when you have a few spare dollars making a hole in your pocket is to change all the rubber components and vacuum tubing around your engine bay.
New Engine mounts and transmission mounts
There are nylon grommets on your gear shift linkage. These are very cheap but a PITA to change.

The timing chain guides are a specialist job. Ignore them at your peril. If one distentergrates then the costs of repair probably are much more than the car is worth.

I.M.H.O. The 420 W126 is one of the great Mercedes.

Re: Servicing the 420SEL

Posted: Fri 15 Dec, 2017 8:14 pm
by 420.SELect
Yeah cool, I feel like this next one is going to be a 'divide and conquer' kind of job.

The engine and transmission mounts are easy to find but I think me and my engine bay are going to become very familiar after I try to figure where (and what) all the different rubber and vacuum tube parts are.

It appears that the US sites are a good place to sift through to figure all the different bits and pieces required, as they break down all the parts in terms of systems and their components. I feel getting one of the sought after W126 service manuals would be a worthy investment (and time saver); but 300 bucks - for the body and engine books - still hurts to think about.

Is there specific spots that you recommend I source these rubber parts and vacuum tube from or is MB Spares the people to speak to regarding this type of thing?

Yeah, I have read posts of guys doing the Timing Chain Guide themselves - I figured they must be mechanics or super savvy with benzs'

I would have to agree with you, Ivan. The look/style of the W126's is timeless and they are a joy to drive.
I have only had her for a few weeks now but have pretty much stopped doing everything (besides work) but researching Benz forums, looking for parts and looking at other Benzs' - I think this may get out of


Re: Servicing the 420SEL

Posted: Sat 16 Dec, 2017 12:43 am
by 420 SE
Another suggestion by many is to make sure your fuses are copper not alloy, it does often resolve a number of odd niggling electrical issues that may occur with the 126.

Re: Servicing the 420SEL

Posted: Sat 16 Dec, 2017 7:07 am
by 420.SELect
Awesome, thanks for the advice.

Ill do a fuse audit and replace any alloy.


Re: Servicing the 420SEL

Posted: Sat 16 Dec, 2017 11:05 am
by KimB
Hi Chris,

Welcome to the esteemed ranks of becoming an OZBENZ "W126 Nutter".

There are quite a few of us on this Forum who are W126 Nutters. We carry our name with pride! :love4:

Owning a W126 is not merely owning a's a way of ife! :glasses2:

May you have a long association with your 420SEL!