94 E420-Oil Pressure Sender Location? - PeachParts Mercedes-Benz Forum

wjm · #1 06-16-2005, 08:45 AM

Folks,

At hot idle, my oil pressure drops to zero. After some research here, I figured it could be 1 of 4 things:

1) Oil filter not properly inserted in housing.
2) Bad oil pressure sending unit
3) Bad oil relief valve (in filter housing)
4) Bad oil pump

I sorted the list in order of cost and pain. I've re-adjusted the oil filter and will go on test drive shortly.

In case that does not work, I want to replace the pressure sending unit. I've check alldata DIY as well as the Mercedes CD and cannot determine exactly where it is on my vehicle.

Can someone tell me where to look for it?

How much work is involved to replace it?

Thanks!

maggie11_6 · #2 06-16-2005, 12:41 PM

wjm · #3 06-16-2005, 12:43 PM

Maggie,

Was my question amusing?

deanyel · #4 06-16-2005, 12:51 PM

It's probably a couple of hours of work - not real difficult but a little messy. It's located at the base of the oil filter housing. Access is from underneath. You have to drain all the oil, remove the filter from above, clean out the filter housing from above, then remove the filter housing from below. It's held in by 3 long allen bolts. You'll need a allen wrench attachment for your rachet - 5 or 6 mm as I recall and a couple of extensions. You have to disconnect a wire from the bottom of the alternator - no big deal. With the oil filter housing off it fairly self explainatory as I recall. You'll need a new gasket for the oil filter housing - $5 or $10 as I recall. If you're sure that's the problem it can probably wait until you're due for an oil change.

wjm · #5 06-16-2005, 01:13 PM

Thanks.

So, changing the Pressure sending unit really requires the removal of the oil housing?

Wow. I knew I'd have to do that for the oil pressure relief valve.

Is it visible (Pressure sending unit) from underneath the vehicle?

I understand that this is what the part looks like:

deanyel · #6 06-16-2005, 03:20 PM

You're right - I was doing the check valve. The pressure sending unit is right there but doesn't require the removal of the filter housing. Good thing you're watching me.

wjm · #7 06-21-2005, 04:19 PM

So, basically still have my question unanswered. Anyone know where the pressure sender unit is for my vehicle (94 E420)??

wjm · #8 07-17-2005, 07:54 PM

OK, pressure sender switch found. After taking off the engine cover under the vehicle, I was able to find it below the oil filter housing.

It was a bit tight getting to, but I was finally able to get the old one off. I decided to try it without draining the oil, so I was expecting quite a bit to come out... but it was not as bad as I expected. I was able to get the old one off and the new one on (hopefully tight enough). In any case, my problem is resolved. My oil pressure was showing at 0 during idle and 3 when accelerating. Now, after car has come up to temperature, it sits right above 1 during idle.

Note: It's best to disconnect the battery when doing this job. The Alternator wire is very close to this area.

Thanks all!

djcheek · #9 07-18-2005, 09:04 PM

Out of pure curiosity, how many miles does your 420 have? We have one that is displaying similar oil pressure problems with 129,000 miles. We know that the problem is the oil pump though due to the "chatter" when warmed up at an idle with the needle on 1. We are going to due an oil pressure test on it though, to confirm or disprove our theory.
Thanks, Di

Arthur Dalton · #10 07-18-2005, 09:21 PM

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1D00YU6RY1KI19M3RI&year=1994&make=MB&model=E-420-001&category=A&part=Cam+Oil+Line+Fitting
Do a search on "oil tubes"

M119 Camshaft Oil Tube Replacement on M119 / W124

wjm · #11 07-18-2005, 10:00 PM

Quote:

Originally Posted by djcheek

Out of pure curiosity, how many miles does your 420 have? We have one that is displaying similar oil pressure problems with 129,000 miles. We know that the problem is the oil pump though due to the "chatter" when warmed up at an idle with the needle on 1. We are going to due an oil pressure test on it though, to confirm or disprove our theory.
Thanks, Di

I have about 110k

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