Need a little help with the 420 sel!
 

I have bought a 1987 420 sel. my problems are ...1) I have to fill it up with oil more than twice a week. 2) my fan makes funney sounds and starts and stops spinning(I think i need a fan cluch). 3)idle problems. However bad this sounds, the car runs good. I'am trying to restore the best i can. I put new brakes,spark plugs and wires,distruber,oil change with filter,new gas filter, transmission filter and front end alignment.MY questions are, what can i do to stop useing so much oil every week. i have 180,000 on this car and i want to keep it. Any insight would be very helpful.....

English Comp 101
 

1. Does the car smoke or drip oil?
2. Which fan, the electric one in front of the radiator or the engine driven one?
3. Is the check engine light on? I have yet to figure out how to read codes from these cars. There are many reasons for your idle problems. I'll get back to you on this.

Have you replaced any front end parts, ball joints, bushings etc?

When I bought my 1986 420sel it had about 180,000 miles and consumed a little less oil than yours, but still more than I thought it should. I tried RESTORE
in the engine and after that I haven't had to top up between oil changes.
Its in a metal can and costs about 10 bucks.

420 Sel
 

As far as the oil consumption goes Pull the heads ,replace the guides and stem seals reface the valves and seats and replace the timing chain and tensioner.
Unless the engine has been severly overheated the block and rings will be fine.
Regarding the fan; a properly working fan clutch will come in and based on temperature and RPM, If you have doubts about it have it checked out.
Good luck Mike

Benze- whatever you do don't give up. I just finished restoring my 1990 420 Sel and it was worth it. I had the same problems with the idle and then ran BG 5 a fuel system cleaner through three tanks of gas and this helped. There was a thread about this very subject last week and the general consensous had something to do with the intake valve seals, cups (?) cruise the search engine. Did you do the timing chain yet and motor mounts?

Wow- that's a huge expense recommendation- like $2000. I'd check to see that something more innocent- like a mis threaded drain plug. check your oil filter has a o-ring. Do the simple easy stuff first- then the bit more complex, then the serious expensive stuff. Of course unless you have a unlimited budget- then do what Mike says. You can check the fan clutch by holding it with your hand- have someone start the car while you are holding the fan- if you can hold it easily, then yes you need a new clutch. The tougher it is, the less you need a clutch. You should still be able to stop a fan with a brand new clutch. Obviously be very careful doing this. If you are not mechanically inclined at all; well... dont do any of this.

I would like to say thank's for all the help and i will not give up on this wonderful machine! I will check all the easy stuff first cause i do not have
a bunch of money,but i can make it happan. thanks for all the help

I have two 87 420s. They are without a doubt one of the finest cars MB every built. Having said that, you need to be a better than average mechanic to keep them up without spending a fortune on labor. Most things can be done yourself and anything your not sure of, you can find many opinions and answers on this web site....it's a great place to talk to people and find solutions. I have saved myself tons of money by searching threads and finding short cuts to various problems. I think the number one thing to remember with these cars is to change the timing chain and guides every 100,000 miles. I have 240,000 on my blue car and did a valve and guide job at 201,500. The lower end of these engines are pretty bullet proof if properly maintained through oil changes. I do everything myself. I am about to change out the transmission on my blue car in my garage. It is the original one and getting a little loose. Fast idles are coupled with several reasons that are answered thought various threads. Simple checks include throttle cable, cruise ctl amp, etc. Oil usage sounds like a head job is needed. Once you do that the car will amaze you with performance. good luck...

I would start with a fresh oil change, and clean the engine to see where any leaks are coming from. Diluted and old oil can cause high consumption, and the valve cover gaskets are prone to leak.

Oil
 

You should tell us is the engine oily or is the car really using it? Sounds like a large leak,or use,though we don't know what kind of mileage you are talking about.JNT:rolleyes:

I often hear of the 4.2L V8 using/leaking oil, but not too much about the 3.8L using/leaking oil. Same story for my 380SE (3.8L), as I have nearly 270K and I do not have any oil leaks/usage.

What was the change on the 4.2L that seems to be causing this?

I was thinking of someday upgrading to a 420SEL and would like to know. :confused:

oil leak or use?
 

Most of the oil consumption is due o the valve guides,that and the rubber seal on top of the valves,the guides are of a softer material in that link so will be the first place to wear. The replacement of the rubber will reduce consumption.The guide will also effect the balance of you idle, look at it in a stick drawing,up side down T,the guide helps to hold the valve seat and face of the valve flush to one another,If the guide is worn it will allow the valve to travel off center of the seat and leak ever so slightly,this will cause a roughness in idle.JNT:D