blowing smoke and burning oil

Assuming it has never been overheated (cylinder wall damage), this is usally caused by mormal wear of the valve guides. Comprehensive top-end overhaul including guides, some vales, chain, rails, sprockets, water pump, hoses, est $4,000.

Bill Ditmire Ditmire Motorworks,Inc.

425 White Horse Pike Absecon,NJ 08201 609-641-3392

Well, see, you said the magic word "SL" that says $4000 every time. What you need to say is "rusty piece of crap 280SEL 4.5" and we'll tall you how to fix it for $70.

Ok, well, not really but you have a couple of options here.

1) The nature of the problem.

Blue smoke is oil (just as white smoke is coolant, black smoke is fuel) and burning oil at startup and acceleration (you might see it on deceleration, too) so you're definitly burning oil.

There's two places oil can get by - the rings and the valves stems. If it's the rings you're looking at a compete motor rebuild or replacement. So you hope and pray it's the valves.

A leak down test will tell you authoritativly which one it is. $100 for one of those or thereabouts.

Now, if it's the valves the there's two things it could be - the guides or the seals. Mercedes are fairly notorious for eating valve guides but sometimes if they're not too far gone you can just drop in new valve seals - which you can do with the heads on - and that somtimes cures it for years sometiems till the guides go. Yours is burning quite a bit it from the sounds of things like so it's probably safe to assume guides than seals.

Now, here's the irony. The valve guides are about a buck or so and you need 8. Problem is that $8 worth of parts is right inside the middle of the head and so:

2) Other stuff you'll want to replace

The chain and timing rails should be renewed if you're gonna do the heads. While not partitularly dificult it's non-trivial and it's another $200 in parts or so. Note that this is probabaly only worth doing if you have the doubel row timing chain, if you have the odious single-row you're probably better off getting another engine than doing anything to this as that would be cheaper than repairing yours and converting it to double row.

3) Summary So, figure out parts and labour for the various bits you need. If you have a recently renewed double row chain and you know your chain rails are good all you need to do is the heads.

You can have your heads rebuilt, or you can buy used or reconditioned heads. Sometimes you see good heads for $300 a pair.

R&R of the heads will run you $500 - $1000 but you can do it yourself if your handy or have mechanically inclined friends. It's not terribly difficult *if* you're used to chaning cylinfer heads.

So there ya go. The cheap magic bullet is valve stem seals, $20 for seals, 4 hours labour to put them in if you're slow. But it sounds like your car has more than seal issues.

Next cheapest is to get a pair of cylinder heads for $300, $300 for gaskets, and you install them yourself or pay somebody $500 - $1000 to do it. But this presupposes your current chain is double row and in at least good condition. If not you're gonna add $500 - $1000 in labour and another couple of hundred bucks in parts so at thia point a good used motor starts to look attractive.

If it were me I think I'd look for a rusty low milage sedan someplace and buy it for the motor. And I absolutley would not use a single row 380 motor.

A 79K mi 560 motor is $2300 from

Figure $1000to swap it in. Hmm, they have lots of 500 and 560 and 420 good usedmotors but not 380s. What does that tell you?

Valve guide seals.

Thanks so much for that great info.

So it sounds like I could do 2 things

1) Replace the valve stem seals in a day for pretty cheap and see if that clears things up. If that doesn't do the trick I can:

2) Open her up again and replace the valve guides, which could take a good chunk of time.

My questions on #2 is how much time would the job likely take and could an amatuer with a lot of time and little money do the job myself?

btw: I do have a double row timing already.

Thanks again.

-Brian

That sounds abouit right. TO do the valve stem seals with the motor in place you have to blow compressed air into the cylinder to keep the valve close while you turn the engine so the cam isn't on it then you remove the valve. God help you if you drop the valve into the engine as you'll be fishing it out with a magnet on a wire for ages.

You can doit yourself but changing the rail guides needs some special tools and if you havn't changed a timing chain before doing a v8 like this is pretty not trivial.

If your chain and chain guides are good and all you have to do is break the chain R&R the heads and out it back then yeah go ahead and do that yourself or if you can find sombody close with the tools whose done it before that might work too.

I'm sure we can walk you through it if you wan to do all this by yourself though. I take it this is not a car you rely on for transportation?

WHat are you foing to do about the heads? Rebuild yours or get other ones? You need toget machine shop quotes in your area and look at prices for rebuilt heads.

Its always agood idea to get the cylinder at top dead centre, so if you drop the vavle it only falls 1/2" or so.

I never trusted air myself, and proper mechanics are going to laugh here, but when I take the valve springs off an engine, while it assembled, I get some nylon rope, like water ski rope, and feed some into the cylinder, then wind it over by hand to scrunch it up, so the valve has got no chance of going anywhere, changed the spring and wound it back by hand, pulled the rope out and moved to the next cylinder. Seemed to work Ok, but make sure the engine is cold.

I am now stand> >

Keen idea, Sir Alex!

mcbrue complimentingly under the bridge in the trailer down by the river

96 S420

An alternate method of using compressed air is a length of rope. Prior to rotating a piston to TOC, feed a piece of rope into the combustion chamber. It will fill the cylinder volume and not allow the valve to fall downward. You'll get the job done much faster without the hassle of using compressed air and fittings.

JR

| >>Thanks so much for that great info. | >>

| >>So it sounds like I could do 2 things | >>

| >>1) Replace the valve stem seals in a day for pretty cheap and see if | >>that clears things up. If that doesn't do the trick I can: | >>

| >>2) Open her up again and replace the valve guides, which could take a | >>good chunk of time. | >>

| >>My questions on #2 is how much time would the job likely take and | >>could an amatuer with a lot of time and little money do the job | >>myself? | >

| >

| > That sounds abouit right. TO do the valve stem seals with the | > motor in place you have to blow compressed air into the cylinder | > to keep the valve close while you turn the engine so the cam isn't | > on it then you remove the valve. God help you if you drop the | > valve into the engine as you'll be fishing it out with a magnet | > on a wire for ages. | >

| > You can doit yourself but changing the rail guides needs some | > special tools and if you havn't changed a timing chain before | > doing a v8 like this is pretty not trivial. | >

| > If your chain and chain guides are good and all you | > have to do is break the chain R&R the heads and | > out it back then yeah go ahead and do that yourself | > or if you can find sombody close with the tools whose done | > it before that might work too. | >

| > I'm sure we can walk you through it if you | > wan to do all this by yourself though. I take it | > this is not a car you rely on for transportation? | >

| > WHat are you foing to do about the heads? Rebuild | > yours or get other ones? You need toget machine shop | > quotes in your area and look at prices for rebuilt heads. | >

| >

|

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