1991 L98 Valvetrain Noise

[Coupe de jour]

I have a 91 Coupe with about 98,000 miles on it. It definitely has some valve train noise but I haven't had time to pop off the valve covers. Has anyone else had to readjust valves on the L98?

I recently put new Bosch injectors in it from TPIS which, in my case made less noise than the old injectors but the valve noise is even more obvious now.

My concern is that if I readjust the valves and I have one or more stuck lifters, will I cause serious damage to the valve train?

Thanks,
Coupe de jour

 

[spyysee]

What kind of noise?
the injectors make a ticking noise that can sound like valves.

 

[MBDiagMan]

I expect that if it sounds like valve train noise to you, then that is what it is.

I hope this dosen't turn into an oil thread, because that is NOT what I'm trying to do. I'm sure that you use a premium quality oil and hopefully you change it hot and change it often.

I bought my roller cam L98 Vette used and it had valve train noise. This is caused by gunk. I cleaned out the crankcase as I describe later in the thread and the noise went away. I would highly suggest that BEFORE you go to the trouble of adjusting the valves that you thoroughly clean the crankcase with some hot and frequent oil changes. If you don't and go ahead and adjust the valves, if the gunk gets cleaned out, the valves will then not be right. These hydraulic rollers just don't go very far out of adjustment.

What I would recommend to clean your crankcase would be to use a Universal grade oil and change oil and filter about every 500 miles for an oil change or two or until the noise clears up. Drain the oil when the engine is hot and has just been shut off. This way the contaminants and gunk will be suspended (stirred up) in the oil and will come out better when you drain.

Universal grade oils are those used by the Diesel Truckers. Although these oils are tested and rated for gas engines, they are developed with added detergents to deal with soot that is present in a diesel. They do a great job of cleaning a crankcase without the risk of using engine flushes that are basically solvents with no lubricating ability.

Examples of these oils are: Chevron Delo 400 Multigrade, Mobil Delvac, Mobil Delvac One (Synthetic) and Shell Rotella T. The last choice, Shell, has a higher parafin content so would not be the best choice for the purpose of cleaning your engine.

Once you have the engine cleaned out and the noise goes away, stay with your favorite premium motor oil and change it with a fresh filter often. If you don't drive the car alot, as many Corvettes including mine are used, set your oil change intervals based on time rather than mileage. Don't let it go over six months between changes.

If you take very short hops, like less than 20 miles, often, you are not boiling out the moisture and acids from the oil. This will lead to the noise that you are hearing.

Good luck,

 

[Coupe de jour]

Doc,

Thanks for the tip. What I have done so far is to run some Lubro Moly engine cleaner right before the oil change. The oil went from clear to jet black in 20 minutes. When I added the new oil I also used Lubro Moly's engine treatment. I have had good luck with these products in the wife's Mercedes.

After the treatment I still had the tapping noise. Have you ever heard of Rislone? I understand that it is pure detergent and can be added to the crankcase similar to your suggestion on the universal grade oil.

What interval do you change your oil at? I've run mine since the change for about 5500 miles (Mobil 5W-30 Synthetic) and it is still clean and the engine hasn't burned a drop.

Thanks again,
Coupe de Jour

 

[MBDiagMan]

I repeat, I would do 500 mile OIL changes, preferably with the Universal grade oil which is SUPER high detergent, high quality oil.

Rislone, the Lubro Moly treatments are basically SOLVENT, not LUBRICATING OIL.

Rislone was a very useful product in the days before engine oil evolved into the fabulous products that they now are. In the sixties and even in the seventies, engines gunked up so bad it was incredible. It was due partially to open crankcase systems but mostly due to the primitive oil that was used. Modern premium oil has the additive packages built in. Adding other additives will badly upset the balance of the additive package that has been so well engineered over the past 20 years or so.

You asked, so I'll tell you. I am an oil change maniac. Oil is cheap, engines are expensive. In my 300E MB that gets only highway miles I change oil and filter every 5,000 miles or six months, whichever comes first. In my Vette that only gets driven occasionally, I change oil and filter every 2,500 miles or six months whichever comes first.

As I described, I use Universal Grade oil, specifically Chevron Delo 400 Multigrade. I use this in everything on my place from Diesel tractors, to diesel cars and gas cars. The only other oil I use is Mobil One in my '01 MB C240. It came from the factory with Mobil One so I have stuck with it.

Additionally, I drain my oil when the engine is hot and let it drain overnight. This is how you get all the gunk out. The gunk is stirred up in the oil when it is hot, so it will drain out. Draining overnight gets the last few drops which are the real sludge anyway.

You already pay for additives when you buy your favorite premium motor oil. There's absolutely no reason to incur the added expense of additional additives. Most of them are snake oil anyway.

If you will change oil every 500 miles and drain it when hot, you will get your engine cleaned out safely in just a few oil changes.

My $0.02,

 

[Coupe de jour]

Doc,


Thanks for all the information. I appreciate the thorough explaination. Can I get the Chevron Delo 400 Multigrade at any Chevron station?

By the way, what year is your 300E? I have a 1990 300 SEL. We've enjoyed the car a lot but just recently lost the head gasket so I am going through that repair job. Since I live right in town with ARP, I brought them a head bolt and they came up with a 12mm head stud I can use. I am considering the Mosselman twin turbo setup and I found a trans kit for the 722.3 in the car. With the shift kit (softens up the 1st to 2nd shift among other things) and a first gear start kit from the Berg works, the car should be a lot more appealing to drive away from a dead stop.

Just as I have enjoyed this Corvette forum, I also enjoy the Shop Forum for Mercedes. It's a great place to get info.
Kurtvette

 

[MBDiagMan]

Kurtvette,

You can get Delo at about any Chevron station, especially truck stops, but the best place to get it is at Wal Mart for about $6.50 for a one gallon jug. They also have it in quarts but it is more convenient in the gallons.

My 300E is an '88 with a manual transmission. Only about 300 of them came to the US with manual transmissions. It has the same M103 engine as your S class car. It's a great car that I enjoy as much as my Vette.

The head bolts on the M103 are designed to stretch so that clamping pressure is maintained. They are angle torqued which stretches the bolt alot. I would be very careful when using other than the factory bolts because if they are not exactly the same metal, they will not take the angle torquing or they will pull the threads in the block. You can learn all about angle torquing at mercedesshop.com if you are not already aware of what I'm talking about.

The M103 is an amazing engine. Mine has 267,000 miles and still uses no oil between 5,000 mile changes.

BTW. I am the number one poster on mercedesshop.com where I go by my real name.

Good luck with your head repair on the 103 engine and let me know if you have any questions.

Have a great day,