Valve cover

[Harro10]

I brought my 1989 560sl (had it for one year) for the state inspection and the mechanic said that there is a slight leak from both valve covers. My son and I are going to change the valve cover gaskets. He ordered the gaskets from the nearest dealership and will pick them up today along with some copper crush washers. The 560 has 63000 miles on it. What should we look for when we have the valve covers off? We have no previous repair records on the car so I do not know if the timing chain has been replaced. What should I look for to tell if the guides are worn?
Thanks for any advice.

[230/8]

Considering the age of the car you should probably look at the upper cam chain guides for any signs of wear or severe discoloration that suggests they have become brittle. Deep wear grooves are a warning sign as well. The double-row chains themselves seldom fail, but the upper guides are plastic and prone to failure when old and hard. When they break it is common for the loose piece to lodge between the chain and sprocket causing a massive failure and an expen$ive repair bill. These are not too hard to replace, but sometimes getting access to and extracting the guide retainer pins can be a problem for a novice with butterfingers.

Also, spend $10 for new plastic oil tube connectors. This is really cheap and easy so just do it. The camshaft oil tubes do not fail, but the plastic connectors to the camshaft journals become brittle (they are brown so always look old) and will fail when cold oil at high pressure causes them to break loose. This will lead to rapid cam failure. Carefully pull the oil tubes off, a screw driver may be used to pry them up, and use an 8mm open end wrench to slide the plastic bits off the steel tubes. Install the new bits, clear the oil holes in the tubes and carefully check the oil holes in the cam journals for any plastic debris off the old connectors and clear out as needed, then carefully use a plastic mallet to snap the renewed oil tubes back in place.

While the cam covers are off, look carefully at the head castings where the chains move down into and up out of the head and timing cover. See if there is any sign of wear on the head casting from the chain slapping briefly when the engine first starts. If so, you will need to replace the chain tensioner, or have it done...ASAP. Finally, if this is being done by a MB shop, have them check chain stretch (wear) and if more than 4-6 degrees they can quickly install a new chain by threading it into the engine as the old one is removed. With only 63,000 miles this is probably not an issue. Another option is to install offset woodruf keys, but the new chain will likely be cheaper.

[Harro10]

Thanks 230/8, that was very helpful. I called the Parts Dept at the dealer to order the camshaft plastic oil tube connectors. They had no idea what I was talking about and wanted me to come in and identify the part on diagrams. I called back later and spoke to the Parts Dept Manager and he knew exactly the part you described.
Thanks again.

[Strife]

I have had the worst luck with valve cover sealing, even though I've done it "right", copper washers, torque wrench, cross-torquing in steps. I've discovered that even if not overtorqued, the gaskets after installation and use will develop a "ridge" where they meet the head lip and if you don't put a used gasket EXACTLY where it was before everywhere, it won't ever seal again. This is actually not easy to do.

However, I have not used MB OEM gaskets.

A comment about the oil tubes: make certain that they are down ALL OF THE WAY when reinstalling. They should be completely and entirely in the "V" of their cast-in holder and not be "wiggleable" anywhere. BAD THINGS will otherwise happen down the road.

[Harro10]

Hopefully I will get it right the first time and will not screw up the gaskets. It is a job that, in theory, should be simple but we all know how that can go. I appreciate the tips on the connectors. Once I actually get the parts and open the cam covers I am hoping the procedure becomes a little more intuitive.

[donbryce]

When I did my oiler tubes, there was at least 1 of those brittle plastic connectors that disintegrated on removal, on each side, and several tiny pieces fell into the oil holes in the head Despite my efforts to be gentle when prying them out, it was extremely hard to avoid this. I fashioned a series of decreasing diameter tubes/hoses into the shop vac ending with a piece of that hard plastic vacuum line, so I could thoroughly get out the debris. I suppose it would get washed out anyway in the oil stream, but I feared a piece blocking one of the oiler tube holes. The engine ran/runs fine, so I guess I did OK....just something to consider.

[rowdie]

I know that no sealant is recommended but after having the gasket roll or drop off I use it. I thoroughly clean the valve cover. Then I use a thin layer of sealant to affix the gasket. I place the cover on a flat surface and wipe off any excess. Let it set till the next day. Using paper towels I absorb any oil in the head, especially at the lowest point in the rear. I then use a rag with cleaner to make sure all traces of oil are removed from the head mating surface. Then using my finger I put a very thin fim of sealant on the gasket. Install the cover finger tight and come back and torque with new crush washers.
They never leak.

[Harro10]

Thanks Don and Rowdie. That all sounds like good advice.

[Strife]

I don't like the idea of using sealant, because of it's tendancy to come off and wind up where you don't want it. I found some RTV in my oiler tubes on the 380, I guess the previous owner was a bit overzealous with it . Fortunately, there hasn't been a further sign of any.

[rowdie]

I use a very thin film wiped on with my finger. Mainly to keep the gasket from slipping off when installing the cover.