Often read posts on forums warning us not to use RTV sealants on engines. Reason given usually because bits of silicone will possibly block oil passages.

Currently doing some work on my 98 E320. On this car, the valve cover is in two parts and the oil sump has two parts - an upper and a lower sump.

In both cases, there is no gasket. MB's instructions say to apply an RTV sealant and bolt together. Sealant is MB part number 003-989-98-20-10 which is is Loctite 5970 (RTV).

No choice but to follow MBs instructions, but seems we have double standards

Attached Files

Remove_install bottom part of oil pan.pdf (89.5 KB, 205 views)

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

I once tried to find that prohibition in MB literature, and could not find it. I think it specifically and only applied to the turbo-diesel engines? The danger, theoretically, is that if the oil filter gets plugged and goes into bypass mode, a piece of RTV could clog an oil jet that supplies cooling oil to the bottoms of the pistons, and your piston would melt.

In your case, use the RTV sparingly, consider changing the oil filter immediately after the first drive once the engine is back together. Probably overkill, but filters are cheaper than engines. Does your engine have oil cooling jets for the pistons? That could be the difference.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

The only way to get my om603 valve cover to seal properly long term is with RTV.

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CENSORED due to not family friendly words

The MB work instructions include a picture of EXACTLY where to apply the sealant AND the size of the bead. When applied correctly you'll have no trouble..........

Changing the oil right away is a waste of oil and filter, stick to regular changes. Besides, new RTV applied excessively will stay put for thousands of miles.

Used properly RTV is a non issue. When applied to flat surfaces, very little is needed as most of it will squish out.

As mentioned, mostly problems are caused by too much being applied so it mooshes out when the job is buttoned up .

FWIW, some years ago Permatex introduced a new sealant called " The Right Stuff " , it comes in a tube and a aerosol can with a long & narrow applicator tip you poke a tiny hole in so it only loads out a thin bead, no mess , no problems with little balls of sealants clogging the oil intake screen .

It is also hands down the very best sealant I have ever used, I hate sealants but every so often you get a gasketless thing or a alloy surface some DOP/DPM gouged that won't stop weeping and this stuff will fix it .

The can is still use full TEN YEARS LATER too ! you simply leave the applicator tip full and the next time you need it, remove and easily push put the plug of old unused sealant, re install the applicator tip and you're off to the races .

NOT CHEAP but you'll never be satisfied with anything else once you try this .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I've never let an oil filter go past 4K and install a new one at each oil change. Heck, I even change the fuel filter at that interval too.

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84 300SD
85 380SE
83 528e
95 318ic

If you use RTV on the valve cover, both halves has to be oil free. Don't know about the 98 E320, on the 617, you must soak up the oil in the head first, then degrease with brake clean otherwise it keeps dripping off the air cleaner side of the head.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

The type of fuel system on the engine matters in relationship to oil change intervals.

When using regular oil, a carb / early non feedback FI engine 4 K is fine. With feedback FI , 5 to 6 would be better.

With synthetic I push Dads 99 Blazer 4.3 V6 to 8 or 9 K. ( I bought it with 125 K miles, had coolant leak to oil from the intake manifold, motor not damaged but I gave it a rebuild, now has about 205 K and is still fine. )

Torquing the fasteners on an assembly down to full spec while the RTV is still wet causes most issues. Hand-tighten to a 1/8 or 1/16" or 2mm or whatever gap, so contact all around and an even layer of RTV is forming a gasket, but not squishing it out. Then STOP, wait full cure time according to instructions on RTV. Once cured, then torque fasteners to full spec.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

Yes, exactly as I do. Makes sense if you think about it.

I find that its best to follow the procedure written on the package of the RTV itself.

on some sealants they say to tighten to full torque immediately, some say to wait for a skin time, some say to tighten in 2 steps over a longer period of time.

I have never had a problem with any product as long as it was applied properly and the cure time followed as described.

The trick to success is cleaning the surfaces very good (final wipe with acetone or something) applying the exact width and volume required and extra where specced by the manufacturer.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Almost. Not the oil filter, it's the oil pickup screen in the sump that's the concern, at least when installing an oil pan. It has happened plenty of times, where an oil sump is installed using RTV sealant, and a long bead of sealant squeezes out into the sump. The hardened ribbon of silicon clogs the pickup screen, and the entire engine seizes up and dies due to lack of oil.

The key is knowing how much to use, and following the application and curing instructions. Because its so sensitive to the application technique and skill of the installer, and the consequence of doing it wrong is so high, it's not unreasonable at all to recommend avoiding it period, especially to amateur hobbyist mechanics seeking help on an internet forum.

Besides, there are so many modern non-setting sealants and other similar specialized gasketing products these days that are a superior choice.

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1998 E300 turbodiesel

America's Rights and Freedoms Are Not The Enemy!

This depends on the type of sealant being used. If you go through all the Permatex products, you will find that some say to torque immediately, others say to allow some time then torque. As always, read and follow the product instructions. (see bottom of post)

The type of sealant MB uses on the W210 breathers on the valve covers has to be torqued immediately. This is a form in place gasket (FIPG). There is a groove in the cover that has to be filled with a 2mm bead, then withing 5 minutes put in place onto the vee shaped rim that pushes into the groove. Then immediately torqued to spec.
Looks like this one (Not Mine - borrowed from PP!):

The OE sealant is actually Loctite 5970 (MB 003989982010) and is used in many applications on Benzes - Universal sealant (it is an RTV) There is a similar aftermarket sealant called Reinzosil that specifies same process. Both of these claim resistance to synthetic oils. Most of the Permatex products do not mention synthetics. Permatex does have a new product called Ultra Synthetic which is apparently formulated for use with synthetics (not yet available here)

After dismantling my original breather covers, there was silicone on inside hanging loose. Some may have already fallen off. This in an area that is open to timing chain and valve train.

I don't think much of these M112 glue on components!

From Permatex Technical Data Sheets:
Ultra Copper - Retorque not required
Right Stuff - Retorque not required
Ultra Black - Assemble finger tight, then retorque after 2 hrs
Ultra Grey - Retorque not required
Others can be looked up on Permatex site under Technical Data Sheets (TDS)

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5