Oil pan gasket vs RTV sealant - PeachParts Mercedes-Benz Forum

RML · #1 10-08-2015, 10:57 PM

I found the source of an oil leak on my 84 300D to be a small crack in the flat surface of the block where the oil pan flange meets up. I dropped the oil pan to get a better look and after cleaning everything I found that at some time under a previous owner, the area saw some trauma. The flat surface of the block was actually uneven due to the small crack and there was a bit of space between the oil pan and the block. It is right where the timing chain is on the inside. The bottom of the oil pan is not damaged at all but there is a dent and distortion at the flange. I cannot imagine what could have caused this. But anyway, I filed the block so it is flat and used some JB Weld to seal the hairline crack. I also hammered the oil pan flange flat again. To seal things up when I put the oil pan back on, I am thinking that I might be better off with something like RTV sealant like I used when I resealed my differential cover. I am concerned that if I have any distortion or unevenness, the oil pan gasket may not provide a total seal.

Has anyone sealed their oil pan this way? Results? Will I be able to get it off again?

Mxfrank · #2 10-09-2015, 07:33 AM

I don't see as you have any choice, since flatness can no longer be assumed. It will come off if need be.

leathermang · #3 10-09-2015, 09:22 AM

The problem which you read about with just using RTV is people think some is good so more is better...
What you do not want is any RTV to be squeezed out into the pan and then stop anything up... cured or not...
IF you can get that gasket in cork... or if you are good at cutting cork sheeting to the shape you need....
then what I have done for decades is to put as *** thin a coat*** of RTV ALL over that cork gasket and LET IT CURE overnight. Basically you are filling in those gaps in the cork...
So you have a springy gasket totally sealed in RTV...
then you clean up the metal surfaces with alcohol or acetone to where no discoloration occurs on a paper towel when you wipe it.
Then you again put the thinnest coat you can do... usually requires getting RTV on your finger.... and coat both sides of the prepared gasket and the metal surfaces needing sealing....
Then put it together making sure you do not over torque the bolts.... which is the most common reason gaskets leak...
Leave at least 24 hours to cure before putting fluid back into the pan.
A fussy messy time consuming method..(the waiting periods for curing mostly).... but with safety and physics behind why it works.

Dan Stokes · #4 10-09-2015, 09:34 AM

I'm not clear if you're talking about the upper or lower pan but it sounds like the upper.

The recommended sealant is designed to cure in the absence of air (anerobic IIRC). It's thin and requires a pretty flat surface. If you need to crutch the factory system due to damage I'd go with Leathermang's input.

If it's the lower pan surface you could replace the upper pan and have a proper sealing surface for the lower sump. I have done significant welding on my lower pan to fit it in the S-10 and it is probably slightly warped. I used the factory gasket and a SLIGHT coating of RTV as described and it works great - no leaks.

Dan

funola · #5 10-09-2015, 10:49 AM

RTV on oil pan gasket will do if you are careful and not have excess squeeze out FOD into the oil pan. Taking it off later will likely require a chisel or screw drive + hammer.

I'd recommend a non hardening sealant and get a new oil pan from the dealer. I hear they are not expensive.

Loctite Gasket Sealant, 7 fl oz Tube, Black 30515 | Zoro.com

gmog220d · #6 10-09-2015, 11:43 AM

I recommend Toyota Seal Packing #103. It's high grade black silicone, denser than most, and is what 'Yota sells for "oil pan gasket" for 22R and 22RE engines. If you walk into a 'Yota parts department and ask for a oil pan gasket for those engines a tube of this stuff is what you get. Good stuff.

Zulfiqar · #7 10-09-2015, 11:56 AM

Quote:

Originally Posted by gmog220d

I recommend Toyota Seal Packing #103. It's high grade black silicone, denser than most, and is what 'Yota sells for "oil pan gasket" for 22R and 22RE engines. If you walk into a 'Yota parts department and ask for a oil pan gasket for those engines a tube of this stuff is what you get. Good stuff.

Its the same quality as the MB and GM stuff - GM stuff is cheaper and a bit neater IMO (gray in colour)

For a non hardening but gel type sealant, nothing beats oldschool Rolls Royce Hylomar Blue.

as with anything concerning sealing with liquid - surgical cleanliness is required for good bonding,

SD Blue · #8 10-09-2015, 11:57 AM

To avoid some of the hazards of RTV sealants, I've been using Aviation Form-a-Gasket Sealant. It's non-hardening, available at numerous parts stores, and has been doing an excellent job of sealing oil leaks that I've had issues with.Gasket Sealants : Permatex® Aviation Form-A-Gasket® No. 3 Sealant Liquid

Previously, I tried the dry gasket set-up and haven't had long term success. I think that many of the aftermarket gaskets just don't seal as well, long term.

barry12345 · #9 10-09-2015, 12:35 PM

Main thing is to get all the oil residue removed. I suspect again without knowing that the really expensive sealers may have some chemical incorporated.

This to somehow work with a small amount of unclean surface. Many washes with laquer thinner on a rag is my approach. You just keep wiping things down until the wet or damp cloth in the final stages is perfectly clean. The thinner then totally dries out very fast.

This is where most gaskets shine. If there is a little oil residue it does not matter as much. Where chemical sealers demand clean. This allows them to bond.

Maxbumpo · #10 10-09-2015, 12:50 PM

RTV is supposed to be a big no-no on any engine part exposed to engine oil (in a MB engine). The theory is that a piece of excess RTV can somehow pass through the oil filter and then plug an oil squirter that is cooling a piston, and the piston overheats and seizes and then you have a doorstop.

Logically I don't see how this works, unless the oil filter plugs and goes into bypass mode. I suppose if you had a lot of RTV and other junk in the engine / oil and leave the old oil filter in place, it will quickly be overwhelmed and go into bypass mode, and then you get your very expensive doorstop.

Zulfiqar · #11 10-09-2015, 01:32 PM

Quote:

Originally Posted by Maxbumpo

RTV is supposed to be a big no-no on any engine part exposed to engine oil (in a MB engine). The theory is that a piece of excess RTV can somehow pass through the oil filter and then plug an oil squirter that is cooling a piston, and the piston overheats and seizes and then you have a doorstop.

Logically I don't see how this works, unless the oil filter plugs and goes into bypass mode. I suppose if you had a lot of RTV and other junk in the engine / oil and leave the old oil filter in place, it will quickly be overwhelmed and go into bypass mode, and then you get your very expensive doorstop.

all new MB engines are sealed with RTV type sealant now. it was the old times when they advised to use anaerobic flange sealant on timing cases and upper sumps. Basically anearobic sealant will run off with the oil flow as it cannot cure in air, It needs air to be removed for it to set up. I see it as a more elegant solution but it requires almost perfect machining to work. Sealants have also advanced with time, the new stuff is very good at almost crazy temperatures and resists oil/coolant etc.

Diesel911 · #12 10-09-2015, 02:52 PM

I have not read the other posts. When I changed the Turbo Drain Seals I did not plan on dropping the Oil Pan and did not have an Oil Pan Gasket. I ended up cleaning the old pan gasket and using RTV Silicon Sealant and have had no issues.

If you are worried about pieces of Silicon coming off be sure to wait several hours for the stuff to cure before pouring Oil into the Oil pan.
Once the Silicone is cured and a piece is sticking out if you pull on it acts somewhat like it is a rubber band and it won't detach easily.

Note that I removed the intact Oil Pan Gasket wiped off the Oil then sprayed it down with Brake Cleaner and let it dry in the hot Sun for 4 hours to get rid of the Brake Cleaner. Once degrease the RTV Silicon is going to glue itself to the Gasket. Meaning the oil is not going to seep between the gasket and the Silicon.

leathermang · #13 10-09-2015, 03:18 PM

Quote:

Originally Posted by Diesel911

I have not read the other posts......

WHY ? That hurts my feelings.... I wrote my post especially for YOU.

RML · #14 10-09-2015, 05:56 PM

Thanks for all the feedback. I am going to stop at the auto parts store on the way home and see what they have. I'll avoid the RTV if I can. I like the idea of a non hardening sealant. If need be I can let the car sit in the garage for a few days until I get the right stuff. Appreciate all the input.

RML · #15 10-09-2015, 05:59 PM

Quote:

Originally Posted by Dan Stokes

I'm not clear if you're talking about the upper or lower pan but it sounds like the upper.

If it's the lower pan surface you could replace the upper pan and have a proper sealing surface for the lower sump. I have done significant welding on my lower pan to fit it in the S-10 and it is probably slightly warped. I used the factory gasket and a SLIGHT coating of RTV as described and it works great - no leaks.

Dan

Not sure what you mean about upper and lower pan. I am only aware of one pan in the 300D.