Coat Oring with RTV? Pittiing in bore where oring seals.

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I am in the process of changing the coolant pipes under the intake manifold of a BMW M54 engine. I have successfully cleaned out the broken plastic that was left behind but was still left with melted on oring material inside the bores. I cleaned out all the remaining material using a scotchbrite wheel on a dremel.

Now that everything is clean it's obvious that the area where the oring seats has become pitted from corrosion.

I've posted this on a BMW forum and it seems many recommend coating the oring with RTV to ensure a seal. I was always taught that putting any type of sealant on an Oring is wrong.

Will a new oring seal against the pitting? I really would like to avoid using any RTV if possible.

What is the best solution to ensure a leak free seal?

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I'm thinking more along the lines of:

  • Repair bore with cold welding compound or epoxy.
  • Repair bore by boring and sleeving (assuming parts are removable) or possibly welding (TIG?)
  • Something more along the lines of #2 or even PST.


I don't really think RTV would work that great...

How tight is the fit?
 
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The bores are part of the cylinder head and are not removable. They are in a fairly tight area and there is no room to get a tig torch in there or any way to repair the bore with any accuracy. In order to clean them out I had to use a right angle attachment on a dremel.

Apparently this is a fairly common issue on BMW's. One person said the orings will seal fine dry even with the pitting. Others claim to have coated the orings with rtv and have had no problems for several years afterwards.
 
There are quite a few ways to repair this sort of damage, I have done a few on old irreplaceable castings. The easiest way is to sleeve it with a stainless steel sleeve if you can find one the correct size, there are many to choose from. Measurements must be exact but chances are you can find one. these are normally used on shafts for seals but they will work on things like this also. use a sealer when installing.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=2ahUKEwiC_bqmtpXlAhURUt8KHbPEC6oQFjACegQIBhAB&url=http%3A%2F%2Fwww.skf.com%2Fbinary%2F21-128020%2F11337_2-EN-SKF-Speedi-Sleeve.pdf&usg=AOvVaw2EHLoD0mXN8QgrtJtSfebg

The next way is to use an aluminum filler, let it site for a while till it thickens slightly then use your finger (use a nitrile glove) and wipe it around the inside of the bore without too much build up, it should just fill the damage, leave it 24 hrs then carefully hand sand it with 220 the 400 grit wet and dry.
Coat the O ring with Hylomar M and install.

https://www.amazon.com/Hy-Poxy-H-45...mp;psc=1&refRID=NBMEKJCXE41WV70W8ETH

The other way is just to fill the damage with Hylomar, coat the ring with it and install. it will work and does a much better job than any rtv.

https://www.ebay.com/itm/Hylomar-M-2-7-Oz-Tube-61324/182550715886?epid=21017022178&hash=item2a80deddee:g:VE0AAOSwjBRdcyP0
 
The pipes do fit tight and there are 2 orings on each end of the pipe that seal in the bore.
 
I am little concerned with the aluminum filler's long term durability. Will it withstand the heat and exposure to coolant without breaking down?

Thank you for the hylomar suggestion. I will look into it.
 
The GM 3800 V6 has very similar coolant bores in the lower intake manifold, accessory drive belt tensioner, and water pump. To seal against the pitting in the aluminum bores, we coat the bores and the o-rings with Dow Corning 111 silicone grease. It's a high viscosity grease with excellent adhesive properties that is unaffected by hot water or coolant.
 
Originally Posted by newspeed
I am little concerned with the aluminum filler's long term durability. Will it withstand the heat and exposure to coolant without breaking down?

Thank you for the hylomar suggestion. I will look into it.



The stuff I linked to has a temp up to 250f and has very good resistance to water and chemicals like oil and grease.

http://www.hypoxy.com/images/Hy-Poxy TDS H-45 & H-450 Alumbond .pdf

I used a product called Aluma lead which is not made anymore but I repaired a crack in a primary cover on a BSA Lightning and you couldn't tell it had been repaired, it didn't weep or look out of place when polished.
If nothing else it will stop further corrosion. BTW Hylomar works fantastic on O rings. I use it to seal leaky pan O rings on some Euro oil pan level sensors instead of dropping the pan or pulling the engine to do it.

Its a bit of tricky repair getting it in right after where the ring sits but doable and it holds the life of the engine. Have no reservations using on the rings.
 
Originally Posted by andyd
I'm a broken record. The needle is stuck on " permatex aviation forma- gasket. It is available everywhere.


Which is similar to Hylomar M, Hylomar has/had builder approvals.....IIRC from Jaguar & Rolls Royce.
 
Originally Posted by perfect_oil
The GM 3800 V6 has very similar coolant bores in the lower intake manifold, accessory drive belt tensioner, and water pump. To seal against the pitting in the aluminum bores, we coat the bores and the o-rings with Dow Corning 111 silicone grease. It's a high viscosity grease with excellent adhesive properties that is unaffected by hot water or coolant.

Done it and works well.
 
It is one of a few things either lack of cooling system maintenance, wrong coolant or material failure due to galvanic corrosion or a combination of any of them. Some grades of aluminum corrodes more readily than others, anodizing parts can help address corrosion issues but not completely eliminate it.
 
Thank you all for the advice and suggestions.

I'm debating between the DOW 111 silicone grease vs Hylomar. I'm sure both will work but am heavily leaning to using Hylomar M. After doing much research it appears to be a good product for this purpose as it's non hardening and Hylomar approves its use on rubber orings. I also learned that Mazda factory specs Hylomar as the approved sealant to use on the water sealing orings of rotary engines.
 
There is no better product for this job, it will seal it permanently, no doubt in my mind whatsoever. I have used it seal some bad hard to seal O ring and gasket leaks eg engine vacuum pumps and they are still tight as a drum years later.
 
Originally Posted by Lubener
Originally Posted by perfect_oil
The GM 3800 V6 has very similar coolant bores in the lower intake manifold, accessory drive belt tensioner, and water pump. To seal against the pitting in the aluminum bores, we coat the bores and the o-rings with Dow Corning 111 silicone grease. It's a high viscosity grease with excellent adhesive properties that is unaffected by hot water or coolant.

Done it and works well.

I have replaced the plastic coolant elbows on our Buick 3.8l , with metal elbows . They have a single O-Ring . Just wet the O-Rings with coolant .
 
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