I have heard different schools of thought on this one. Do you always use gasket sealant when replacing a gasket?

I have heard some say that it was only needed on the old cork gaskets. Others, say it should always be used.

If you do an extensive prep cleaning and with the new style of gaskets (fiber with a slick side) is gasket sealant really required or maybe even detrimental in some cases?

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Sam

84 300SD 350K+ miles ( Blue Belle )

Depends on the gasket. Water pump gaskets get aircraft type Permatex (the liquid paint-on stuff). Rubber gasket get nothing. fiber gaskets for things like vacuum pump get permatex, too, unless factory coated like the oil filter housing gasket. Only a thin layer, none should squeeze out.

NEVER use ANY sealant on MB head gaskets, they will deteriorate and leak. Any sealant required is applied during manufacture.

Do not use silicone sealants unless factory recommened (RTV is used in several places, but get the correct stuff, blue or orange silicone is NOT the correct material). I've seen cranks broken because a blob of silicone sealant got in the oil passages and cut off the oil to a journal.

I always clean surfaces before reassembly. Water pumps, etc get cleaned with rubbing alcohol, other get scraped or cleaned with carb or brake parts cleaner.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I have found these type gaskets are PURE CR@P. I have never been able to completely seal one, ever.

As for other gaskets, I usually apply a thin coat of sealant based on what the gasket does (Oil, coolant, etc.). I NEVER use sealant on headgaskets.

Most of all, proper torque is the key to good sealing.

The quality of rubber based gaskets and seals available for the OM 616 in India is not really that good plus the atrocious conditions make them worse so I use a Japanese product called Tri-Bond with very good results, on the HINO engine, Tri-Bond is used in quite a lot of places instead of gaskets and that is how I discovered this wonderful product.

Of course I use gasket sealant. On a bagel with an egg and bacon. Nothin better.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

I use gasket glue most of the time, but I will use a sealant if it is called for...

I am an advocate of using Permatex Hylomar on just about anything. It is a non-hardening rubberized paste-like thing that seems to work well. Parts come apart later if you need to disassemble. No set-up or drying time. Does not harden up in the tube like dreaded RTV.

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80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)

I try not to use sealant on anything except newer motors where that's what the factory used as a gasket. In fact, I try not to use anything on any pre-made gaskets except 3M Super Weatherstrip Adhesive when I can't get a gasket to stay in place on it's on long enough to bolt it up.

Recently, I did a search (MSN) on gasket technology. Here were some things mentioned...... Gaskets experience fatigue due to shear from the expansion rates of different components while heating and cooling. Also, there are new "layered" gaskets, rubberized fiber and silicone for example, that have been used to combat this. Consequently, it may really depend on gasket quality. Which may be hard to determine at times.

Not long ago, I changed the oil pan and gasket using one of the layered gaskets. I have not had much success, in the past, maintaining a seal in this area. Especially since it is subjected to extremes of shear and environmently. I decided to conduct an experiment by not using a sealant. So far, it is holding up like a champion.

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Sam

84 300SD 350K+ miles ( Blue Belle )

How about this stuff?

http://www.************************/ProductPage.aspx?ProductName=Silicone+Paste+Sealant&productid=105669&producttype=10

I've been putting it on all my gaskets.

Gasket "sealants" and other surface treatments are generally not a good idea. Obviously not appropriate - as noted - on head gaskets and/or rubber coated steel or rubber gaskets. On fiber based gaskets these coatings actually encourage torque loss. Reason is that the seal is accomplished by the load stored in a stretched (tightened) bolt. Bolts stretch when tightened and thereby retain and apply stress to the joint, pulling the flanges together.
Coatings tend to encourage lateral flow and/or crushing of the gasket material..so.. the gasket gets thinner, bolt stretch is lost, joint tightness is lost and...the dread drip begins. So, clean the flange surfaces well, install a dry gasket, and torque to specified load to impart the intended amount of bolt stretch. Use sealants only in specialized circumstances such as the "tee joint" where oil pan gaskets meet front cover and/or rear cover gaskets on some engines. Another exception in Gurkha's case as the stuff often sold in his country can use any and all help possible. Tri-bond is great stuff when the flanges are clean and dry and ideally designed for this approach.

Sorry for the epistle - yeah - I make and sell gasket material...someone's gotta do it!

Cheers all.

F

I use the Permatex high tack spray stuff on all paper gaskets, Nothing on head gaskets. Love Hondabond for all the stuff that calls for silicone sealant, great stuff.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Thanks FredMBurgess for confirming what I am beginning to find out about new gasket technology. Always, in the past, I was taught to use a sealant when installing a gasket. With the recent installation of a dry gasket on my oil pan and consequently no leaks, I am beginning to change this train of thought. A torque wrench, of course, is also the other critical factor in this. Maybe I can start solving more of the embarassing leaks.

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Sam

84 300SD 350K+ miles ( Blue Belle )

No worries, SD Blue. Sorry to all if my reply above seemed more like a speech...guess I've said it so many times to customers (gasket fabricators and OEM engineers) that it all just comes out like a sermon!

Anyway, yeah, more often than not the best solution is to clean the metal surfaces and install the gasket dry. Good gasket material will compress a controlled amount - allowing it to conform to the flange and also closing any pores in through the material.

Whoops - doing it again! ...I still have to spend some time fixing the leaks on my cars too. The driveway is starting to look pretty bad out there!

Good weekend all!
fmb

I use Toyota FIPG or permatex...

You can even use it where you have no replacement gaskets.
http://www.permatex.com/right_stuff/right_stuff1.asp
It will not fail you.