Oil Pan Gasket leaking.. RTV?
01-02-08, 02:04 PM
#26
Racecar - Formula 2000
Your opinion obviously does not agree with mine, but the way I have stated it does work, and using a gasket doesn't. Leaving a layer of sealant is similar to using a gasket. It will creep and relax, leaving the engine mount bolts loose, and a leak will develop.
BTW, I do understand that the way you have described is the "standard" method of using sealant. For most uniformly loaded gasketing areas, that method will yield better results than "squeezing all the sealant out." However, in this case, it just doesn't work very well due to the vibration and loads from the engine mounts.
Last edited by DaveW; 01-02-08 at 02:30 PM.
01-02-08, 02:24 PM
#27
i havent heard anyone hear mention how to use rtv or gasket maker properly. the reason it works at all is because you have to let it set before you assemble and tighten your parts that way it provides a "cushion" between the two metal parts. If you assemble and tighten things immediately you will very definately squeeze it all out.
Follow instructions and you will find that most if not all recommend a 15 minute period for which to allow the sealant to "skin over" before assembling and another period of time about 20 mins before torquing fully.
That is the only way to ensure a good bond between surfaces and enough 'pillow' on which to keep surfaces separate.
do not tighten wet sealant or all you will get is blobs on either side of where you need it and nothing between.
Follow instructions and you will find that most if not all recommend a 15 minute period for which to allow the sealant to "skin over" before assembling and another period of time about 20 mins before torquing fully.
That is the only way to ensure a good bond between surfaces and enough 'pillow' on which to keep surfaces separate.
do not tighten wet sealant or all you will get is blobs on either side of where you need it and nothing between.
i am going to reseal my oil pan in a few weeks and i'm going to use a stock gasket plus a very thin layer of RTV on both sides of the gasket. i have heard of people having success with this approach.
01-02-08, 02:33 PM
#28
Racecar - Formula 2000
i have thought about this, as on the 4 motors i have assembled, i've always just immediately torqued the oil pan down... doing this makes the RTV just shoot out of every crevasse and even come out of the bolt holes while you're torquing them, which makes a mess and creates a much too thin gasket layer between the block and the pan.
i am going to reseal my oil pan in a few weeks and i'm going to use a stock gasket plus a very thin layer of RTV on both sides of the gasket. i have heard of people having success with this approach.
i am going to reseal my oil pan in a few weeks and i'm going to use a stock gasket plus a very thin layer of RTV on both sides of the gasket. i have heard of people having success with this approach.
Dave
01-02-08, 02:34 PM
#29
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if you do things right they will last a lot longer than combined methods that just end up compromising each other.
01-02-08, 02:45 PM
#31
Racecar - Formula 2000
01-02-08, 03:16 PM
#33
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No. simply because the mount that you speak of only anchors the entire motor. the problem with the rotary that causes leaking is slight shifting between rotor housings which result in an uneven mating surface for the pan on the bottom. the engine block of a rotary is made of several housings whereas on a normal cast cylinder block the mating surface on the block is all the same piece. the rotary oil pan gets to bolt to the bottom of all the different housings. thats why you will inherently have an uneven surface. i have been witness to a rebuild that was run and then removed after a few hours to have the bottom pan surface lapped smooth and then re-installed afterwards. i have nevevr heard of this being done elsewhere though and the thought was that most of the shifting would take place as soon as the engine was fired up and then settle so any "ridges" caused by housing shifts would be corrected right away. this is not cost effective whatsoever. as it involved removing the engine twice once to rebuild another to lap the bottom then re-mount the oil pan.
01-02-08, 05:51 PM
#34
There is metal-metal contact, but that obviously will not create a seal by itself unless the mating surfaces are machined to ridiculously high tolerances. We're talking about a sheet metal pan, which flexes and has imperfections, so sealant needs to be applied. When you torque everything down, the sealant is squeezed out, but some stays in the tiny gaps formed by the imperfections in the pan and block/f cover. The tiny amount of sealant that stays is what creates the seal. The direct contact between the pan and block is what stops any compression that would happen with a gasket.
The bolts stay tight and the sealant stays happy. End of story.
01-02-08, 05:57 PM
#35
Racecar - Formula 2000
Sorry, but you just need to stop putting BS out there. If you're trying to understand it, just say so, but what you're doing is making ridiculous statements.
There is metal-metal contact, but that obviously will not create a seal by itself unless the mating surfaces are machined to ridiculously high tolerances. We're talking about a sheet metal pan, which flexes and has imperfections, so sealant needs to be applied. When you torque everything down, the sealant is squeezed out, but some stays in the tiny gaps formed by the imperfections in the pan and block/f cover. The tiny amount of sealant that stays is what creates the seal. The direct contact between the pan and block is what stops any compression that would happen with a gasket.
The bolts stay tight and the sealant stays happy. End of story.
There is metal-metal contact, but that obviously will not create a seal by itself unless the mating surfaces are machined to ridiculously high tolerances. We're talking about a sheet metal pan, which flexes and has imperfections, so sealant needs to be applied. When you torque everything down, the sealant is squeezed out, but some stays in the tiny gaps formed by the imperfections in the pan and block/f cover. The tiny amount of sealant that stays is what creates the seal. The direct contact between the pan and block is what stops any compression that would happen with a gasket.
The bolts stay tight and the sealant stays happy. End of story.
Dave
01-02-08, 06:01 PM
#36
Yea, im all with DaveW. RTV all the way. Just make sure you get the motor mounts bolted on there as well as all the pan bolts or else there is no way your gonna stay leak free. I even installed the motor mounts while the engine was still on a stand while I let the RTV set up, Then I pulled them off and dropped the motor in and bolted them back up and its been leak free for about a year.
01-02-08, 06:02 PM
#37
i havent heard anyone hear mention how to use rtv or gasket maker properly the reason it works at all is because you have to let it set before you assemble and tighten your parts that way it provides a "cushion" between the two metal parts. If you assemble and tighten things immediately you will very definately squeeze it all out.
Follow instructions and you will find that most if not all recommend a 15 minute period for which to allow the sealant to "skin over" before assembling and another period of time about 20 mins before torquing fully.
That is the only way to ensure a good bond between surfaces and enough 'pillow' on which to keep surfaces separate.
in every case i know of, properly used gasket sealant has outperformed conventional gaskets with obvious exceptions of course such as head gaskets, etc.
do not tighten wet sealant or all you will get is blobs on either side of where you need it and nothing between.
There is also the option of using ready cork/rubber gasket roll and cutting out your own which has also proven quite effective.
Crush type gaskets (most metal ones) are also not intended to be re-used and often call for replacement that is because upon torquing you "set" the gasket and by re-using it you can develop "wrinkles" in it by attempting to "reset" it. this is not good. so just splurge and buy new ones or go with a proper rtv and follow all directions for your application
Follow instructions and you will find that most if not all recommend a 15 minute period for which to allow the sealant to "skin over" before assembling and another period of time about 20 mins before torquing fully.
That is the only way to ensure a good bond between surfaces and enough 'pillow' on which to keep surfaces separate.
in every case i know of, properly used gasket sealant has outperformed conventional gaskets with obvious exceptions of course such as head gaskets, etc.
do not tighten wet sealant or all you will get is blobs on either side of where you need it and nothing between.
There is also the option of using ready cork/rubber gasket roll and cutting out your own which has also proven quite effective.
Crush type gaskets (most metal ones) are also not intended to be re-used and often call for replacement that is because upon torquing you "set" the gasket and by re-using it you can develop "wrinkles" in it by attempting to "reset" it. this is not good. so just splurge and buy new ones or go with a proper rtv and follow all directions for your application
I'll admit that I never heard of letting RTV cure a little until you just said that. The TDS sheets on permatex.com do say that.
Some applications might benefit from a short cure time, then torqueing, but I think this is a special case where metal to metal contact is desired because of the motor mounts.
....aaaaand
/geek rant
01-02-08, 06:13 PM
#38
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I also have had some issues with the oil pan leakage, it took 4 new, stock pans for me to get it right. What worked for me was the right combo of hondabond, letting it semi-cure before i mated the surfaces and proper tourque on the bolts (both pan and motor mount). On the previous 3 something was missing, first i just slapped it together with the hondabond still wet (that flowed too much and caused gaps) Then I let it harden all the way and it wouldnt flex enough, finally i got it right the 4 th time. Its a PITA but once you figure it out it should hold for a while. sorry about the rambling run-on.
01-02-08, 07:54 PM
#39
Mine hasn't leaked so far, but I only did the job (with Permatex Ultra-Gray and no brace, but "dimpling" the pan - link: https://www.rx7club.com/showthread.p...easier+oil+pan ) about two years ago. So, IMO, the jury is still out on whether my fix w/o a brace is "permanent."
Dave
Dave
01-02-08, 08:25 PM
#40
Likewise, if you use a gasket, you're saying the bolts get left looser than if you use sealant only? Well no wonder you guys get leaks.
FWIW, tightening torque for oilpan fasteners is listed in the FSM. The root of the problem here is that all the small bolts get torqued to 104 inch-lbs, and then in the back all the sudden the motor mounts get torqued on at 68 foot-lbs. That means the torque in the back is 8 times higher than in the front. It also puts a lot more stress on the area between the last small bolt and the front of the motor mounts. Which is consequently where leaks always occur!
Whether you use a gasket or sealant, the motor mounts are constantly compressing and releasing, compressing and releasing, each time you apply and release throttle, shift gears, accelerate or decelerate, etc. Of course the seal is going to be broken loose eventually, it's a bad design.
Whether you use a gasket or sealant, the motor mounts are constantly compressing and releasing, compressing and releasing, each time you apply and release throttle, shift gears, accelerate or decelerate, etc. Of course the seal is going to be broken loose eventually, it's a bad design.
Regarding the compression/relaxation, that never happens with a properly torqued fastener. The engineering design is based upon separating forces, such that the total number of fasteners * the clamping force of each fastener > the maximum separating force seen in operation. The picture you paint would apply to hand-tightened bolts, not correctly torqued ones.
I feel that if you use a gasket you have a thicker medium there to absorb some of this motion and also the torque of each bolt, whereas with sealant alone, you simply wind up squeezing all your medium out the edges (inside and outside edge) and wind up with very little sealing material where it counts...on the pan flange.
Dave
01-02-08, 08:58 PM
#41
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So with that said, please point out what you feel is the issue with using a gasket (as a medium that will not squeeze out at pressure points) and sealant on each side (as a medium that better absorbs pressure points, according to you)? Sounds to me like you are arguing against the best of both worlds.
I still can't say that my line of thought, or my extensive experience (more than just a few oilpans) agrees with this, but I am just continuing the discussion until it's end.
I still can't say that my line of thought, or my extensive experience (more than just a few oilpans) agrees with this, but I am just continuing the discussion until it's end.
01-02-08, 10:35 PM
#42
The bolts should be the same tension regardless. The trouble with gaskets is that they require a perfectly continuous flat surface. They can't cover up a minute step between housings, for example, the way sealant can...... Sealant doesn't care about clamping pressure because it's squeezed out at the high points. The sealant carries zero pressure load. The gasket carries all of it.
Last edited by Sgtblue; 01-02-08 at 10:49 PM.
01-02-08, 10:51 PM
#43
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So with that said, please point out what you feel is the issue with using a gasket (as a medium that will not squeeze out at pressure points) and sealant on each side (as a medium that better absorbs pressure points, according to you)? Sounds to me like you are arguing against the best of both worlds.
I still can't say that my line of thought, or my extensive experience (more than just a few oilpans) agrees with this, but I am just continuing the discussion until it's end.
I still can't say that my line of thought, or my extensive experience (more than just a few oilpans) agrees with this, but I am just continuing the discussion until it's end.
Last edited by cp1; 01-02-08 at 10:58 PM.
01-03-08, 08:31 AM
#44
Racecar - Formula 2000
So with that said, please point out what you feel is the issue with using a gasket (as a medium that will not squeeze out at pressure points) and sealant on each side (as a medium that better absorbs pressure points, according to you)? Sounds to me like you are arguing against the best of both worlds.
Dave
01-03-08, 08:39 AM
#45
Racecar - Formula 2000
with my knowledge and experience ive described why using both gaskets is not recommended above. but then again to each thier own. and really if you are doing the work use whatever you think works but i would not allow a lot of peoples work to be done on my engine as it just isnt up to par.
In the case of sealant only, with the bolts torqued before it hardens, there is nothing to take a set at the high-load points, the bolts are locally fastening the pan to the block metal-to-metal (hopefully preventing slip), and the seal should last longer.
Dave
01-03-08, 12:37 PM
#46
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There will still be a thin film in all but the isolated most-heavily-compressed areas, which, in my, and others, experience, will seal very well. The alternative in these areas is to do it as you have said (leaving a significant sealant layer), and experience has shown that in this and similar applications, it will not work.
01-03-08, 01:12 PM
#48
Racecar - Formula 2000
In the motor mount area I put beads around the inner edge block surface (in the area where it contacts the pan) and around the bolt holes only to avoid too much excess.
Dave
Last edited by DaveW; 01-03-08 at 01:30 PM. Reason: Added link
01-03-08, 01:17 PM
#49
Racecar - Formula 2000
In the case of track or autocross useage (higher loads on the engine mounts), it should be especially useful.
Dave
Last edited by DaveW; 01-03-08 at 01:24 PM.
01-04-08, 08:44 AM
#50
Racecar - Formula 2000
I applied a regular (~3/16") bead (to the bottom of the engine as noted in the referenced "easier oil pan" thread - link: https://www.rx7club.com/showthread.p...easier+oil+pan ) so that the sealant would (a) be thick enough to contact both surfaces even with some irregularity, and (b) not be so much that it would squeeze too much out the sides and wind up breaking loose and clogging things.
In the motor mount area I put beads around the inner edge block surface (in the area where it contacts the pan) and around the bolt holes only to avoid too much excess.
Dave
In the motor mount area I put beads around the inner edge block surface (in the area where it contacts the pan) and around the bolt holes only to avoid too much excess.
Dave
Now that I think about it, in the motor mount area, I also applied a similar bead of sealant around the outer edge of the block, just inside where the small bolt holes are.
Dave
Last edited by DaveW; 01-04-08 at 08:51 AM.