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Re: Replace the gasket Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Fri, 23 May 2008 12:36:27
In Reply to: Re: Replace the gasket, Collin, Fri, 23 May 2008 08:34:39 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I'd replace the gasket. There's a good chance it'll get damaged in the process. Also, you'll never clean the old sealant and oil off it well enough for the new stuff to adhere. Gaskets are cheap. Or, cheap, compared to doing it yet again.
I want to be clear on the nomenclature of various Goops. RTV actually stands for Room Temperature Vulcanizing, and covers a broad range of materials that set at room temperature. They can be rubber, Silicone, or other materials. There are many RTVs, and many are totally wrong for this application. Many RTV require air to cure, so they make for a lousy surface mating sealant. Others contain corrosive chemicals - just about any RTV that smells bad contains acids.
Loctite makes lots of different chemicals. There is something called Gasket Cement. The purpose of gasket cement is to hold a gasket in place during assembly. It provides little if any sealing capability - the gasket should provide that. Gasket cement is good for blind assemblies or where you need to put something together upside down and you don't want the gasket to fall off.
Loctite 518 is a 'Flange Sealant', designed for flanged mating surfaces. It is also anaerobic, meaning that it cures without air. It can actually be used instead of a gasket if the mating surfaces mate really well. It doesn't fill large voids very well.
For the valve cover, the rubber gasket fills the big void, but you still want a sealant to seal the thin surface between the head and the gasket, and the gasket and the valve cover. For that an anaerobic oil resistant non-corrosive sealant compatible with steel and aluminum. Form-a-gasket works, as do many gasket sealants. I like the Loctite 518 for the job.
Scanwest probably did a fine job, but maybe the mechanic was having a bad day and didn't put enough sealant on at the distributor hole. It's also tricky there, and it's possible the gasket got pinched or displaced. Stuff happens.
A torque wrench would be nice. Note that a really nice to have torque wrench usually starts at about 20 ft-lbs and goes up to 150 ft-lbs. So the one you'd really want won't work. Those are the 'click' type (they go 'click' when you reach the right torque.)
A useful tool for small torquing jobs is also quite cheap. Pep Boys and most autoparts stores will sell a cheap 'beam' type torque wrench.
See http://en.wikipedia.org/wiki/Torque_wrench, and look to the left where it says "beam type".
Beam types have a few disadvantages - they require reading, and they usually don't ratchet. They are nice because they are cheap, and for low torques, pretty good. They typically come in inch-pounds or You need 11 ft-lbs, which is 12*11 = 132 inch-pounds. You can probably pick up a 300 inch-pound beam type wrench for $15.
I'd recommend the wrench, because an easy way to guarantee a valve cover gasket leak is to over- or under-torque the bolts.
If you really don't want to buy the wrench, you need to apply the right force to a known length. For example, if you have a 8" rachet handle, you need to apply 16.5 pounds at the end to get 11 ft-lbs. Does it have to be 16.5 +/- 0.5? No, a couple of pounds either way is just fine. But can you estimate 16 pounds? Not easy. If you've got a fish scale, you could try pulling on that on the end of a wrench. Or buy a torque wrench. They come in handy.
When you tighten the bolts, DON'T start at one end and work your way around. That will cause uneven tightening. Screw the bolts down finger tight, then pick a corner and tighten one bolt down about half torque. (Say upper right) Now go to the opposite (diagonal)corner (lower left) and do the same. Now go to the lower right bolt, then upper left. Now, go to the one next to the one you started with, and keep up the pattern. It's not super critical, but you want to avoid tightening two bolts next to each other. After they're all about half-tight, bring them all to full tight with about the same pattern. This is really critical with head bolts, not as critical but good on a large floppy surface like a valve cover or oil pan.
posted by 192.249....
, Thu, 22 May 2008 20:50:50, Fri, 23 May 2008 12:36:27 <-- Viewing This Message, Fri, 23 May 2008 05:04:18
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