Valve Cover gasket (‘75 Eldorado)

[benji808]

In the almost two years I've the had the Eldorado, I've replaced valve cover gaskets 3x (twice myself, and once by the shop that did the engine rebuild). One or both have started leaking each time. I'm looking at trying again...any tips? Anyone else had a similar issue? It seems like a really simple job, so I'm not sure what the issue is.

I'm aware to not overtorque, and spend quite a bit of time cleaning the surfaces so they are smooth. Only gaskets I was able to find are the cork ones. I don't use any gasket maker/sealant.

["Cadillac Kid" Greg Surfas 15364]

Benjamin
The most likely cause is that the covers are not straight  (at the gasket surfaces of course). Pull the covers and lay a straight edge along the gasket channel. Previous over tightening is usually the culprit and you will find imperfections around the bolt holes. These are typically easily straightened with a small hammer or even better a body dolly (do you old timers remember these?) against a solid flat surface like the edge of a 2 by 4 under the cover's edges. I typically use something like weather strip adhesive to "glue" the gaskets to the cover and the other side is left dry.
Greg Surfas

[smokuspollutus]

Cast aluminum covers with rubber gaskets are the best. But if you value originality/don't want to spend a lot sourcing them for a big block Cadillac, you can read up on what I did to create a rubber gaskets for use with stamped parts (although not shown, I did my valve covers under the same premise and have no leaks)  I used a skim coat of RTV to "glue" the rubber gaskets to the covers to keep them in place during install.  This is on a 4100 which is a substantially more difficult seal to create.

This of course assumes the above is true and the cover is not deformed and you've already done your best to straighten the bolt holes.

Load spreaders are not a bad idea if working with old stuff that has been overtightened. If the covers have been off so many times already, they are definitely more than a little dimpled. The little triangular ones are thin enough to allow you to use the original bolts and wide enough to give you that little bit extra load spread to keep the hole from blowing back out as you tighten down. They can be painted and be next to invisible.

The name of the game is clamping area. Older engines are limited in that the bolt heads are small (at least Cadillac used 8 bolts, Chevy used 4!) and the sealing area itself is pretty thin. Couple that with stamped covers and cork gaskets...it can be challenging to get a lasting seal. However, in addition to the 8 bolts, Cadillac V8s of this time send comparatively little oil to the heads, so it should not be impossible to achieve in the modern day.

Make sure your oil return holes are unrestricted and their is minimal/no standing oil in the head. On an Eldo, there should be no oil laying in the heads with the car parked level. If the return holes are restricted, nothing you do will stop the leak short of cleaning the holes out.

https://forums.aaca.org/topic/368159-make-your-own-rubber-oil-pan-gasket/

[walt chomosh #23510]

Ben....been there numerous times....that is, until I started using the "right stuff". After fighting valve cover leaks for years, a friend who ran a machine shop (VERY high level) told me about this Permatex product. Practically all auto parts houses stock it. I attempted to seal leaking Harley Davidson rocker covers on a vintage Panhead, over and over again until I learned about the "right stuff".Try it, you'll agree it is "game over"!...let me know how you make out......walt...tulsa,ok

[Cape Cod Fleetwood]

Permatex makes GREAT products, many on The Ark. And a friend is on the alky pit crew, transmission.

[TJ Hopland]

Like some others have mentioned the first thing I would be doing is making sure the covers are straight.   When installing them with cork gaskets like others have said some proper sealer to 'glue' them to the covers is a good idea.  And we are not talking about a 'bead' of sealer here, just a film usually applied to the gasket side.  Also use a torque wrench to make sure you are not over tightening them and causing the covers you may have just fixed to warp again.

I would think someone still makes rubber gaskets for these but I would not use rubber with the stock 'tin' covers.  I don't think the stock covers are stiff enough to put enough pressure on rubber to properly seal.  IF you have cast covers you can use the rubber gaskets.

He did mention the engine is rebuilt so there should not be a drain back or excessive blow by issue but those are good thoughts when dealing with oil leaks.  I guess it would be worth asking does this engine still have the stock or other breather in one valve cover then the PCV in the other?   If something different was done maybe trying to return it closer to stock would be worth a try.

Also on the subject of PCV and breather is the air compressor still working or disconnected and capped?   The vacuum source for that was the PCV line.  Maybe if the compressor has failed or didn't get properly removed its got a vacuum leak and the PCV isn't getting enough vacuum to work so there is too much crank case pressure and that is whats causing oil to try and escape from otherwise reasonably sealed areas?   A clue to that maybe happening would be oil residue near the breather and finding the dipstick not fully seated in its tube.

[TJ Hopland]

Oh and the other thing to add is you want to use the stock style bolts that have the built in tooth washer sort of things.  A regular bolt and washer never seems to want to stay tight, not sure if that is due to vibration or the heat cool cycles or both.

[benji808]

Thanks everyone for the thoughts and advice!