sealing sump

[TXWRX]

have got a ford x-flow in our kitcar which is all built up and ready to go, problem is we keep getting a small weep from the edge of the sump. Had to take the sump off and i reckon the issue is simply not putting on enough gasket seal but just how much do people tend to use? i've got another x-flow which was put together by an engine builder and externally it looks like he's used loads of the stuff, leaks tend to come from the rubber seals at each end of the engine

[Pumaracing]

First thing to get right is what sealant you use. Ordinary clear DIY bathroom silicone like this

http://www.amazon.co.uk/dp/B001GU6CQ4/ref=asc_df_B...

will do just fine and that's what I've used as a professional engine builder for over 20 years although you can buy special automotive RTV silicone at several times the price.

For cars with catalytic converters, which clearly yours isn't, you don't want silicone that releases acetic acid when it cures although this will still be fine if you leave it long enough before starting the engine and potentially contaminating the cat.

You want a thin smear of this between the gasket and block and a bead about 3mm in diameter between the gasket and the sump. I always run the bead down the middle of the bolt hole line between each bolt hole and go round the outside of each bolt hole rather than the inside. This means any excess tends to squeeze out rather than in. Alternatively you can just use your finger to apply a layer of sealant about 0.25mm thick all round the flange concentrating it mainly on the outside 3/4 of the flange thickness so again it doesn't squeeze inside the block too much.

Then nip the sump bolts up finger tight with a small spanner and leave the sealant to set for 24 hours before tightening fully. You should see a small bead of sealant about 2mm in diameter all round the outside of the flange if you've applied the right amount.

Provided the surfaces are clean and dry before applying it silicone sealant is pretty much bomb proof once it's cured and I've never had a leaking sump since using it.

[TXWRX]

Right, thats certainally different from how we've done it but makes a lot of sense, thanks for the advice

[Pumaracing]

Let us know how you get on once you've refitted the sump.

[TXWRX]

will do, if the weather holds out should run the car again early november, pic of it in its current state and how it should look with its new wheels fitted (though the wheels probably won't have the blue stripe featured) :

[TXWRX]

Digging this thread up a bit, but with an answer that yes the sump sealing method has worked perfectly! car is now on the road as per this thread http://www.pistonheads.com/gassing/topic.asp?h=0&a... and not had any more signs of oil leaking so thanks

[westwood35]

We had a similar problem with my formula ford. We now use the gasket sealant that Honda use on their engines, where they have no sump gasket. Works really well.

[Pumaracing]

TXWRX said:

Digging this thread up a bit, but with an answer that yes the sump sealing method has worked perfectly!

Thanks for the update. Glad to be have been able to help.

[rev-erend]

I'm now an rtv silicon convert .. fantastic stuff.

[Simon says]

rev-erend said:

I'm now an rtv silicon convert .. fantastic stuff.

In moderation and used correctly its wonderful stuff

[rev-erend]

Simon says said:

rev-erend said:

I'm now an rtv silicon convert .. fantastic stuff.

In moderation and used correctly its wonderful stuff

Very true .. put it on, leave it for 5 mins, work it into areas to cover then place items together. Job done.

[DVandrews]

Be circumspect in the amount that you use, it is also very very good at blocking up oil pickup pipes.

I never use it where it could get inside the engine cavity for that very reason, I have seen many engines with pickups partially or near completely blocked by great gobs of excess RTV sealant that have extruded inside the engine and broken off.

Dave

[PaulKemp]

I have that particular Tshirt, bought an engine which subsequently had oil pressure problems, took it apart to find pickup strainer full of gunk, and the gunk got everywhere, a heavy hand was used when that engine was built, I now am also sparing with sealant.

[Pumaracing]

As always common sense needs to prevail. Garage mechanics can slap silicone on like cake icing and cause all sorts of problems but applied as I suggest and leaving only a small 2mm bead round the flange after tightening, silicone never breaks off into the engine in use. In fact it take a fair pull to remove it all when you strip the engine down.