91 c4 base
Race Director
Joined: Mar 2017
Posts: 11,949
Likes: 4,507
From: Virginia
The safest thing to do would be to sell your C4 immediately, and buy a C3 instead.
EDIT: Did this thread get moved to C4 Tech (from C3)? Well, I stand by my advice. And pictures always help!
EDIT: Did this thread get moved to C4 Tech (from C3)? Well, I stand by my advice. And pictures always help!
Last edited by Bikespace; Apr 6, 2026 at 04:39 PM.
Oil Producer
Joined: Apr 2014
Posts: 9,371
Likes: 2,736
Hi, if it is at the base of the distributor where it sits on the manifold, yes there is a circular paper ring gasket. If its leaking from there it would odd for it to more than just a very very limited weep.
If the leak is below the distributor and drizzling down the back of the block then chances are that it is a failed “rear china wall” leak. Very VERY common but also very easy to rectify with tools and the patience to do the job.
Of note, other things in that vicinity that could leak oil:
- oil pressure sensor sending unit AND its threads into the blocks port.
- the rear intake manifold to block gasket.
Try posting a pic and we might be able to further help. Cheers.
If the leak is below the distributor and drizzling down the back of the block then chances are that it is a failed “rear china wall” leak. Very VERY common but also very easy to rectify with tools and the patience to do the job.
Of note, other things in that vicinity that could leak oil:
- oil pressure sensor sending unit AND its threads into the blocks port.
- the rear intake manifold to block gasket.
Try posting a pic and we might be able to further help. Cheers.
Racer
Joined: Feb 2024
Posts: 268
Likes: 113
From: New York
VERY common for these to leak. There's an oil pressure sending unit for the gauge and an oil pressure switch back there. The oil under these units is pressurized while the engine is running and they will leak internally. When they do, oil comes out through the electrical plug. Unplug each and if the plug is wet with oil, replace the unit.
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