Lotus Elan Central
Cam Oil Seal Repair

When I bought my Elan, the engine block and transmission housing were perfectly clean. After 10 months, both were coated with oil which looked very much like it was coming from a blown head gasket.

Cam oil seal image 1

After reading Bryn's write-up on the CAS cam seal, I could see that no oil was leaking from the CAS itself, so I looked for the bung as the source of the leak. Once I figured out what a bung is (a hole stopper per, it was a snap to find it hidden back behind the spark plug wires.

The bung is called the "Plug, inlet cam rear end seal" (Lotus part# A100E6294S) and the O-ring is called the "O-ring, rear cam cap plug" (Lotus part# A100E6562S). These parts are shown on page 269 and page 270 of the Parts Manual/Engine Section.

While the O-rings are available at Lotus or Isuzu (part# 8970757550), I bought mine to a local auto parts store where the old one was measured with a micrometer and matched up with a standard sized new one.

Its basically an easy repair - just pry off the old O-ring, clean up the bung and engine block, put on the new O-ring, slide the bung back in, and reattach bolts and wires. It took me a bit longer than the suggested 30 minutes to do the repair though because getting access to the side of the cam took some prep work.

cam oil seal image 2

Getting access to the bung was the first priority - its quite tight in there. I loosening up the oil separator, first taking the opportunity to open it and see what was inside - no oil but a couple separator plates. Then I disconnected all the spark plug and electrical wires in area. There are three sets of electrical wires to disconnect. Two of the sets are almost the same length and have connectors which are the same, so when disconnecting them make sure you label them - I didn't and had to play mix and match to get them back on correctly. One set attaches to the CAS near the thermostat housing and the other set goes to the coolant temperature sensor behind the CAS. The third set runs to the bottom of the CAS on the turbo side and is a much longer wire, so its easy to keep track of that one.

Once you get access, the repair is easy. The bung slid right out after the mounting bolt is removed. The bung is the black triangular shaped plastic part that has the circular extension off the side. The O-ring fits into a groove in the circular part of the bung. The old O-ring will be covered with crud, hardened with time and the engine heat and flattened into the groove, so its easy to mistake it as part of the bung itself. However, by working a sharp pick into the small groove slots you will be able to loosen it and pry it off. If you plan to buy the replacement O-ring at a parts store, be careful not to break or cut out the O-ring so that it can be measured and compared with a generic replacement. After replacing the O-ring, the bung will slide back into the cam cover and simply needs to be re-bolted in place.

After two weeks, not a drop of oil has leaked out, so $1.19 plus an hour of my time saved an expensive trip to the repair shop.

- write-up by Mark Alloy

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