Question about exhaust valve leakage
09-17-2018, 08:31 AM
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240D
Question about exhaust valve leakage
I've got a 79 240D that has low compression. 220-300 psi cold tested. Even the best cylinder shows 100% leakage through exhaust valve. Valves have been adjusted and timing chain shows no stretch.
Is it usually valve seats that's the problem in this situation, or are valve springs or guides a common issue? I don't have any experience in this area. Car has only 130,000 miles.
Is it usually valve seats that's the problem in this situation, or are valve springs or guides a common issue? I don't have any experience in this area. Car has only 130,000 miles.
09-17-2018, 05:57 PM
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W123 300CD, R107 560SL, W211 E320
I would get a second opinion on the valve adjustment. Did you do it yourself? If a shop did it, check it again. preferably at a different shop. Such problems at your mileage are rare.
09-18-2018, 04:28 AM
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I did the valve adjustment myself right after I bought the car about a month ago. Checked the clearances again when I did the leak down test and the clearances are right. At TDC each exhaust rocker has a little play in it but the valves still leak air. Figured it was unusual for a relatively low milage diesel but that's what it does.
11-14-2018, 06:27 PM
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240D's have valve issues that *may* e more age than mileage related .
Assume when you adjusted the valves most were tight ? .
If so, drive it hard for a few hundred miles then check/adjust them again as necessary, remembering it needs to be done engine STONE COLD .
An engine that hasn't had the valves adjusted for too long sometimes builds carbon up on the valves & seats, running it hard breaks that up and removes it, allowing the valves to close properly, why you'll need to re check and adjust the valve once or thrice before they hold adjustment for 10,000miles like they should .
@ 300# per cylinder it'll still start and run O.K. but you will find it useful to wait until the seat belt lamp goes out instead of cranking right after the glow plug light goes out .
Assume when you adjusted the valves most were tight ? .
If so, drive it hard for a few hundred miles then check/adjust them again as necessary, remembering it needs to be done engine STONE COLD .
An engine that hasn't had the valves adjusted for too long sometimes builds carbon up on the valves & seats, running it hard breaks that up and removes it, allowing the valves to close properly, why you'll need to re check and adjust the valve once or thrice before they hold adjustment for 10,000miles like they should .
@ 300# per cylinder it'll still start and run O.K. but you will find it useful to wait until the seat belt lamp goes out instead of cranking right after the glow plug light goes out .
