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'84 300D, '78 300CD w/ '82 Turbo, '91 300TE (RIP), '88 260E 5 Spd (RIP), '98 E320 4 Matic (sold)
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Discussion Starter #1
Hello,
I have a 1988 260 E. It burns about a quart of oil a week, but only produces smoke when the temp gauge is over 80 (which is stop and go traffic or if I drive for 20 or more minutes and then get stuck at a light). I just replaced the valve stem seals and spark plugs with no change. I have bought a head gasket set and valve guides as my next strategy, but I haven't a clue how to replace either. Is a temp over 80 over heating? If so, would that cause the smoking?

Cheers,
Werner J Stiegler
 

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About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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5,466 Posts
How many miles on the car? If it's less than 250k the bottom end should be fine unless the car was poorly maintained or horribly overheated.
I'm surprised that the vlave stem seals didn't fix the oil consumption problem -- that did the trick on my 88 260E. What tdid the old spark plugs look like?
The thermostat should be an 87C part so expect the temp gauge to read just over 80 almost all the time unless the ambient temp is high and you're running the a/c. Then you may see 100C until the aux fan kicks in.
If you're not an experienced DIYer you don't want to tackle a head gasket replacement. It's a big job, you need a fair assortment of tools, and you should have a fair amount of experience to go there.
As for valve guides, well, that's a job for a machine shop. The head has to be removed, stripped, and the old guides pressed out and the new guides pressed in. Then you need a valve job to get the valves to seal properly. This is not a DIY job.
Are you losing transmission fluid?
Smoky exhaust can come from a ruptured transmission vacuum modulator which allows transmission fluid to sucked into the engine.
 

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2008 E350 4M, 2016 Audi Allroad, 2019 Audi Q5
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5,446 Posts
If your new plugs are still getting the black oil deposits on them, then the valve guides are done for. The valve stem seals are bandaid fixes for worn valve guides. For most people, it fixes the consumption, or makes a drastic difference.

Also, are you sure you didn't get the intake and exhaust seals mixed up?

If you are doing the head gasket, take the guides and seals with the rockers + cam removed to a machine shop. Have them skim the head, clean and pressure test it. Then replace the guides. Should run you ~$250.
Check out mine here:
Head Gasket Replacement at W124-Zone.com – A Mercedes W124 Resource Site
 

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'84 300D, '78 300CD w/ '82 Turbo, '91 300TE (RIP), '88 260E 5 Spd (RIP), '98 E320 4 Matic (sold)
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221 Posts
Discussion Starter #4
Hello,
Very possible that I got the exhaust and inlet mixed up. Could be bad.
Cheers,
Werner J Stiegler
 
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