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Old 11-04-2017, 03:17 PM   #1
lummert
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Default B230FT Boost and Blow-by Connection

Been having an issue with my 88 765 Turbo wagon. K-Block B230FT (294K miles). 90 manifold with TD04H-13C which appears to be a late model low pressure turbo. I placed thick washer for each bolt between compressor housing and wastegate actuator. It seems that everything is fine until getting into boost while passing slow cars on 55 mph 2 lane highway (going as fast as 85 mph while passing). The next time I park the car I notice oil on the tip of the tail pipe. The engine is old enough to smoke and does it fair share. Most likely the intake valve seals are leaking oil.

Vacuum/pressure test gauge was pegging the needle indicating 7 psi while in boost. The gauge has a stop pin at 7 psi. I removed the thick washers and installed thin washer for each actuator mounting bolt. Test gauge still indicates between 6 and 7 psi while in boost.

My theory is that the high mileage engine running at more than stock boost is causing excessive blow-by while in boost.
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Old 11-04-2017, 03:39 PM   #2
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A friend used to have an 88 760 turbo K block sedan and it used to blow the dipstick out at sustained full boost. Stock boost. I replaced the breather box, all the pcv stuff and made sure the oil drain from the breather box was clear. This engine never used synthetic oil. Had about 180k miles on it. After all that it still blew out the dipstick during full boost. We settled on worn but still running ok at that point. He eventually got something else. If it was my car I would have vented the valve cover to try and help the situation. Maybe that may help yours?
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Old 11-04-2017, 03:44 PM   #3
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A friend used to have an 88 760 turbo K block sedan and it used to blow the dipstick out at sustained full boost. Stock boost. I replaced the breather box, all the pcv stuff and made sure the oil drain from the breather box was clear. This engine never used synthetic oil. Had about 180k miles on it. After all that it still blew out the dipstick during full boost. We settled on worn but still running ok at that point. He eventually got something else. If it was my car I would have vented the valve cover to try and help the situation. Maybe that may help yours?
I have considered venting the valve cover. I have already fabbed up a catch can, so running another hose to the catch can is not that big of a problem.
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Old 11-04-2017, 03:45 PM   #4
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Dammit lummert... at 300k miles she probably pees from every orifice. Blow-by, valves, turrrrbo seals...

F'k it, be happy. Keep an eye on the dipstick.

What oil are you running?
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Old 11-04-2017, 04:00 PM   #5
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I recently vented the valve cover in my 93 wagon. I went to do a breather box replacement and the oil trap return hose was completely clogged. I tried to clean with hanger wire going through it but it only seemed to help a little. So I vented the valve cover by getting a B18B oil filler cap and pcv hose. Then Ting that into the pcv hose that goes to the intake plastic pipe near the throttle body. This is a B230F with 413k miles.
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Old 11-04-2017, 10:54 PM   #6
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Do a leak down test to verify the condition of the engine is where I would start then makes sure there are no blockages anywhere causing the blow by.
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Old 11-13-2017, 05:20 PM   #7
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Would a boost leak cause my 765's excessively rich running at highway speed, but not around town? I found the hose that runs into the intercooler has a very weak spot due to oil damage. There is a sign of oil blowing out of that spot onto the turbo inlet hose just below.

I replaced the end nearest the turbo outlet with a 45 degree 2 inch hose and a short length of 2-1/8 inch tube. This fixed the boost leak at least until the other end of the hoses goes bad. In my area a new boost hose would require online ordering and shipping costs. I have already replaced all of the other boost hoses which were oil damaged.

Fixing this boost leak resulted in having to adjust the AMM POT screw at least 3 turns CCW (leaner) to get the LED test tool to blink.

Last edited by lummert; 11-29-2017 at 03:28 PM.. Reason: Update
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Old 11-29-2017, 07:02 PM   #8
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Bump for update:
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