Roy's Garage: '90 2.4-4G64 5-spd D-50

[royster]

MY D-50 STORY
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What I learned, just up to this point, might help someone else NOT make the same mistakes I (and others) made. Life is like that: we can learn from others, or learn from hard knocks. "Experience is the best teacher", and this is so true. You can read from 100 books, but until you experience in real-time, you don't know much.

Varying degrees of smoke would emerge from the exhaust system when I started up my "new" truck. It didn't happen when the motor was warmed up, only after sitting for periods of time. What I didn't know then was what this was a clear symptom of: worn valve stem seals. There is a fairly easy repair for this problem (a thread HERE discusses it) that gives good results. But I didn't know at the time. I figured loading the motor with the thickest oil I could find would buy me some time. It likely caused the timing belt to strip. I ran pure Lucas Stop-Smoke oil, which is okay at operating temperatures, but gets so thick and "slow" at cold temperatures, it probably can't get through oil filters or passageways. And what I have to share is: thick oil doesn't permanently fix the problem. Replacing the valve stem seals DOES.

What I suspect happened is that the cold temperatures (40-30 degrees F) made turning the cam shaft hard, and at some point this stress caused the timing belt to strip. There might be another bearing issue on the head, and I won't know until I get the valve cover off. I did get the full timing cover off, and the secondary belt is fine. The belts were actually in very good shape when I bought the vehicle. My own "old thinking" (from conventional, American-made motors) essentially killed the D-50...for now.

But the experience pushed me to look into these trucks and engines with full focus...no half-measures...and it ultimately brought me to this forum.

If you're living in a cold climate area and have put thick oil in your D-50 or Mighty Max, take the time to pour a can of SeaFoam into the crank and thin out the oil, pronto. Let it run for a bit, then change the oil. Run pure 30 weight, but don't put STP or oil thickeners in there. Your smoking problem is more likely these seals than it is the rings.

Another valuable tip I learned from the community here is that the hard-starting of my D-50 was likely a bad water-temperature sensor. I wondered why the choke didn't seem to be working, and quite frankly, I wasn't sure if my D-50 had a carborator or was fuel injected. So live and learn. My "conventional" mechanical experience didn't help me to understand the 4G64, other than basics. It's a whole different ball-game than a slant six 225. Vehicles with timing chains can endure the stress: timing belts will only take so much before they file for divorce and demand custody of the glazed-donut locker.