Start up rattle - observation
- Thread starter PDoyle
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The blue fan clutch comes from the factory with 3,000 cst oil. What I've done is to advance the timing of the clutch and upped the viscosity of the oil to 6,000 cst. This yields better cooling. I'm recording MPG numbers now that it has gotten cold to see it's impact.
That's pretty interesting...so you're suggesting that the infamous startup rattle is associated with the fan clutch and not some squirrelly oil passage/pressure stuff. Is this the ONLY change to have been done between rattle and no-rattle?
I think I could be a believer...
I've never understood the theory of the oil aspect of this, but it's easier for me to understand how this could be causing that noise. Any chance of you putting the old one on to see if you can reproduce the noise?
I think I could be a believer...
I've never understood the theory of the oil aspect of this, but it's easier for me to understand how this could be causing that noise. Any chance of you putting the old one on to see if you can reproduce the noise?
PDoyle- are you sure the louder startup roar from the modded fan clutch isn't masking the startup rattle? IIRC the rattle was attributed to the timing chain, so I don't see how the new fan clutch would affect it.
Wow, you're the 2nd person this week to report that.
https://forum.ih8mud.com/showthread.php?t=122754
My start up rattle disappeared after replacing the fan clutch but so many things were done at the same time I never considered the clutch. It was replaced at the same time as the HG (pm) along with a bunch of other stuff including cleaning the throttle body. I had assumed it went away because the throttle body was clean and I no longer got the high start up RPMs.
I can vouch that the start up rattle is most definitely not the fan. As I don't have a mechanical fan.
But did you ever have the rattle or do you still/now have it?
Me and Pat talked about this at dinner last week. I don't think the fan clutch directly stopped his rattle.
He has a truck with a stock temp gauge, so elevations in operating temps will go unnoticed. One thing I can say for sure is that when the engine is operating at normal (around 185*) temps the oil pressure will read higher than when the engine in running hotter.
My startup rattle was resolved with a valve shim service. The day before I had it and since then it has never returned.
My personal opinion is that the rattle is form the valves and the new fan clutch is better maintaining his engine temps which is not thinning the oil quite as much after driving and is leaving a better coating behind for the next start up.
He has a truck with a stock temp gauge, so elevations in operating temps will go unnoticed. One thing I can say for sure is that when the engine is operating at normal (around 185*) temps the oil pressure will read higher than when the engine in running hotter.
My startup rattle was resolved with a valve shim service. The day before I had it and since then it has never returned.
My personal opinion is that the rattle is form the valves and the new fan clutch is better maintaining his engine temps which is not thinning the oil quite as much after driving and is leaving a better coating behind for the next start up.
- Thread starter
- #11
I waited about 3 months to post this (observation) because I wanted to make sure there was no more start up rattle. Rick would know better than I why there is no rattle. But, I'm absolutely sure the rattle has diminished after the clutch fan install.
Sadly, I still have and have always had the rattle. I have found that the best thing I can do is get the idle down as fast as possible when starting cold. Putting the trans in "L" or "R" keeps the revs below 1k instead of nearly 2k. My rattle doesn't go away any faster regardless of what I do, but if it take 30 seconds to go away whether it is turning at 1 or 2k I have effectively cut the unlubricated revs in half.