Got a funny noise...broken precup? (1 Viewer)

[GTSSportCoupe]

I've got a strange noise that I'm having quite a bit of difficulty locating. It's been getting gradually worse the last few months. It only happens on cold start-up, when the engine is warm it's gone. Also, on startup, if I raise the idle to 1200rpm or so, the noise goes away instantly (even when engine returned to normal idle it's gone).

I've eliminated (I think?) all sorts of things like belts, idlers, fan. I think the noise might be from inside the motor, but it is very hard to locate.

I'm beginning to wonder if it's possible one of my pre-cups has cracked through and bounces around a bit until it warms up (expands).

Anyone know what a broken precup might sound like? Link to a video?

When I start my motor tomorrow, I'll take a video and post it to youtube.

The engine starts and runs absolutely perfectly otherwise.

 

[stevebradford]

I do unfortunately sounds nasty tick like valves need adjustment real bad but only at certain rpm.

if there’s a chunk in the cylinder it can be a super nasty intermittent hammering.

I would pull the injectors and fish around to find out what you can as much as possible before this happens. I hope it’s not!

 

[GTSSportCoupe]

Thanks @stevebradford. I'm probably thinking worst case scenario here; but better that I check just in case!

 

[gerg]

I've been able to fit a borescope through the injector hole in my 3B to inspect precups before. Not sure if that is possible for you but you could measure the opening if you pull the injector. I think my scope was 5.5mm. Hammering pre cups can do terrible damage even if they aren't broken. If you were able to put a small hook through the glow plug hole and hook the precup opening and pull on it and put a small rod through the injector hole I bet you could tell by alternately pulling and pushing on the cup if it was able to wiggle. Short of pulling the head I'm not sure how else to assess for a lose cup.
Have you been able to isolate it to a cylinder?

 

[cruiserpilot]

Do you have a stethoscope?

 

[GTSSportCoupe]

Do you have a stethoscope?

Yes. The biggest problem is just finding time to work on it. And this noise in particular is hard to catch, as it's only there for a short while. There is definitely a possibility it's still something simple. Poking around more with the stethoscope is a dang good idea.

Thanks everyone for your input. Hoping it's not a precup coming apart, but was curious as to anyone's experience with this (thanks Steve and Greg for your thoughts on that). I'll let you know how I make out.

If it is a precup and it's damaged the piston, it might be 15BFT swap time! If it's just the precup I might try the 2LTHE head with the ceramic precups. Or maybe part the truck and move on.

 

[AussieHJCruza]

I vote for 15B-FT swap - no such thing as too much power

 

[GTSSportCoupe]

OK, fired it up this morning at ~0C engine temp. Noise was very prominent and I got a video of it. I followed @cruiserpilot 's advice and poked around some with a stethoscope. I listened at each injector (right above precup), and the noise is DEFINITELY not a precup issue. I poked all around the cylinder head and it's not from the valve train either. Should have done this before posting about broken precups....

Despite having replaced every accessory belt/idler the alternator/vac pump, crankpully, A/C compressor, waterpump, timing belt/idler, viscous fan clutch in the last couple years, I'm back to thinking the noise is still coming from that area somewhere. Possibly these north american belts I've recently crossed to might actually be causing this noise. Will play around with the tension (I think they're fine, but will try more), and see if the noise changes.

I vote for 15B-FT swap - no such thing as too much power

They fit really well in Prado's. Given the towing etc. I do, it would be the perfect motor. And they seem to be coming up cheaper than 1HD's etc. anyhow! Love the idea of a light duty 70 series with a megacruiser heart, haha.

 

[GTSSportCoupe]

Couple vids. First is initial start-up (~0C, not plugged in, first start of the day). Second is a few seconds later - noise is more prominent. Something at the front of the motor I think. Not your typical belt/tensioner/bearing noise issue though...

 

[gerg]

Well not sure what it is but I'm happy it's not a pre cup!

 

[Mr Cimarron]

When my B broke a precup it sounded like a knock. It ran fine and a few times when I moved the truck around the noise went away. When I pulled the head there were two small fragments of the precup that I assume were making the noise when they were getting slammed between piston and head.

 

[GTSSportCoupe]

Somehow I found some more time this weekend and did a bit of wrenching. Changed my oil and it had no impact on the noise (good!). Tightened those new belts I installed a couple months ago, and voila, the noise is virtually gone. Looking closer in that area before I worked on them I could see they were bouncing around quite a bit; which I think may have been causing that strange noise (despite the tension having been pretty good). Anyhow, I think I'm going to go back to a proper OEM belt replacement part number. I think maybe these belts are a touch wide, and sitting too far out in the pulley groove, thus causing this weird resonance issue.

Thanks all! Glad it's nothing major. What a strange noise though; and hard to locate.

 

[John in Utah]

My 3L makes some strange noises when cold, and they definitely don’t sound like internal engine noise. I have some oem belts waiting to go on - Here’s hoping that’s my issue as well.