Knock at Cold Start for a few minutes (1 Viewer)

[ryyount]

Been getting my 60 up to running condition, and lately I've noticed in the mornings when I go to start it (ambient temp around 40F most days), I get a somewhat subtle knock as it warms. It only does this once in the day, and it's usually gone by the time I'm ready to pull out of the driveway after warming the truck for a minute or two. Any other start throughout the day it doesnt return. I dont think it's belt related, though I am going to replace them with new belts currently on order from Toyota.

After reading a few threads on the matter, people suggested to pull spark plug wires one at a time - didnt make any difference until I got to plug #6. It quieted a bit, but didn't totally go away. I've adjusted the valves twice in the last week (still getting the hang of doing it before it cools down). Engine is desmogged and I've advanced the timing to around 10*. Stock carb, stock dizzy.

All that to ask, am I in trouble with this issue? Oil pressure looks good (about halfway to 2/3 up the gauge most of the time). I've freshly changed the oil to a 15w50 synthetic with a toyota filter.

 

[Rgill]

Since the sound does change, I would drop the pan and look at the rod bearings. Possible that can be saved before it really gets bad. How many miles are on it?

 

[ryyount]

Since the sound does change, I would drop the pan and look at the rod bearings. Possible that can be saved before it really gets bad. How many miles are on it?

181k. The confusing part is that it goes away once warm.. Do I have more of an oiling problem than anything else?

 

[Rgill]

181k. The confusing part is that it goes away once warm.. Do I have more of an oiling problem than anything else?

I would not think so if the oil pressure is good. Once everything warms up and the tolerances close up may be why it goes away. May not be a rod, might also be a sticky lifter, etc. Might try a stethoscope and see if you can pinpoint where it is coming from. Open the oil fill port and listen to the valves. Put your scope on the oil pan next to each rod location and see if it coming from that area.

 

[OSS]

My FJ60 had an idle knock at first startup when it was only 2 years old in 1988 with 42K mikes in it. It never amounted to anything - 285,000 miles later.
I think when the engine isn’t idling perfectly smoothly something bangs a little bit due to big thrust clearances.
At least that was my conclusion on my engine.
I know that if one cylinder has low compression, the engine can definitely make a rhythmic knocking sound at idle.

 

[ryyount]

My FJ60 had an idle knock at first startup when it was only 2 years old in 1988 with 42K mikes in it. It never amounted to anything - 285,000 miles later.
I think when the engine isn’t idling perfectly smoothly something bangs a little bit due to big thrust clearances.
At least that was my conclusion on my engine.
I know that if one cylinder has low compression, the engine can definitely make a rhythmic knocking sound at idle.

Interesting. I do have a wobbling belt on the alternator. Looks like most of the pulleys are rolling straight, the belt is just warped from sitting forever. Going to replace those here in a few days. Had also wondered if I’ve got a clogged cat. The exhaust pressure from the tailpipe is pretty mild, might be worth looking into?

 

[OSS]

I’d start off with giving the engine a full tune up as described in the 2F manual- and not skipping any of the steps.
The 2F literally talks to you when it wants a tune up. Things are much smoother when everything is running as it should.

 

[ryyount]

I’d start off with giving the engine a full tune up as described in the 2F manual- and not skipping any of the steps.
The 2F literally talks to you when it wants a tune up. Things are much smoother when everything is running as it should.

I have done a full Desmog, manifold gaskets, carb rebuild, valve adjustment, timing, rotor, cap and wires with new gapped plugs. Fresh fuel tank with a clean filter. New charcoal canister.

Any chance this would be a result of too far advanced timing? I’m right at 10* and no HAC.

 

[whitey45]

A true rod knock will knock when you increase the rpm, the knock will follow the increase in rpm. If the noise went away or was less noticeable when disconnecting #6 its most likely rod clearance. When it warms up, things expand and clearance gets better. I would pull the pan and check all the rods for movement. I had a rod bearing spin as I revved it up!! It started to knock bad! Shut it down, pulled the offending rod bearing cap, polished the crank and fit a new rod bearing, ran great for another 50k!!!

 

[ryyount]

A true rod knock will knock when you increase the rpm, the knock will follow the increase in rpm. If the noise went away or was less noticeable when disconnecting #6 its most likely rod clearance. When it warms up, things expand and clearance gets better. I would pull the pan and check all the rods for movement. I had a rod bearing spin as I revved it up!! It started to knock bad! Shut it down, pulled the offending rod bearing cap, polished the crank and fit a new rod bearing, ran great for another 50k!!!

Here’s my (warmed) compression test numbers from today…

1: 170
2: 165
3: 163
4: 163
5: 165
6: 175

Does this tell you anything that cyl 6 is much higher than all the others?

 

[whitey45]

Compression has nothing to do with rod bearing clearance

 

[OSS]

Compression has nothing to do with rod bearing clearance

True, but if one cylinder is low, the engine will idle rough which will cause things to bang together- knock. I witnessed it first hand.

 

[OSS]

Here’s my (warmed) compression test numbers from today…

1: 170
2: 165
3: 163
4: 163
5: 165
6: 175

Does this tell you anything that cyl 6 is much higher than all the others?

Compression looks fine.

 

[whitey45]

“ things bang together’