Cold start knock

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19jacobob93

19jacobob93

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Feb 12, 2014
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734
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Gold Coast, QL, Australia
As the mornings are getting colder I'm starting to notice what sounds like a bottom end knock in my engine.
It only happens some cool mornings, not all, but when I first start the engine I start to hear a knocking sound as the revs settle out below 1000.
Its more of a deeper noise than the lifter tick I sometimes get and sounds like its coming from the bottom end and can be heard in the cab with the windows up. It is effected by the revs.
It stops after 45 secs to a minute and once the engine is warm everything runs fine and quietly, no knocking or any ill effects, and no further knocking will be heard on starts later that day.
I'm running recommended 10w30 and the engine only has 210,000 KM on it and hundreds of these engines have gone well past 1 million KM with no internal work at all just oil/filter changes. It seems very early to be having what sounds like bottom end bearing wear, that somehow goes away when warm...

Any ideas or experience?

I have a video of the noise taken at around freezing point cause we are having an early cold snap around here at the moment. I am currently uploading and I will post the link when it finalizes
 
Is it parked level, or on a gradient? They can knock when they're on a bit on a angle, as the crank "slaps" the oil in the sump, particularly if the oil is a little overfull. Otherwise, I'd be suspecting the torque converter bolts have come loose, or even a stuffed engine mount - the drivers side one usually goes, and they can transmit some funny harmonics into the cabin. Could also be the harmonic balancer is on its way out, have a look to see if it's moved on the rubber damper. I'd be extremely surprised if it's a mechanical problem with the engine.

* It gets to zero degrees in Queensland? We haven't even had it that cold, so far!
 
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Originally Posted By: hpb
Is it parked level, or on a gradient? They can knock when they're on a bit on a angle, as the crank "slaps" the oil in the sump, particularly if the oil is a little overfull. Otherwise, I'd be suspecting the torque converter bolts have come loose, or even a stuffed engine mount - the drivers side one usually goes, and they can transmit some funny harmonics into the cabin. Could also be the harmonic balancer is on its way out, have a look to see if it's moved on the rubber damper. I'd be extremely surprised if it's a mechanical problem with the engine.

* It gets to zero degrees in Queensland? We haven't even had it that cold, so far!


It does it when parked on flat, but yes it is slightly overfilled but only by about 200ml tops, registers literally 2mm above the full mark so I doubt it's what you'd call overfilled.
It could be something in the transmission but I'm 99% certain it's coming from the engine.
The engine mounts are a little tired given their age and there are some vibrations at idle sometimes but I think this is a seperate and small issue
The harmonic balancer again is original and does look like it has a slight wobble on when I look at it with the engine idling. Not sure if this is an issue though.
I would be beyond surprised too if it was a bottom end knock in one of these too, but it sure sounds like it. Maybe there is oil restriction to one of the bearings? Again I'd be surprised because it started recently and these past two years I've done a lot of 2-8k OCIs including flushes and cleaning additives. Engine is spotless inside and the oil stays clean for a long time.

Yep! Not here on the coast, been down to about 8c here but I slept at Mt Kynoch the other night at Toowoomba which is about 850m above sea level 2 hours in land. Was 2c when I started the car at 8am so it would have been colder earlier in the morning!
 
200ml over won't cause a problem. To try and narrow it down, take a long screwdriver and use it like a stethoscope, holding it on various parts of the engine and putting your ear on the handle. Have a helper if possible to vary the revs for you. Pay some attention to the serpentine belt tensioner area too, they can also cause some funny noises when they're on the way out. If all else fails, turn the radio up a bit more!
 
Originally Posted By: hpb
200ml over won't cause a problem. To try and narrow it down, take a long screwdriver and use it like a stethoscope, holding it on various parts of the engine and putting your ear on the handle. Have a helper if possible to vary the revs for you. Pay some attention to the serpentine belt tensioner area too, they can also cause some funny noises when they're on the way out. If all else fails, turn the radio up a bit more!

Nah I always overfill it very slightly and it settles to around the full mark and stays there.
Yep I might have to do that! As for the tensioner pulley, it has come off before and I replaced it 2 years ago with one from a wreckers. Its squeaking again so I'm going to replace it again soon with a new one this time!
I think I'll just have to ignore it for now and see if it gets worse. I doubt it's anything serious on one of these engines though. I have a few viscosities of oil in my stash - 10w30, 15w40, 15w50 and 20w50 so I will see how they go with noise and performance over the next year or so!
 
Do you have a manual oil pressure gauge you can put on it to verify oil pressure?
I had a friend that had a late 90's Ranger that developed a knock. He hooked up an oil pressure gauge and it had very low pressure. So the engine came out and placed on an engine stand, and when he removed the oil pan he found the culprit. Ford didn't use an actual oil pan gasket they used silicon instead. And there was a lot of it used because the pick up screen for the oil pump was nearly plugged solid. This truck was bought brand new so it absolutely came from Ford that way. He took pictures of the pick up screen and contacted Ford about it. It took a lot of phone calls but they ended up reimbursing him for the cost of the rebuild.
 
Originally Posted By: jrmason
Do you have a manual oil pressure gauge you can put on it to verify oil pressure?
I had a friend that had a late 90's Ranger that developed a knock. He hooked up an oil pressure gauge and it had very low pressure. So the engine came out and placed on an engine stand, and when he removed the oil pan he found the culprit. Ford didn't use an actual oil pan gasket they used silicon instead. And there was a lot of it used because the pick up screen for the oil pump was nearly plugged solid. This truck was bought brand new so it absolutely came from Ford that way. He took pictures of the pick up screen and contacted Ford about it. It took a lot of phone calls but they ended up reimbursing him for the cost of the rebuild.

Wow what a horrendous cost cutting measure haha I think these use a gasket or at least I've never heard of this happening.
I know someone with the same car with the same engine, only his has 960,000km on the clock! That is the original engine that has never had any internal work, that's why I'm a little concerned about mine having a knock at 210,000
frown.gif
 
Originally Posted By: jrmason
Do you have a manual oil pressure gauge you can put on it to verify oil pressure?
I had a friend that had a late 90's Ranger that developed a knock. He hooked up an oil pressure gauge and it had very low pressure. So the engine came out and placed on an engine stand, and when he removed the oil pan he found the culprit. Ford didn't use an actual oil pan gasket they used silicon instead. And there was a lot of it used because the pick up screen for the oil pump was nearly plugged solid. This truck was bought brand new so it absolutely came from Ford that way. He took pictures of the pick up screen and contacted Ford about it. It took a lot of phone calls but they ended up reimbursing him for the cost of the rebuild.
 
I would say you have piston slap. You say it's getting colder so it's more pronounced now, and easier to hear. Don't worry, it's not dangerous.
 
Do you have any kind of low oil pressure warning?

Gauges are rather inaccurate so it would be a good idea to at least hook up a test gauge to verify your getting adequate pressure. Once a knock develops it rarely goes away, whatever your hearing COULD be pressure/ viscosity related that only shows up when everything is cold.
 
Originally Posted By: chrisri
I would say you have piston slap. You say it's getting colder so it's more pronounced now, and easier to hear. Don't worry, it's not dangerous.

The symptoms definitely follow those of piston slap. Only it sounds like it would only be one piston, and the temperatures aren't that cold, it has happened at 10c/50f some mornings which is still fairly mild. Never heard of piston slap in these engines or at all in Australia since 99% of the population lives in the warmer coastal areas
 
Originally Posted By: jrmason
Do you have any kind of low oil pressure warning?

Gauges are rather inaccurate so it would be a good idea to at least hook up a test gauge to verify your getting adequate pressure. Once a knock develops it rarely goes away, whatever your hearing COULD be pressure/ viscosity related that only shows up when everything is cold.

There is no gauge and my model is a series 2 which have a pressure switch so the gauges are useless anyway. The series 1 models had a pressure sender with a real gauge but I don't have that
frown.gif

The oil pressure light works but goes off straight away upon start up and has never come on running thin oils in traffic with the a/c on in mid summer 105+F temps.
 
Piston slap is one of the few things that is loudest on startup, and quiets down in a minute or more of warmup.

Other than that, some sort of cam chain tensioner is the only possibility I can think of. Main and rod bearing knocks do not improve, with warmup.
 
I had a 3000GT that did that exact same thing,only on cold morning startups and only with synthetic oil. With conventional oil it was silent,no startup knock at all. Mine was definitely piston slap,it was pretty obvious,and car had only 40k miles on it. It just didn't "like" synthetic oil. I tried going back and forth a few times switching between conventional and synthetic oil,and like clockwork the conventional oil made the noise go away.
 
Originally Posted By: 440Magnum
Piston slap can be mistaken for bearing knock, and is MUCH more dependent on temperature.


I have had folks in my sphere of influence mistake carbon knocking for bottom end noise as well. Easily cleaned up with just a shot of Kreen in the fuel in minutes. Seems to happen a lot in city driving.

Piston slap is annoying but usually not an issue for long term ownership. We recently sold a "slapper" GM 6.0 with half a million miles on it, it still works every day in another state!

Terrible, those GM vehicles!
 
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