Cold-start knock

[Qwimby1]

It's a little hard to describe. Definitely a rap in the motor for the first few seconds after sitting overnight. It was random, not any pattern, and only lasted for a few seconds. It stopped once the RPMs dropped and would not occur again until the car sat overnight. It was definitely not a valve noise. Car is a 2014 with 60,000 miles.

I'm thinking maybe the check valve in the filter failed and oil drained back out overnight. It's a Massey filter. I normally change my own oil, and use OEM filters, but I happened to have it done by an excellent shop recently.

It didn't happen yesterday morning when I took it to my wrench and left it for him to hear it stone-cold this morning. He didn't hear anything on startup today.

I'll let it sit overnight tonight and see what I get tomorrow, but I plan to change oil and filter tomorrow anyway. I'm also going to get off my duff and get an oil pressure and temperature gauge installed forthwith.

[DarkPira7e]

You're overlooking the simple thing- did you check the oil level? What weight oil did they use? What brand? What weight do YOU usually use?

The oil filter is a very easy and cheap part to change, stick with what works best for you. If this was even more than a one-off thing

[cmiovino]

Almost all oil filters have anti-drain back valves now, even cheap ones. I'd still stick with OEM though. Can't beat them. Everything is correct and they're not expensive. The good news is changing this while there's oil in the car is easy, unlike if it sat under the car.

Oil weight and even brand can sometimes cause minor differences like this if you're really in tune with your car. No telling what they put in.

Just my opinion, but oil, the oil level, filters, etc are all very important and I tend to only do them myself. If I absolutely couldn't, I'd take it to a shop that would put the oil/filters I supplied on at least.

[Qwimby1]

There's plenty of oil in the car. I had several things done to it about 500 miles ago at an excellent shop, but an employee changed oil and filter which I didn't order. I made my feelings about that known. I also was not able to determine what brand oil, but it is 0w20. I plan to change it back to my customary Mobil 1 5W-30 and OEM filter soon, but I just hadn't gotten to it. It gets changed today,

[Qwimby1]

Left it overnight for my wrench to hear on Thursday morning but it did nothing. Didn't do it again yesterday morning. Yesterday I changed the oil and filter and it sat overnight, then made a Hell of a racket this morning. I think even louder. Almost sounds like somebody's pounding on the block with a hammer. It lasts just a few seconds until the RPMs drop. Then it won't do it again until it sits until stone cold overnight.

This is a seriously scary noise. I'll try to record it tomorrow morning. Cannot figure out what could be causing this.

[Qwimby1]

Nothing this morning after banging like Hell yesterday morning. The previous oil was Quartz 0-20 with a Massey filter. I changed it back to my customary Mobile 1 5-30 with an OEM filter and it knocked the first morning I started with that setup. Now nothing again. It's probably reasonable to rule out oil starvation at this point, so that could indicate something external…maybe an alternator or air-conditioning compressor bearing, but there's no pattern to it, just random knocks. It always stops just prior to the RPMs dropping, but I can't figure how that could be related. It's hard to pin down the location because I have to jump out of the car and run to get under the hood after after starting it. Think I'll rig up my phone recording under the hood every time I start it for now.

[Ultramaroon]

Journal bearings can wear to the point of being sloppy enough to knock before oil pressure kicks in. If this is the case, the engine can take it for a while, but it's days are numbered. Thick oil can stave off the inevitable for a time.



Don't take it anywhere you can't afford to have a catastrophic failure.

[tomm.brz]

stupid question ... we are not talking about normal sound of cold start of stock tune when car is left overnight in the cold , right? because almost -20 of forced ignition timing at more than 1500rpm are loud

[Qwimby1]

It has 60,000 miles on it, about 32,000 of which I've put on. Borla header, free-flow front pipe, Phantom electric supercharger, and OFT tune. I don't use the supercharger very much and I try to hold peak RPM to 6000.


It has done it intermittently with both the Massey and OEM oil filter so I don't think oil starvation is a factor. If it was a journal bearing I would think it would do it all the time. Am I right about that? That's the crazy part. It just doesn't do it all the time, and when it does start normally it's quiet as a mouse.

[Qwimby1]

Originally Posted by tomm.brz

stupid question ... we are not talking about normal sound of cold start of stock tune when car is left overnight in the cold , right? because almost -20 of forced ignition timing at more than 1500rpm are loud

Thanks. I'm not sure I fully understand your point, but I'm in Florida so we're talking 75 overnight this time of year. Starting idle is always about 1300, and then drops to 800. But the maddening part is why it doesn't do it consistently.

[Ultramaroon]

Originally Posted by Qwimby1

If it was a journal bearing I would think it would do it all the time. Am I right about that? That's the crazy part. It just doesn't do it all the time, and when it does start normally it's quiet as a mouse.

That has me scratching my head too. It takes a little over a second for the oil pump to fill all the galleries.


There's also a thing where the center lock for the intake VVT phasors start to jam open. Depending on how one of the intake cams comes to rest, it may also knock until it pumps up. I've only read about it. No firsthand experience but it makes sense to me.

[tomm.brz]

You really need to take a video of it happening

[Qwimby1]

Originally Posted by tomm.brz

You really need to take a video of it happening

I videod it the last two days but it hasn't done it. I'm going to video it every morning until I catch it.

[Qwimby1]

It's the front-pipe cat! A Werks free-flow cat pipe. The core was rattling around until it took a few seconds to get hot and expand. My wrench caught it this morning. I guess I'll just run it this way for a while because I can't see any harm. The worst that can happen is it'll gradually disintegrate and blow itself out the back. Then I'll just put in another one. FTspeed has a Motive Concepts free-flow cat pipe for $420.

I was convinced I was looking at serious, going into the motor, stuff to fix. I really appreciate everybody's input.