Engine Rattle At Cold Start

[gilber33]

I just finished putting my e30 back together. I pulled the engine to replace many of the seals and to do a thorough cleaning. Anyways, when I started it back up for the first time it had a rattle that I would say was consistent with an engine that hasn't been ran in 3 months and it went away after 2 or 3 mins.

Next day I started it up and it was there again and then went away. I had put in 20w50 GTX and thinking that maybe its getting a little cool here for that and it's a bit thick. I drained it and put in Liqui Moly 10w40 with the friction additive and it was still there.

Any thoughts? I adjusted the valves when I had the head cleaned to .01 per all the write ups I looked at.

Cold start:

https://youtu.be/FgvzKqSup8Y

After a few minutes it was gone and sounds like this:

https://youtu.be/EXEATQvV7Kg

[willworkfore30s]

How long does it stay there? My 1989 F150 with a straight six always rattles for a few seconds on cold starts. I've been told by the old timers that most of them do and it doesn't seem to cause too much of an issue.

Maybe your oil pump isn't 100% or some oil passages are clogged.

[gilber33]

Just for a couple mins and then goes away.

[Lugnuts]

Sounds valvetrain related? Maybe pull the valve cover and double-check rockers/eccentrics/bolts/retainers are all properly seated.

If it is valvetrain, run the engine cold with the cover off to identify what's causing it?

[slum dog]

Sounds valvetrain related? Maybe pull the valve cover and double-check rockers/eccentrics/bolts/retainers are all properly seated.

If it is valvetrain, run the engine cold with the cover off to identify what's causing it?

Yes do this worst-case oil will just splash all around that area, I had a failing oil pump doing this when cold starting once the oil warmed up it was finding its way up.
Oil pressure was to low cold

[dnguyen1963]

Check to make sure that the oil feed line to the valves is not restricted. Cold oil might be too thick so the valvetrain is not sufficiently lubricated.

[gilber33]

Sounds valvetrain related? Maybe pull the valve cover and double-check rockers/eccentrics/bolts/retainers are all properly seated.

If it is valvetrain, run the engine cold with the cover off to identify what's causing it?

I took the cover off and everything looks to be OK. I'll have to check clearances again.


I see spec is .01, but I have read people going a little bit lower?

Check to make sure that the oil feed line to the valves is not restricted. Cold oil might be too thick so the valvetrain is not sufficiently lubricated.

Are you referring to the line that goes up and over the valves?


Someone had suggested an exhaust leak and all of the exhaust nuts had 1/2 turn to be tightened. After I did that, the noise went away from being a "single" louder tapping to what it sounds like a general noisiness in the valve train for a minute. I think there was a small exhaust leak adding to the sound. It now sounds more integrated into the sound of the engine and after a minutes it levels out.

[Lugnuts]

So case closed? It was an exhaust leak?

[gilber33]

So case closed? It was an exhaust leak?

Not really. It's still there. I think a small exhaust leak was amplifying it, but there's still some rattle on a cold start that goes away after the engine warms up a bit.


I'm going to try adjust the valves again. But I am going to get that special spring tool to make sure there are not any errors. I'm also going to set them to .009 as I've read in some threads has helped with valvetrain noise.


I also want to get a mechanics stethoscope to see if I can directly pinpoint where it's coming from.

[gilber33]

Yes do this worst-case oil will just splash all around that area, I had a failing oil pump doing this when cold starting once the oil warmed up it was finding its way up.
Oil pressure was to low cold

If I do this, will it be noticeable that let's say the oil pressure is too low? Like, will I see minimal oil on top that will gradually increase?

[Lugnuts]

Pretty sure I have my valve gaps down at .008. Can't recall. Might be .009. It is very quiet though (disclaimer: rebuilt 885 head w/lots of new parts).

Good idea on the stethoscope. Removing the valve cover should help you narrow down the location of the noise, and hopefully confirm there's sufficient lubrication taking place. The thin pipe/bar that runs the length of the head is best described as a "dripper" at idle. Maybe you have a single bad rocker that's got too much radial play (or, something in that neighborhood).

How quickly does the oil pressure light go off after starting the car?

[gilber33]

Pretty sure I have my valve gaps down at .008. Can't recall. Might be .009. It is very quiet though (disclaimer: rebuilt 885 head w/lots of new parts).

Good idea on the stethoscope. Removing the valve cover should help you narrow down the location of the noise, and hopefully confirm there's sufficient lubrication taking place. The thin pipe/bar that runs the length of the head is best described as a "dripper" at idle. Maybe you have a single bad rocker that's got too much radial play (or, something in that neighborhood).

How quickly does the oil pressure light go off after starting the car?

I will try a stethoscope and adjusting the valves before running it with the cover off.

I did confirm the oil pressure light comes on with key in pos 2 with all the other dash lights, but it turns off instantly when I start the car. Doesn't stay on. I'm hoping that's a good sign and I'm just looking at a rocker that needs to be adjusted.

[Lugnuts]

The light going off means the oil pressure is acting against the pressure switch in the side of the block. Going off straight after start is optimal. The same oil channel also serves oil to the crank and up to the head.

[Jaxx_]

It's hard to tell from the video, but piston slap is usually this type of sound that goes away once everything comes up to uniform temperature. For these old motors, I don't worry about it too much--but I would be a little upset if I just put it back together.

Did you take the head off? How did the bores look?

[gilber33]

It's hard to tell from the video, but piston slap is usually this type of sound that goes away once everything comes up to uniform temperature. For these old motors, I don't worry about it too much--but I would be a little upset if I just put it back together.

Did you take the head off? How did the bores look?

I did have the head off. Had it resurfaced and did a new head gasket. The bores looked excellent. Cross hatching was amazing still.

I double checked timing and rotated it several times before ever starting it and the whole assembly rotated smoothly.