Rebuilt engine makes a two-tone whining / whistling noise at idle

[nd4sped]

Well make sure you let them know of any present issues of course. What is the next vehicle then?

 

[ctag]

Well make sure you let them know of any present issues of course. What is the next vehicle then?

Of course. Next up is an old NA miata that's been rotting in the back yard.

I woke up this morning with a "Eureka!" that it was the valve lash adjustment. I adjusted the valves after hand-grinding them to seat during the rebuild, but I've heard you're supposed to repeat the adjustment after break-in. So I went out before work and sure enough, all of the valves were too tight. I adjusted them back to middle-stock (.20 intake, .25 exhaust).

Unfortunately that didn't fix it. The whining/whistling noise came back after driving around for a while. Tonight I'm going to go back and check the clearance again, but I don't have much hope that it went out of adjustment and brought the noise back like that.

 

[nd4sped]

You adjusted the valves after hand grinding? Do you mean you used valve lapping compound and then ground them against the seats to try and regain a sealed surface?

This is not what valve lapping compound is meant for. Its more of a marking compound to PROVE that the seats are sealing against the seat withing a specific area of the valve. The light grinding makes a mark on the valve to show where the seal is. You want the seat position mark in the middle of the middle of the middle "angle" (usually a 3 angle valve job is typical). If the seat mark is too far to one side of the other then you get the grinding stones out and start making runs on the valve seat to adjust the angle until you get he correct sealed position on the valve.
There is a special bench tool for grinding down the valves.

Not to say you cant do it by hand but you usually do not get uniform results this way.

 

[ctag]

OK, I'm learning something new here. This donor engine was cheap because the previous owner said one of the valves wasn't closing all the way after he rebuilt it and he didn't want to muck with it any more. So I lapped all of the valves, but really went to town one two of them where a little bit of light could peek around the edge. Now I see that's not the appropriate process.

 

[ctag]

Also I hit a deer last night. Car needs a new headlight assembly before giving it away.

 

[nd4sped]

Ya the lapping process is just for checking the sealing area. Glad you figured this out, doing the stuff on your own is a learning process but in the end its the most beneficial because you are the only one with your hands on it. So you can always go back in your steps to see if you missed something somewhere.

Early on in my experience I ended up leaving out an O-ring that goes under a cam cap. I could not figure out my low oil pressure issue. Only figured it out when we had the engine out and we jumped the starter with the engine on the rack and valve cover off. Oil was spewing from between the cam cap and the head. Replaced the $0.005 O-ring and VOILA oil pressure was back to normal.

 

[ctag]

Both deer and I were unhappy: https://video.berocs.com/w/xrPm3sEamp2XMKQEKJFXNz

Broke the driver side headlight assembly



Went to a scrap yard on my lunch break and got a new unit



Installed and polished up!



All in all, not too bad. Glad it wasn't worse, and I learned something about defensive driving.

I'm taking the car to Atlanta this weekend, and then probably handing it off to new owners next week sometime.

 

[nd4sped]

I had a similar noise and turns out I installed the timing belt washer/disc (whatever ths f**k its called) that sites directly between the crank gear and engine block.

Nox Vidmate VLC​

Ya I brought that up already and he disassembled to verifiy, not the problem.

 

[ctag]

@daryelcorran I appreciate the troubleshooting advice though!

But yeah, already checked the big washer between the timing gear and engine. I sure wish it had been that simple haha.

Car did great on the trip to ATL and back. My last hope was that giving it some good miles to break in would result in whatever-it-is ceasing to squeal, but I'm home and the noise is still there loud as ever.

 

[nd4sped]

Cam torque? Left field here, but cam bolt washer? Im thinking of s**t that could rattle or create a hum. Hell a really bad injector can make a racket too.

 

[ctag]

Cam torque? Left field here, but cam bolt washer? Im thinking of s**t that could rattle or create a hum. Hell a really bad injector can make a racket too.

I dig that idea.

The service manual calls for the valvetrain retainer blocks to be torqued down at 18ft/lb but my torque wrench only goes down to 20ft/lb, so they are a little bit overtorqued. That's the only discrepancy I can think of. And I re-did them a few days ago when I took the camshaft out to look at, nothing changed in the noise.

Car is probably leaving this weekend. Tomorrow morning I'm going to go adjust the valves to the maximum clearance in the spec, just to be sure it's not a valve making the rocker rub on the cam. I'll take another look at the camshaft gear bolt while I'm there too.

 

[nd4sped]

.006 & .007 as I recall. But double check for the D16 as it might be different.

 

[ctag]

Just wrapping this up here.
The car got handed off back in September. I'm super glad it's going to good use!

 

[nd4sped]

So whats happening to the 98 Mothership?

 

[ctag]

So whats happening to the 98 Mothership?

The Mothership is in rough shape right now. It's to the point of starting to overheat at red lights. One of the upshots of the green civic being out of the way is now I'm not distracted with it, so hopefully I can make moves on doing the Mothership's engine rebuild.

 

[nd4sped]

Check your fan operation if you are overheating while at idle. You can also try turning on the AC to force BOTH fans on when you are sitting.

 

[ctag]

Check your fan operation if you are overheating while at idle. You can also try turning on the AC to force BOTH fans on when you are sitting.

I appreciate it haha. Fan works, running the cabin heat helps. Thermostat was replaced not long ago. I'm thinking the water pump is past due.

I could probably go in and replace it, but if I can make things work I'd rather just go ahead with the whole rebuild.
Overall the engine is struggling, doesn't like to start and is down to just a few ponies left under the hood.

 

[nd4sped]

Looking forward to your rebuild brotha!

Oh and, just fill it with wires! XD

 

[ctag]

I had a similar noise and turns out I installed the timing belt washer/disc (whatever ths f**k its called) that sites directly between the crank gear and engine block. Its a ring that keeps the belt aligned on the crank gear.

Thank you for the heads up! I don't have the car anymore, so I can only hope it's something somewhat harmless like that.

 

[nd4sped]

If it was a vacuum issue, you would be able to Speed Test tell by spraying a mixture of soap water around areas that you would expect vacuum leaks. (All around the manifold or any vacuum lines)

Also include the injector seal and brake booster.