Not so good first drive of the year. UPDATE 9/12/14 VIDEO

[BARRACUDA1968]

Decided to take the GN out today so I changed the oil with a WIX filter and Mobile 1 10w 30.

I left on an 80 mile 1 way trip to my home town. All went well until I stopped when I got there to get fuel. Once I fueled up and left station the motor started to make noise, I would describe it like a diesel sound. At idle the motor sounds perfect. Under a load it made noise??

I went 4 miles easy to a bar and had lunch. After eating I left and the noise wasn't as bad. Thought Maybe I got bad gas so I added a can of seafoam. Drove across town and let my brother in law listen to it. He builds high end stock car motors and his opinion is a rod bearing.

My oil pressure has never been stellar in this car but I have read several threads which said a lot of guys have had the same pressure as me so I never bothered with it.

Not sure what happened but I drove the car home 80 miles and it ran fine but under a light load I hear a diesel sound. The only other time I have heard the same sound was after a pass at the strip on the return road. It didn't really concern me because it went away, I kind of figured it may be exhaust rattle etc.

If anyone has any ideas my ears are open. I will check TQ bolts in the morning but I'm doubting that at this point. We just put a new converter in last fall.

Too bad because this motor is supposed to have under 4000 miles and it running pretty good.

 

[hiboom]

I had a motor do the same thing from 1500-2500 rpm I would here this noise let off and it would go away idle nothing ended up rod cap loose


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[BARRACUDA1968]

I had a motor do the same thing from 1500-2500 rpm I would here this noise let off and it would go away idle nothing ended up rod cap loose


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That would sum it up right there! What can I do about it at this point if thats it?

 

[earlbrown]

When you say 'diesel sound' are you talking about part throttle detonation? Do you have a EGR chip and a disabled EGR?


If it was a rod bearing I'd like to think after 80 miles you would have moved from a 'funny noise' to a ride on a rollback. Plus rod bearings tend to make noise at idle and they never make less noise (with no other changes)

 

[BARRACUDA1968]

The sound was loudest at part throttle and would come and go almost like a lifter pumping up and bleeding down but it sure didn't have a lifter sound. I just got to the shop this morning and started the car and no noise what so ever at any rpm range. I'm letting it warm up right now. The funny thing is yesterday right after changing the oil before I left my oil pressure gauge read 45 psi cold at start up and it always read 60 before. I have suspected my oil pressure gauge which is a VDO in the AVC dash package to be inaccurate. My temp gauge doesn't' work right either. Anyway when I got about 30 miles up the road I noticed my oil pressure was reading 25 psi and dropped to 15 psi at idle. The gauge has never been consistent so I figured I would check the gauge and sending unit when I got back. Again it has acted up before and I have read several threads with other people having the same oil pressure issues no it never really bothered me.

I did go from a 10w40 to a 10w30 yesterday and added ZZP for the first time. Same filter as before. I'm wondering now if maybe I had a pressure problem somewhere if that is possible because this morning I have a lot more oil pressure at start up.

I'm not sure on the EGR question? How do I tell?

I'll let it warm up real good and post back.

 

[we4Mateo]

Watching closely. These cars are weird.

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[BARRACUDA1968]

I let it get up to temp so the oil was good and hot. Oil pressure dropped to 25 psi at idle and 18 in gear which it has done since I've owned it. No real noise like yesterday. If I get my head under the hood I can hear the sound, almost like a "clatter" sound when I hit the throttle. You can't hear it in the car you have to be under the hood. It sounds internal to me but I have read so may post about noises sounding like a rod bearing etc and not being the case so I'm not going to jump to any conclusion yet but I have my suspicions.

I will pull the belt and see if the noise goes away. Then check the balancer. I also will cut open my oil filter I took off yesterday. There was nothing on the drain plug. Then I'll check the TQ conv bolts. Maybe they came loose. I did feel a slight vibration yesterday when it was making the noise under load. My brother in law felt it too.

If I get lucky and find the noise I'm still concerned about oil pressure. Could be a faulty gauge or sending unit but if not that might explain a few things.

One other thing I forgot to mention, I was going up a slight incline at maybe 25 mph and when the clatter started I hit the alky test button and the sound went away. Any clue there?

 

[Pronto]

Seeing any knock on the Scanmaster?

 

[Lil Truck]

I had a simular noise but it was easy to detect the problem, slow building boost the waste gate puck was stuck open on 3" DP.

 

[BARRACUDA1968]

Never checked the SM, I didn't think it recorded anything unless WOT which I didn't try.

So far the TQ converter bolts are tight. I found a small leak on the flange on the bottom of the turbo but nothing major. I have a new leak on the driver side valve cover so I will replace that today and check rockers. It sounds like it's on the drivers side anyway. I have a small ticking noise on the drivers side that I could hear at the drive through yesterday, may be a lifter or exhaust leak not sure. I looked at the drivers side header and can't detect any obvious leak from suit or anything. I'm about ready to cut open the old filter now. If I don't find anything I'll cut open the new one.

I'll post as I go but if anyone has any ideas please post them and I will check back regularly today.

 

[earlbrown]

Has the drivers side header been welded recently. Sometimes HUGE cracks can manifest and just flat out can't bee seen while mounted on the car.

One 'test' you can do is to tape some toilet paper on a stick and use it as a probe. Poke around where the pipes meet. If the TP finds a leak, it'll start dancing.


Just for grins see if the exmanifold bolts have backed off any. Are you running manifold gaskets?

 

[Just a Six??]

I've had a pancaked rod bearing & a loose crank sensor that made the same kind of noise right about 2K RPM . Take off the belt & if you still hear it get the front end on jack stands & get a good close listen with a buddy bringing up RPM. My crank sensor was just a tiny bit loose & I guess the vibration made it move & hit the balancer teeth but only at that RPM. 3 people all thought the noise was up higher in the engine & sounded almost like a bad bearing in the turbo. If that all checks out good remove the fuel injector wires one a time & if it goes away it's a possible sign of the rod bearing or cap. This noise drove me crazy for a good few days each time it happened so just take your time & one step at a time.

 

[BARRACUDA1968]

My header on the driver side has been welded so I will try and see if I can find the leak if there is one. Hard to tell.

I cut open the oil filter with tin snips and it's clean, nothing in there.

I'm changing the oil now and going back to 10/40 weight. I may have a lifter issue at this point. I expected to find material in the filter if I had a bearing issue.

I will check some of the other suggestions as I go. Thank you

 

[BARRACUDA1968]

Well I'm done for the day. I pulled the belt and still have the noise. I put a long screwdriver over every piston area on the valve covers and the noise is on the front piston on the drivers side. Pulled the valve cover and the rockers arms are tight when they are both closed. I can spin the push rod with my finger so I'm betting it's a rod bearing. Not sure what else it can be at this point. Both rockers moved up and down turning the motor over but I didn't put a dial indicator on it. I think the motor needs to come out at this point.

 

[hiboom]

Pull the plug wires one at a time on the drivers side rev up see if noise goes away


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[BARRACUDA1968]

I will try that tomorrow when I put the valve cover back on. I'm pretty sure at this point that the motor is hurt. It's not valve train noise it's deeper.

I'm in the middle of rebuilding my 474 stroker motor in my 78 Trans Am so the GN may have to sit this year out.

I may start a thread on what to do to rebuild this motor. I went full hydraulic roller motor on my 474 so I may see what you guys recommend on the Buick?

Not a good start to the year.

 

[we4Mateo]

Sorry to hear that.

 

[TT/Ameasap]

I would pull the pan Brett.
At least check the bottoms of the rod bearings and that may show you what your dealing with.

 

[we4Mateo]

I would pull the pan Brett.
At least check the bottoms of the rod bearings and that may show you what your dealing with.

Agreed. Easy enough to look at.

 

[hiboom]

I had sort of the same thing happen car developed a noise similar to what you described it was after a rebuild about 100 miles.dropped pan and no. 5 rod cap was loose replace bearing re torque bearing cap checked the torque on the rest of bottom end.I thought at that point what do I have to lose motor has about 11,000 miles on it now !