: 93-94 wrist pin problems????



BIGGUN
07-26-04, 11:19 PM
Is it true that 93-94 N*'s had wrist pin problems?
A friend has a 94 with major knocking at idle or throttle when warm or cold and was told that it is probably a wrist pin due to the fact thaT THEY WERE WEAK IN THOSE YEARS. Does this sound right?

He's looking at swapping a 97 block with his heads and accessories. Will this be compatible?

Thanks,
Kevin

BlackHatch
07-27-04, 12:28 AM
Is it true that 93-94 N*'s had wrist pin problems?
A friend has a 94 with major knocking at idle or throttle when warm or cold and was told that it is probably a wrist pin due to the fact thaT THEY WERE WEAK IN THOSE YEARS. Does this sound right?

He's looking at swapping a 97 block with his heads and accessories. Will this be compatible?

Thanks,
Kevin

Not sure about the compatibility, however, if a wrist pin is knocking audibly...better get ready for a motor swap. Sounds like he is.

I have never heard of a weak wrist pin issue previously on the 93-94 N* engines. I have a 93 N* with 175K hard miles on her. Runs like a top still. GM's are fairly notorious for sending out some motors with piston slap noise. My 1996 Camaro had that until it got to about 120 on the temp gauge and then the motor tightens up.

growe3
07-28-04, 01:58 AM
I've never heard of any wrist pin problems with any of the Northstars. I have two 93 STS's (85k and 155k miles) and they have never exhibited any knocking of any kind.

You may have a carbon "rap". If the Northstars are not opened up on a regular basis they tend to build up carbon deposits that can cause the noise you described.

Usual cure is to be sure your oil is full (half way up the dip stick index), then go out and do a few WOT's. If you see clouds of dust in your rear view mirror it is likely the problem. Use the on ramps to do rapid acceleration, to keep the engine clear and when exiting, down shift the transmission to slow you down, this will help keep the rings working free.

If you still have the original plugs it is probably a good time to replace them. Use only the dual platinum style; AC, Champion, etc.

-George

growe3
07-28-04, 03:30 AM
He's looking at swapping a 97 block with his heads and accessories. Will this be compatible?

No. Although the block will probably bolt up, the sensors were different, and located in different places. If you decide to get another engine get a 93-94 for a sure fit. I'm not positive, but I think a 95 may swap in.

-George

blb
07-28-04, 07:23 PM
Yes, this is an issue with '93 and early '94 Northstars. There is a TSB on it. If I can locate my copy, I'll post the number and more information.

growe3
07-29-04, 12:49 AM
Yes, this is an issue with '93 and early '94 Northstars. There is a TSB on it. If I can locate my copy, I'll post the number and more information.

I would be interested in reading the TSB. I have never heard any other complaints along that line, so it must not be to common.

Aside from the head gasket failures these engines are very dependable power plants.

-George

dallas5957
07-30-04, 03:41 PM
Have you located the TSB for the wrist pin issue?

Logandiagnostic
07-30-04, 11:01 PM
There were maybe 2-3 bulletins about the wrist pins. I have found 1 version. There may be some others....

That being said....I would find it hard to expect a warranty repair 10-11 years after the fact. That would indicate that yours was not effected. Your talking about a 1995 bulletin.

Anyway, heres the bulletin...



METALLIC KNOCK SOUND FROM ENGINE #47-61-42 - (02/01/1995)
SUBJECT: METALLIC KNOCK SOUND FROM ENGINE (DIAGNOSE/INSTALL NEW PISTON WRIST PIN)

MODELS: 1993 CADILLAC ALLANTE 1993-94 CADILLAC ELDORADO AND SEVILLE WITH 4.6L NORTHSTAR ENGINE (VINS 9, Y - RPOS L37, LD8)

CONDITION:

SOME OWNERS MAY COMMENT ON AN ENGINE NOISE DESCRIBED AS A HYDRAULIC VALVE LIFTER TICK. THIS NOISE MAY BE HEARD AT ENGINE IDLE WITH ENGINE SPEED LESS THAN 1000 RPM.

CAUSE:

THIS NOISE MAY BE CAUSED BY A DAMAGED PISTON WRIST PIN OR EXCESSIVE CLEARANCES BETWEEN THE PISTON, PISTON WRIST PIN, AND CONNECTING ROD WHICH MAY RESULT IN ENGINE FAILURE. ALL 1993 AND SOME EARLY 1994 MODEL YEAR 4.6L NORTHSTAR ENGINES WERE EQUIPPED WITH PISTON WRIST PINS CONTAINING A FORMED STEP AT THE CENTER OF THE PIN. A NEW PISTON WRIST PIN WITH CONSTANT (STRAIGHT) WALL THICKNESS WAS INTRODUCED DURING THE 1994 MODEL YEAR REPLACING THE FORMED STEP DESIGN (FIGURE 1).

CORRECTION:

PERFORM THE FOLLOWING STEP **BEFORE** REMOVING THE ENGINE ASSEMBLY FROM THE VEHICLE:

USING A STETHESCOPE, IDLE THE ENGINE AND ISOLATE THE PISTON WHERE THE KNOCKING SOUND IS MOST EVIDENT.

**AFTER** REMOVING THE ENGINE, INTAKE MANIFOLD, CYLINDER HEADS AND LOWER CRANKCASE ASSEMBLY:

1. INSPECT THE SUSPECT PISTON AND WRIST PIN FOR DAMAGE. IF THE PISTON WRIST PIN IS DAMAGED, THE PISTON, RINGS, WRIST PIN, CONNECTING ROD, CONNECTING ROD BEARINGS AND BOLTS MUST BE REPLACED. 2. INSTALL THE NEW PISTON WRIST PIN WITH A CONSTANT (STRAIGHT) WALL THICKNESS. TO ENSURE PROPER ENGINE BALANCE IS MAINTAINED, REPLACE THE REMAINING FORMED STEP DESIGN WRIST PINS. 3. IF THE PISTON WRIST PIN IS NOT DAMAGED, INSPECT THE CONNECTING ROD TO PISTON WRIST PIN CLEARANCE (0.002 MM TO 0.022 MM) AND THE PISTON TO WRIST PIN CLEARANCE (0.002 MM TO 0.013 MM). IF THE CLEARANCE BETWEEN THESE COMPONENTS IS OUT OF SPECIFICATION (REFER TO SECTION 6A2 OF THE SERVICE INFORMATION MANUAL), REPLACE AS NECESSARY.

1993 MODEL YEAR 4.6L NORTHSTAR ENGINES ARE EQUIPPED WITH FORGED CONNECTING RODS. THE CONNECTING ROD BOLTS MAY BE REUSED IN 1993 ENGINES WITH FORGED RODS.

1994 MODEL YEAR 4.6L NORTHSTAR ENGINES ARE EQUIPPED WITH POWDERED METAL RODS WHICH USE ROD BOLTS DESIGNED TO YIELD WHEN TORQUED TO SPECIFICATION. THUS, THE BOLTS MUST BE REPLACED IN A 1994 4.6L ENGINE WHENEVER A ROD CAP IS REMOVED.

CONNECTING RODS MUST NOT BE INTERCHANGED BETWEEN 1993 AND 1994 MODEL YEAR ENGINES DUE TO CRANKSHAFTS USED SPECIFICALLY WITH EACH TYPE OF CONNECTING ROD. IF THE CONNECTING RODS ARE INTERCHANGED, THE ENGINE WILL BE OUT OF BALANCE.

IMPORTANT: NEVER REUSE CONNECTING ROD BEARINGS WITH RUN TIME. WHENEVER A ROD CAP IS REMOVED, ALWAYS REPLACE THE BEARINGS AND PERFORM A CLEARANCE CHECK WITH PLASTIC GAUGE. REFER TO SECTION 6A2 OF THE SERVICE INFORMATION MANUAL FOR THE PLASTIC GAUGE PROCEDURE.

WHENEVER SERVICING THE CONNECTING ROD AND/OR MAIN BEARINGS IN ANY 4.6L ENGINE, APPLY A COAT (COMPLETELY COVER) OF LUBRIZOL, P/N 9780631, (CANADA P/N 992869) TO THE BEARING SURFACES AND CRANKSHAFT JOURNALS.

WE BELIEVE THIS SOURCE AND THEIR PRODUCT TO BE RELIABLE. THERE MAY BE ADDITIONAL MANUFACTURERS OF SUCH PRODUCTS. GENERAL MOTORS DOES NOT ENDORSE, INDICATE ANY PREFERENCE FOR OR ASSUME ANY RESPONSIBILITY FOR THE PRODUCTS FROM THIS FIRM OR FOR ANY SUCH ITEMS WHICH MAY BE AVAILABLE FROM OTHER SOURCES.

IMPORTANT: WHENEVER THE 4.6L ENGINE HAS BEEN DISASSEMBLED AND REASSEMBLED, THE PRIMING PROCEDURE MUST BE PERFORMED. REFER TO SERVICE BULLETIN 476110 FOR ENGINE PRIMING PROCEDURES.

PART INFORMATION:

REFER TO THE FOLLOWING PART NUMBERS WHEN REPLACING THE PISTON WRIST PIN. DESCRIPTION PART NUMBER ----------- ----------- PISTON AND PIN WITH RETAINER 12552630 PISTON RING KIT 3543903 CONNECTING ROD AND BOLTS, 1993 MODEL YEAR 1647401 CONNECTING ROD AND BOLTS, 1994 MODEL YEAR 3533480 PISTON PIN AND RETAINING RING KIT 12554262 CONNECTING ROD BEARING KIT 3543901 CONNECTING ROD BOLT, 1994 MODEL YEAR 3533482

PARTS ARE EXPECTED TO BE AVAILABLE ON JANUARY 23, 1995.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE: LABOR OPERATION: J1300 - FOR RIGHT BANK J1301 - FOR LEFT BANK J1307 - FOR BOTH BANKS

USE PUBLISHED LABOR OPERATION TIME.



Logan Diagnostic
www.airbagcrash.com
www.crashdatainfo.com
www.logandiagnostic.com

growe3
07-31-04, 10:54 AM
An interesting read DTS. I have never heard of Northstars having any wrist pin problems. Both of my 93' STS's run and sound just fine with fairly high milage on them. I wonder if it really was wrist pin (ticking) noise, it might have been carbon rap from the cars being driven to mildly and GM hadn't figured it out yet.

-George