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Best and Brightest, chew on this one:
My 1990 745t (220k) cold-starts with an extra crank or two than usual. And when the idle settles, the voltage reading is down at (my best estimate) a little over twelve. If I rev the engine a bit, or simply start driving, I'll get this GRAWK noise, and the voltage jumps. If moving, the car hitchs a bit, as if someone yanked the e-brake hard. A month ago this would happen once, then all is fine. Now it takes a few revs, a few GRAWKS, and the voltage never seems to climp up into the happy-go-lucky 14 range.
more information:
-I replaced the alternator in February with a non-bosch (but of course, lifetime-guaranteed) Advanced Auto part.
-At first I thought the noise was in the back, perhaps the differential, plus or minus. Now it seems to be in the front, and I might have also heard a belt whine or slip during the last one.
I've observed this developing problem with bemused detachment, but I'm in the middle of a springy run of fixing the hell out of things (just did shocks/struts, headliner is next) and I think this is climbing its way onto the short list. Maybe even above "rattling door panels" and "install boost controller." If you have any thoughts or prior experience, I'm all ears.
-Nick
PS did make it through a complete swap to Bilstein HDs, front and back, with the help of the FAQ and previous comments on the board. I used many tips and avoided many others' prior mistakes. So far (50 miles in) the car tracks great, takes a set through the curves, and wallows so much less that I temporarily don't care about upgrading the sway bar, too...and no unexpected knocking and rattling from the front end. The HDs are the real deal. Certainly stiff, but in all the good ways. Thanks, BrickBoard.
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posted by
someone claiming to be spazman
on
Wed May 6 07:13 CST 2009 [ RELATED]
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Crank pulley?
Ari
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This is NOT an "ALL" "ALL" post.
Please put model and year in - not that hard.
Have you tried tightening your alternator belt?
--
George Downs, Bartlesville, Heart of the USA!
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You're obviously right about the categorization--when I copied it over to a post written from my account, I forgot to update the header. Point of order: should I repost it, or just let it lie?
The belt seems tight: "firm thumb pressure" in the middle of it causes a half-inch of deflection. I'll know more next time I start the car--rather, have someone else start it, so my head can be under the hood. I will pay close attention to the crank pulley--is there a clutch of some kind in it? Maybe that'll get the steering pump working hard again, too...
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The Crank pulley aka "Harmonic Balancer" is made up of two parts, bonded together in a thin rubber section.
The inner part (hub) is keyed to a small "nib" on the front of the crank sprocket, which is keyed to the crankshaft. The outer part with the belt grooves and timing notches is laminated or bonded to the hub. This lamination can loosen with age, allowing the outer part to slip or even stall momentarily under the belts, leading to two things:
1) The timing notches are no longer an accurate reference to crankshaft position.
2) The slippage can sound like belts squealing, and may even get bad enough to let the outer part come completely loose, causing things like radiator damage.
If your motor runs OK, but the pulley notch to belt cover marks don't agree with the Cam sprocket 0° setting, then the crank pulley outer part has probably slipped. Draw a white chalk line on the face of the pulley and check it frequently. Further slippage will make a jog in the chalk line.
Crank Pulley
Crank Sprocket
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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What you should watch is the alternator pulley.
I had a problem with my 164 a number of years ago sort of like this.
I had some doubts about my alternator but it seemed to test OK.
I was driving about 4 miles to work and put a battery charger on the car every night,
meanwhile trying to figure out what the problem was.
It turned out that the belt and the pulley were both shiny and although it didn't make any noise,
it would slip enough under load to keep it from charging.
I tightened the belt good and tight (after several weeks messing around) and the problem disappeared.
Here, you have the advantage of HEARING it slip!
--
George Downs, Bartlesville, Heart of the USA!
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Hi George,
It turned out that the belt and the pulley were both shiny and although it didn't make any noise, it would slip enough under load to keep it from charging.
How true! When this happened to me, I went to extreme methods to prove it, first installing a temporary ammeter, to confirm what the voltmeter implied. Then I rigged a speaker under the dash to listen to the unrectified AC available at terminal W on Bosch alternators. I learned the glazed belt and shiny pulley combined in silence.
On the 240 and 740, the alternator is set in rubber, so the effectiveness of tightening the belt depends on bushing hardness. On the 240, the belts span three pulleys, so the benefit of having dual belts to offset the smaller pulley contact is compromised as the bushings are compressed, leaving the inner belt loose.
After replacing belts and bushings, roughening the pulley grooves and verifying the end of the problem, I removed the speaker and ammeter. Mama mouse later found the grommet where my temporary ammeter wires had passed through the firewall.
--
Art Benstein near Baltimore
My dog is worried about the economy because Alpo is up to $3.00 a can.
That's almost $21.00 in dog money.
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Neat pic! Is the mouse alive? Looks VERY small!
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George Downs, Bartlesville, Heart of the USA!
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His brothers all outran him out the door; never did catch site of mama. I think they were just opening their eyes. Might be still alive. How long do field mice live? The photo is 5 years old. I plugged the grommet so they had to find a new home.
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Art Benstein near Baltimore
Never interrupt your opponent while he is making a mistake (Napoleon Bonaparte)
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