Crankshaft pulley on 85 SR5 separated

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tercle
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My tercel:: 1985 SR5
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Crankshaft pulley on 85 SR5 separated

Post by tercle » Wed Dec 06, 2017 12:05 pm

Is the crankshaft pulley the same for all 3A and 4A engines?

The one on my 85 has come apart. The inside pulley intermittently slows down and stops while engine is turning.
Don't have time to pull the radiator until the weekend.
Trying to remember if it's all one piece or if there's a key or pin connecting the two pulleys.

tercle
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My tercel:: 1985 SR5
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Re: Crankshaft pulley on 85 SR5 separated

Post by tercle » Wed Dec 06, 2017 12:25 pm

I wonder if the rear pulley can be tack-welded to the rest of the assembly.

I just realized that the timing mark is on that loose pulley, so I definitely need to get a new one.
Is that rear pulley bonded to the rest with a rubber layer, making it a harmonic balancer?

What engines and cars have the same harmonic balancer?
I don't see a Tercel at PnP right now...

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Petros
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Re: Crankshaft pulley on 85 SR5 separated

Post by Petros » Wed Dec 06, 2017 4:05 pm

yes, it is a harmonic balancer. the other pulley bolts to the hub, so it would keep turning.

If the rubber bond failed you need to replace the assembly. there used to be shops around that could restore/rebond harmonic blancers, but buying another one is cheaper. That would only be if you can not find a replacement.

it is an essential piece of equipment, so do not be tempted to weld it together. The crank shaft will fail without a working harmonic blanacer in place.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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Petros
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Re: Crankshaft pulley on 85 SR5 separated

Post by Petros » Wed Dec 06, 2017 4:16 pm

the 4ac may use the same harmonic blancer, the crank, rods, pistons are all the same. except pistons are slightly larger dia.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

tercle
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Posts: 177
Joined: Sat Aug 27, 2011 9:57 am
My tercel:: 1985 SR5
Location: Seattle

Re: Crankshaft pulley on 85 SR5 separated

Post by tercle » Wed Dec 06, 2017 5:40 pm

Petros wrote:
Wed Dec 06, 2017 4:05 pm
yes, it is a harmonic balancer. the other pulley bolts to the hub, so it would keep turning.

If the rubber bond failed you need to replace the assembly. there used to be shops around that could restore/rebond harmonic blancers, but buying another one is cheaper. That would only be if you can not find a replacement.

it is an essential piece of equipment, so do not be tempted to weld it together. The crank shaft will fail without a working harmonic blanacer in place.
What if I welded it and only drove 100-200 miles and replaced it this weekend?
Is it possible it could damage the crankshaft that quickly?
What sort of damage to the crankshaft do you mean (I wonder if it's already been damaged)?

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Petros
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Re: Crankshaft pulley on 85 SR5 separated

Post by Petros » Wed Dec 06, 2017 10:09 pm

I do not know it will be harmed in 200 miles, but I would not do it.

the crank acts like a wind up spring, that goes though torsional cycles with each input from each piston firing. At cruising speed it goes though about 90,000 cyclic torsional inputs per hour. at 200 miles that would be close to 400,000 cycles.

The harmonic balancer limits the peak stress reaction of the crank, which is essentially whipping back and forth without the harmonic blancers to dampen this action. without the balancer the peak harmonic tortional stress reaction exceeds the fatigue strength of the crank, the balancer greatly reduces this peak stress so it is below the fatigue limit stress. think of it this way, cyclic peak stress may go up to 10,000 psi, in a brief spike, twice each revolution of the engine. With the harmonic balancer, it averages this out, it cuts off the peaks, and limits max peak stress to something like 5,000 psi (but spread out over a longer moment of rotation of the crank). So the crank does not have to be a massively heavy monstrosity. short periods of time, below the max allowable stress but above the fatigue limit, will not harm it. but the longer the repeated cycles above the fatigue limit, the closer you are to failure.

What you might try is to clean the surface of the lost bond good and than use contact cement or polyeurethane glue, as a temp fix. it may not last too long, but perhaps long enough to get you to the weekend. The risk is, if it the temp fix does not work, it puts a lot of stress in the crank.

the manufacturer would not install it if it was not necessary. I have seen failed cranks on engines that were run without a harmonic balancer. It may take a while, but eventually it will fail.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

tercle
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Posts: 177
Joined: Sat Aug 27, 2011 9:57 am
My tercel:: 1985 SR5
Location: Seattle

Re: Crankshaft pulley on 85 SR5 separated

Post by tercle » Thu Dec 07, 2017 12:04 am

Thanks for the information, Petros. I am renting a car for a few days.

tercle
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My tercel:: 1985 SR5
Location: Seattle

Re: Crankshaft pulley on 85 SR5 separated

Post by tercle » Fri Dec 08, 2017 10:58 am

Petros wrote:
Wed Dec 06, 2017 4:16 pm
the 4ac may use the same harmonic blancer, the crank, rods, pistons are all the same. except pistons are slightly larger dia.
I looked at a 86 Corolla, and the harmonic balancer is different.
It uses a single belt for alt, water pump and power steering.

tercle
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My tercel:: 1985 SR5
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Slipping harmonic balancer

Post by tercle » Mon Dec 11, 2017 9:41 am

Installed new harmonic balancer and all is good.

I had intermittent overheating and poor charging for weeks, and I think that the bonded pulley came loose hundreds of miles ago.
Since it is captive between the middle pulley and lower timing belt cover, the pulley and belt looked OK.
At idle, the pulley usually spun with the rest of the HB. (last week was the first time I saw it not spinning)

So my engine has absorbed a lot of hammering because of the split harmonic balancer for some time.

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Petros
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Re: Crankshaft pulley on 85 SR5 separated

Post by Petros » Mon Dec 11, 2017 2:15 pm

I have found that any overheating, even when not all the way into the red on the gauge, can compromise the head gasket. Regularly check your coolent level every few days (when cold), if you are loosing coolant that can not be explained by any leak, you should start planning on replacing the head gasket.

OTOH, if it is a minor coolant loss (like a cup or two a week), I have found that the head gasket sealer "stop leak" usually affects a permanent repair. this is not the normal stop leak, it is more costly (tyipcally $12-20), and it requires you to flush all of the coolant out of your system, install it with just water and run it for 20-40 min at idle (no drving it), and than you drain the system and let it cure overnight. It is than flushed out and you fill with coolant again. This kind has tiny Aramid fibers and some kind of plastic resin that requires it to cure. This has worked everytime I have tried it, and it is a lot cheaper and faster than a head gasket replacement. Note, this will not work if the head gasket is badly blown out, only if it has a minor leak.

Good luck. keep and eye on the temp gauge and check your coolant level regularly.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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