mechanic blew my motor! help

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deansmachine

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ok this is what happend, I have a 1998 gmc savana with a 5.7. The van has 99000 miles and was skipping so my thought was to bring it in for a tune up, plugs, wires,....etc. I used a local garage that i have used before and had no issues with, they also have a pretty good rep. The owner did the work on the van. He replaced the plugs, wires, rotor, cap, fuel filter, pcv valve, and added a fuel conditioner to the gas. When I got the van he told me that the timing was 15 degrees off and he adjusted it to a relearn computer on the motor. This was a little strainge to me because the truck ran fine before, just a skip at 70-80 mph. I just thought at that time that he knew what he was doing and got in the truck and drove away. About 60 miles down the highway was my exit, I got off highway and the van idol went up down up down up down..... drove for another 5 miles and it just shut off. tried to start and it would half turn over and stop. Kinda felt like a dead batt.. Had my fathers mechanic tow to his garage and asses the issue. He told me the mechanic that I had do the work should have not touched the timing because the van will automatically adjust the timing when a new cap and rotor is installed, in other words the guy screwed up the timing so bad it dropped the oil pressure and burnt a berring in the engine. IS THIS EVEN POSSABLE?? THIS SUCKS ALL I WANTED WAS A TUNE UP NOT A TUNE DOWN
 
deansmachine said:
ok this is what happend, I have a 1998 gmc savana with a 5.7. The van has 99000 miles and was skipping so my thought was to bring it in for a tune up, plugs, wires,....etc. I used a local garage that i have used before and had no issues with, they also have a pretty good rep. The owner did the work on the van. He replaced the plugs, wires, rotor, cap, fuel filter, pcv valve, and added a fuel conditioner to the gas. When I got the van he told me that the timing was 15 degrees off and he adjusted it to a relearn computer on the motor. This was a little strainge to me because the truck ran fine before, just a skip at 70-80 mph. I just thought at that time that he knew what he was doing and got in the truck and drove away. About 60 miles down the highway was my exit, I got off highway and the van idol went up down up down up down..... drove for another 5 miles and it just shut off. tried to start and it would half turn over and stop. Kinda felt like a dead batt.. Had my fathers mechanic tow to his garage and asses the issue. He told me the mechanic that I had do the work should have not touched the timing because the van will automatically adjust the timing when a new cap and rotor is installed, in other words the guy screwed up the timing so bad it dropped the oil pressure and burnt a berring in the engine. IS THIS EVEN POSSABLE?? THIS SUCKS ALL I WANTED WAS A TUNE UP NOT A TUNE DOWN
Click to expand...

Start with the simple and are you sure you lost oil pressure??? The ECM will cut the fuel pump when the oil drops less then 6 psi so you don't burn out the crank bearings.

If your mechanic did try to adjust the timing by rotating the distributor, there could be a good chance that that the crankshaft position sensor is command up to 50 extra degrees of spark advance during engine cranking only. This in turn exposes the engine to higher than normal cylinder pressures which may result in an no start condition or with these symptoms:

1. Backfire during crank/start
2. "Kickback" during crank/start
3. "No" start
4. "Slow" or "hard" start/crank
5. "Grinding" or unusual noises during crank/start
6. Cracked or broken engine block at the starter boss
7. Broken starter drive housing
8. Broken starter ring gear on flywheel

Or any combination of the above mentioned.

Here is a class on how the timing is done on the vortec and you will need a scan tool to set it.

Below is the text from GM Service manual for 1998 Chevrolet C Pickup 5.0L, 5.7L, and 7.4L

According to this you don't set the timing but the timing offset.
You need a "Scan Tool" that plugs into the truck and can read the data from the trucks computer.
Besides from that, it looks like a normal timing procedure.

Setting Timing
Camshaft Retard Offset Test
The ignition timing cannot be adjusted. The distributor may need adjusting to prevent crossfire. To insure proper alignment of the distributor, perform the following:

With the ignition OFF, install a scan tool to the DLC.
Start the engine and bring to normal operating temperature.

Important
Cam Retard Offset reading will not be accurate below 1000 RPM

Increase engine speed to 1000 RPM.
Monitor the Cam Retard Offset.
If the Cam Retard indicates a value of 0° ± 2°, the distributor is properly adjusted.
If the Cam Retard does not indicate 0° ± 2°, the distributor must be adjusted.
Adjusting Camshaft Retard Offset

With the engine OFF, slightly loosen the distributor hold down bolt.
Important: Cam Retard Offset reading will not be accurate below 1000 RPM

Start the engine and raise engine speed to 1000 RPM.
Using a scan tool monitor Cam Retard Offset.
Rotate the distributor as follows:
To compensate for a negative reading, rotate the distributor in the counterclockwise direction.
To compensate for a positive reading, rotate the distributor in the clockwise direction.
Repeat step 4 until 0° ±2° is obtained.
Turn the ignition OFF.
Tighten the distributor hold-down bolt to 3N•m(25 lb. ft.).
Start the engine, raise engine speed to 1000 RPM and recheck Camshaft Retard Offset.

Start with scanning your ECM for any codes and re-check your timing and go from there.

Hope this helps and keep us posted

Molson02536
 
Don't know

The shop that towed the van said that a bearing is spun and its knocking loud, the truck has 10 or so psi oil pressure when I got it back from the tune up, I just thought it was where its supposed to run due to the fact that the mechanic told me the timing was off 15 degrees. I'm not a mechanic I have no idea about vans. All I know is the van ran fine, I had a tune up, now it's knocking loud??? What caused this???
 
deansmachine said:
The shop that towed the van said that a bearing is spun and its knocking loud, the truck has 10 or so psi oil pressure when I got it back from the tune up, I just thought it was where its supposed to run due to the fact that the mechanic told me the timing was off 15 degrees. I'm not a mechanic I have no idea about vans. All I know is the van ran fine, I had a tune up, now it's knocking loud??? What caused this???
Click to expand...

Over revving an engine when cold or worn in stretches the rod bolts that lets the bearing start to spin, once it starts the engine is gone. So to answer your question. But as others guy also know, cold oil can do it ( oil doen't properly lubricate till is hot ) worn oil that has broken down and has lost its viscosity do it also.

Main causes of spun bearing, again are people that think they can spin a bottom end to the moon when engine is cold or worn out when trying to warm it up. Look into "tensile load" its the load that is against the rod and bolts when it tries to yank the piston back down, at high rpm it can get really extreme, and its not only the weight of the piston. Its changing the direction of travel of the piston effectively increases the weight, the vacuum the piston is pulling and any detonation it has experienced etc. This will also stretch a rod bolt and loose the "crush fit" of the rod cap on the bearing.

Every spun bearing i've seen at a shop traced back to oil film failure of one form or another. Whether it's the engine builders error (bearing clearance insufficient) or oiling system failure (pump died or low oil level in pan or solvent contamination of the oil) or systemic pressure loss (bearing clearances opened up due to wear) the failure is the same.

The engine loses the amount of film of oil between crank and bearing, and the two come into direct contact. The resulting heat welds the bearing shell to the crank, which then starts the bearing spinning inside its saddle.

The Rod Bearings are crush fit to keep them from spinning, thats what I am referring to, but if the bolts stretch the caps lift and you lose your crush fit and proper clearance which cause your oil pressure to drop. BTW you get your OIL PRESSURE FROM YOUR CRANK SHAFT:D

Metal to metal contact is what you'll find, that could be from multiple things. Egg shaping a rod end by stretching it will cause metal to metal contact also, when the cap gets loose and you start banging on the top and bottom of the bearing it can bring the sides inward and touch, then it spins then the engine is done.

An experienced engine builder/racer should know this and professional race shops and other old timers too. Why do you think old school gear heads go and change rod bolts ONLY, and the point of that is to prevent bolt stretch and bearing failure. We drop the oil pan on your tour busses every 300.000 miles and replace the main and rod bearing with new bolt to ensure more trouble free of abuse down the hyway.

Hope this helps, a bad timing can also make your engine knock bad enough to think its a spun bearing. If the distributor was not tighten down and had moved while your driving, your timing may be off worst past what the engines PCM can handle to time which a detonation will cause the pistons to knock like a diesel engine, but if you had low oil pressure before you let the mechanic. You should of check the oil level or asked him why its reading low. Regardless, there are lots of good used 5.7 vortec in salvage yards going for as low as $300.00 in some places or try your luck on E-bay.

Molson02536
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thanks for your help

Ya, all i know is that I dropped the van off for a tune up and the oil pressure was around 40 psi. When i picked the van up the guage read 10-15 psi. Could timing alone cause this??
 
deansmachine said:
Can timing affect oil pressure
Click to expand...

Timing doesn't affect oil pressure, but the distributor shaft is what turns the oil pump to send it to the top of the engine. But mentioned that the oil pressure is created by the crank shaft and bearings.

The oil pump transfers the oil in the pan through the oil filter and then to the top of the engine where the oil flows through the journals. If the oil pump fails, then the oil will not make it to the top of the engine and you starve the engine of oil cause its all sitting in the oil pan.

Note that the oil pressure sensor is no to far from the distributor also. There is a good chance that the sensor lead wires could have gotten damaged when your mechanic turned the distributor and gave you a low oil pressure reading.

Low oil pressure would have been noticed by the ticking sounds of the lifters and a check engine light on the dash from a low oil pressure reading.

The only way you'll know for sure is to tear down the engine and inspect all your main and rod bearings to see if they all show the same sighs of oil starvation.

Good luck and keep us posted on your engine, btw the shop should have insurance for incidence like this so you can get your engine repaired.

Molson02536
 
I think the oil pump was not working correctly due to the fact the distributor was incorrectly adjusted. Dose this make sense to you? The sounds that you decribed above are exactly what happend, then the lights, then the engine shut off.
 
I feel bad for the shop, this is the last thing i wanted to tell him. I would even split the cost if he handles this like a professional.
 
deansmachine said:
I think the oil pump was not working correctly due to the fact the distributor was incorrectly adjusted. Dose this make sense to you? The sounds that you decribed above are exactly what happend, then the lights, then the engine shut off.
Click to expand...

Its been known to happen, and also common for oil pumps to fail also. But please keep all of us informed here at the forum on what's your next step on getting your van running again

Molson02536
 
is there a senser in the motor that will advance or retard timing if it senses a knock?
 
if so i think the mechanic should have caught this when he said the timing was off
 
deansmachine said:
is there a senser in the motor that will advance or retard timing if it senses a knock?
Click to expand...

The timing is adjusted by the ecm with the help of the knock sensor. Long story short, the distributor should of been positioned so that the rotor is pointed to the #8 stamped on the distributor when the engine is at TDC #1 piston and the advance is set to the highest the parameters of the ecm program.

The knock sensor picks up detonation and will start to regard the timing, there is how ever a timing wire that needs to be discontented if your going to use a timing light on the harmonic ballencer and with the use of a light gun should show 0'

If the timing wire was not discontented, the timing reading on the harmonic ballanecer will show the timing the ecm has justed it for to eliminate any detonation plus or minus. In most case if the engine is still cold and not at its operating temperature, it will show an advance reading.

This is why best to check the timing on a tech 2 scanner to time a vortec engine. Moveing the distributor and if it got lifted would miss align the distributor shaft from the oil pump shaft which could cause a oil pump failure.

End of class for now and keep us posted here on the forum.

Molson02536
 
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The mechanic that did the work is looking at the truck now, I cant wait to hear, oooo nooo sir that has nothing to do with what we did.
 
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