Engine Knock...Please Help

[Zdreamin72]

I have a 2001 GMC Sonoma SLS Extended Cab with optional 4-Wheel drive.

My truck was overheated a couple times by my brother and subsequently blew a head gasket and recently found that it cracked a head. After sitting for approximately a year i was able to afford to have it sent in.

1700 dollars later there is an engine knock. I thought that it could be a rod knock but i have no idea how that could happen since it never ran low on oil and was never abused, besides the overheating a couple times.

The reason I am posting this is because i believe it to be for some other reason then a rod knock. The noise only happens while idling and stay the same level until 1400 RPM and then it gets about three times as loud until 1500 RPM. after that the noise goes silent as I increase the pedal the same rate.

If i snap the throttle after that the noise hits for a split second then disappears.

Additionally when the engine reaches 2300 RPM the Speedo begins to accelerate, this is all happening in Park mind you.

Anything would help. Thanks in advance.

[MT-2500]

Sounds like bad news.

What all did the 1700$ included done besides the knock?

Can you short the knock out by unpluging plug wires one at a time?
Was it knocking before repair?
What engine?
How many miles on it?
What is the oil pressure doing?
Was oil and filter changed with repair?

[b1lk1]

If coolant got into the oil there is a good chance that it took out the crankshaft bearings.

[4x4 blazerguy]

I have read on another forum that the 2000 & newer 4.3L V-6s used a timing chain tensionor. I read that they will knock up to 1500 RPMs There is suppose to be a TBA on this.
So you might look down this road. I have a knock in a 97 4.3L that knocks at about 1500 RPMs under no load & above 3000 RPMs under load. Yet it has been doing this for over 35,000 miles now. Oil pressure is 20PSI @ idle & 40-45 @ running speeds.
This is all the info I have, hope this helps.

[blazes9395]

All the 4.3's came with a standard timing chain, cam/sprocket setup, there was no timing chain tensioner used. Only the 'W' engines where upgraded with the balancer shaft to reduce engine vibration.

In this case, I would tend to agree with MT, this is not a good sign. Overheating an engine causes all kinds of problems such as block distortion, metal fatigue, bearing fatigue, piston damage, etc, etc. To crack a head means it was real hot and this heat probably caused bottem end problems too. Also, if the mechanic wasn't to clean doing the work, dirt and debris could have gotten inside the engine and starved one or more of the bearings.

1700 for a head job on a 01...whats the milage on the engine?

[MagicRat]

Originally Posted by blazes9395

In this case, I would tend to agree with MT, this is not a good sign. Overheating an engine causes all kinds of problems such as block distortion, metal fatigue, bearing fatigue, piston damage, etc, etc. To crack a head means it was real hot and this heat probably caused bottem end problems too. Also, if the mechanic wasn't to clean doing the work, dirt and debris could have gotten inside the engine and starved one or more of the bearings.

I agree with the above posts. You may have a collapsed piston. FWIW it does sound like additional overheating damage.

[rhandwor]

You can buy a quality rebuilt short block. They normally come with gaskets,new oil pump and timing chain.

[wafrederick]

Short block is not the way to go.Longblock is the way to go.I have done one shortblock to a Lincoln which the customer supplied,is not worth it transfering the oilpan,intake and exhaust manifold,installling the oil pump.The longblock is the way to go,all you have to transfer for parts are,the harmonic balancer,intake manifold and exhaust manifolds,valve covers and the sensor.Also put in new plugs and stick with the AC Delcos it came with.Any auto parts store reman engines are 100% to avoid,the warranty sucks taking it to one of their places and use the cheapest parts.Jasper is the way to go,cheaper than GM with a 3 year 100,000 mile warranty taking it to any Jasper dealer for warranty work.Also a general rule with any reman or rebuilt engine is to change the oil every 500 miles at first and do not use synthetic oil to break the new engine in,too slippery