cause of rod knock

[gtsfirefighter]

Just curious about something. Why is it a rod knock is common after a BHG? Mine is currently leaking so I don't drive it. I have not noticed any coolant in the oil yet. When I start the car it reaks of burning coolant, smokes, and then steams but does not overheat. Bottom end still sounds good. Do yall think I'm ok for now as far as bottom end goes. I won't drive it till it's fixed.

 

[The Weather Man]

Most people get rod knock avter head gasket jobs because there not careful enough and dont take enough time to do the job well.

 

[Kai]

Rod Knock is primarily caused by oil starvation, or oil emulsification iirc. When the HG blows, theres no coolant, no coolant causes block to overheat, oil starts to burn, bingo - rod knock. Then again, i had a similar problem, not BHG (got there in time), but driving the 300 metres from the bottom of my road to the top when the coolant was all gone caused there to be a horrible clattery noise and i thought the bottom end was gone. Still, ed said the bottom end was all good, as it wasnt run for any protracted period of time, and i got it sorted quickly enough.

 

[JonoTurbo]

One reason many people get rod knock after a BHG is they have the type of BHG where coolant gets in the oil. Coolant makes for crummy lubricant and actually can make the oil acidic. This then eats away at the bearings and if you repair your BHG without new bearings then you can easily end up with rod knock.

 

[RacerXJ220]

All that dirt, rust, coolant, scrapped gasket, pieces of grime, and other junk make it down to your oil pan during the BHG repair. Like drowning your engine with degreaser and letting it seep past the rings, or into another orafice without taking the time to clean it all up before putting it back together.

Some people, bolt everything back together afterwards, putting the oil in, etc. Some flush the oil, some don't. They just try to crank it right up sometimes even without priming the oiling system after it was dry.

either way it all ends up to oil pressure, and if you have any other fluid besides oil going through your motor's oiling system.

I hate my 7M because of that feeling in the back of my mind, saying BHG or rod knock, take your pick. It's probably the main thing that destroys 7M. Truck engines used for racing.

I've switched over the the JZ series motors in both my Supras, and I can't wait.

 

[trydrew]

The last three post are the primary culprits, but one of the main ones is the water in coolant. Basically, poor HG repair.

 

[jdub]

Read this...pretty comprehensive (in addition to the above):
http://www.supramania.com/forums/showthread.php?t=20486

A search would have brought that one up