Rod Knock. With video.

[ask92]

Just installed the 7m. I had 2 7mgtes,one with rod knock and one with a bad headgasket. Out of that I made one thinking they would both hold. The knock only occurs after the car warms up a little(after about 30 seconds of running) and at over 2000 rpms.Any ideas? The oil pressure reads 20 psi at idle.Tomorrow i will be doing a compression test and listening around to see if I can pinpoint the sound.

[video=youtube;kFOmjEu7YZc]http://www.youtube.com/watch?v=kFOmjEu7YZc[/video]
Stop watching after 1 minute as its just me sitting in the seat cursing god.



EDIT:6/25/11 It was rod knock, only 1 rod.(see post #23, page 3)

 

[black89t]

right after the 45sec mark it sadly sounds like rod knock. with the # of 7m's ive knocked i can hear a rk from a mile away lol! its all about when it knocks. no load and floating the revs at around 2k. just get yourself a 2jzge and go na-t. i love 7ms but they're a constant battle...


sounds like you've got an exhaust leak too.

 

[hvyman]

I can't see the video on my phone but if it bhg and water got to the bearings they are toast.

 

[ask92]

This car is being rebuilt and put up for sale.And yes black89t good call there is a massive leak on the turbo, but that is not my concern right now if i have to repull the engine. Then my other supra will be getting a 1jz with the money .

 

[wardog]

You can replace the rod bearings with out taking the engine out. I have done that with my red supra and it is holding really good. Please stay away from KING bearings they are garbage , even the ACL bearings work better than KING.

 

[hvyman]

Acl aren't too bad. Just not made for high hp.

Replacing bearings for rod knock should be done correctly. Not the hill Billy way by just putting in a new bearing. Need to polish and possibly cut the crank for the right sized bearing.

 

[ask92]

Yea well as i said im just looking to get this car sold, so no need to build for high hp, just stock. And yes the new owner will be given all the details of the car. I dont see any way to change the bearings with the engine still in the bay. Unless you pull the subframe i guess, but it seems like itd be easier to just pull the engine IMO. Yea it looks like ill just get ACL bearings. Is there any way to test the main bearings to see if they need to be changed?

 

[hvyman]

Plastigauge.

Ya have to support the engine and drop the subframe. And its not even close to being the correct way of doing things. If its was a only car and absolute necessary to get by and the knock wasnt bad then id suggest it, but for the long run no way.

 

[ask92]

Well my knock doesnt seem bad at all, and when the crank was out it looked good. I will plastigauge it when i pull the engine i guess, would i notice anything that would tell me that the main bearings are bad when the engine is running?

 

[hvyman]

Just knocking.

What were the bearing clearances when you built it?

 

[bioskyline]

I dont see any way to change the bearings with the engine still in the bay. Unless you pull the subframe i guess, but it seems like itd be easier to just pull the engine IMO.

it is ghetto but you dont have to drop the subframe. if you undue the motor mounts and lift up the motor till it jams in the tunnel, you can wiggle the pan around and remove them. ive done it once but its a half ass fix, took longer than an re and re on the motor, and you cant clean the pan gasket surface enough to avoid a oil leak afterwards. pulling the motor is the easiest way to avoid problems later on.

also when you had apart before, did you put the bearings back on the journals the came off of?

 

[ask92]

I didn't check clearances as the engine didn't have rod knock before, and it didn't on this engine until it warmed up and got to temperature. The bearings were moved from one crank to another so it's possible the crank had been machined. I may just sell this car for 1500 with the rod knock.


Edit: The compression test went well, all the cylinders were within 7psi of each other after 2 passes, lowest being 120, highest being 127. It is low probably due to the fact that my compression tester is old and most likely doesn't read in the accurate range anymore.

 

[suprarich]

You moved bearings from one crank to another????

 

[ask92]

No, they stayed on the same crank..But apparently they weren't within spec(even though they looked good). O well i shoulda just done it right the first time, lesson learned. Should I machine the crank while its out of just get a new set of bearings? The crank didnt have any marks on it when i installed it, and i doubt this slight knock will cause any more. Should i also just go ahead and replace the main bearings as well?What about the bearings on the end of the crank that hold in the oil, they arent leaking but should I do them anyway?

 

[D.J.T.]

seriously? if you were going to open up an engine & take out the crank why not just get new main bearings? if they were original they been there for 20 + years. & idc if they look good, i still replaced all on my 5M.

 

[suprarich]

I would re-do the entire bottom end. When you get a rod knock, you are sending metal particles into the oil that end up being embeded into all bearings. Re-polish/grind the crank, all new bearings, new seals, wash out the oil pan, wash out the oil pump or replace. I would do that at a minimum. If it was my motor, a full rebuild with tank washing of the head and block would be done.

 

[ask92]

This car is being sold, im not really trying to go all out with it. The knock is so slight i cant imagine much of the bearing is gone, but i will clean and check everything. How can i figure out if the crank needs machining or not? Should i just machine it anyway regardless of how good it looks?

 

[CyFi6]

In my opinion, you should sell it as is. There is no point selling someone a half assed built engine, at least if you sell it as is they can repair it as they please. Everything needs to be measured, you can't tell just by looking at it.

 

[hvyman]

Need to take it to a machinest or a qualified person with the correct tools. Better to just find a quality machinest tho.

 

[Flateric]

I vote for the leave it as is if your selling it anyways. I seriously doubt you will increase the value of the car by equal or greater than the cost of repairing it properly. And as someone else stated, then they know what they are getting and can handle it the way they wish too. You are just burning up your time and money for no return, no car since it'll be sold, no added value and loss of many hours/days of your time.