Motor knock - 4.6 32v 1997 cobra

[cugar67]

Looking for an answer - I have read a lot of threads and posts trying to figure out what the h_ll I have. Here is the scoop: 1997 4.6 32V dohc motor - fresh bttom end - new stage 3 clutch, beraring, etc.- 5w-30w full syntheic oil- new high volume oil pump - new rod and crank bearings - new rings- blah, blag, blah, anyway the motor was perfect for about 250 miles then one day coming off the highway I noticed a knock. The motor has not even been over 5000 rpm as I was still breaking it in. I have pulled the plug wires one at a time and the knock remains. It increases as the rpm's increase. I thought it to be a lifter (tensioner I guess they call them now) but am not sure. Exhaust is tight with no leaks. Oil pressure stays at 20psi (hot) at idle and climbs to 60 psi when driving. The oil pressure does not flucuate when running. I have tried the poor mans stethescope and it seems loudest on the drivers side on the valve cover bolts by #8. I also listened to the bottom end by the oil pan and there is no noise there hardly at all just a good wooshing sound.

Also - I only rebuilt the bottom end, the top end of the motor is as it came from the factory. (stock) I am not sure what its life was before me with the exeption of knowing it had a supercharger on it before I go it.

I have read that chain tensioners, timming chain slap, lifters, rockers all can give the same noise.

Can anyone shed some light for this Cobra owner???? Anyone have the same problem.

 

[trinity_gt]

If the noise is definitely at the top end then pull the associated valve cover off and start sniffing around. Perhaps you've just got a collapsed lash adjuster ("lifter"... the tensioners used on the timing chains are different pieces...)

BTW, when breaking in a fresh rebuild I personally wouldn't use synthetic. Depending on the ring materials and bore finish, synth may not allow the rings and bore to wear in correctly resulting in glazing, rings that never seat, increased leakdown and oil consumption.

 

[cugar67]

Thanks Trinity GT

Thanks for the input. I should have also stated that I used 20w-50w oil to start things off then changed that oil after 150 miles and added the synthetic oil.

Would a collapsed lash adjuster follow the engine RPM's? This knock definately follows the RPM's.

I guess it is time to pull the valve cover - How would you know it is collapsed??

 

[jeremy canter]

First off you should NEVER run 10-30 in a 4.6 > your suppost to run 5-20 >nothing thicker!!! it takes a lot to get oil to the top of our motors .
>
second I also have a top end (knock ) but I have read many posts about our 32v rattling in the top end all have said the same thing change your lash adjusters if it don't go away> just drive it >
>
third > if you pulled the motor to rebuild the bottom end > WHY not do the top too? it's easy to have a shop just dust off the valve seats and put new valve seals in while your doing the bottom . you have a strong bottom end and a weak> (high mileage ) top end motor I just did head work on my car I know its a pain in the azz to pull the heads / so i know what your going threw

 

[cugar67]

Thanks Jeremy

Thanks Jeremy, it looks like I will dive into the valve train. Whooo Hoooo...

If anyone has any other suggetions or experience with this type of problem please let me know.

Thanks again to everybody.

 

[trinity_gt]

Thanks for the input. I should have also stated that I used 20w-50w oil to start things off then changed that oil after 150 miles and added the synthetic oil.

Would a collapsed lash adjuster follow the engine RPM's? This knock definately follows the RPM's.

I should start by saying that a valve noise of this type is typically more of a "tap" than a "knock." It might sound something like this:

YouTube - 4runner valve tapping

Since each valve opens once every two engine rotations, it would definitely change in frequency as the engine RPM changes. One important diagnostic tidbit is that a valve tap would not change in intensity with variations in engine load as piston and rod knocks would typically do.

I'd also say that 20W50 is pretty heavy, if only for a short distance. I recently put some 5W40 in my supercharged 2V thinking it'd give the reciprocating assembly a bit of cushion when running boost on hot summer days. I can hear though that the valve train doesn't much care for this viscosity for a bit after a cold start. I'll be switching out to some 5W30 or possibly 5W20 soon. The lash adjusters on these engines are pretty sensitive to oil viscosity.

I guess it is time to pull the valve cover - How would you know it is collapsed??

At the risk of making a bit of an oil mess, you might consider starting and idling the engine with the valve cover off to see if you can locate a noisy valve.

You might also test the "looseness" of each rocker arm with the engine stopped by rotating the engine with the crank bolt until each valve is on the base circle and then wiggling the rocker. Any one that's abnormally loose compared to the others should be suspect.

Some other vids to compare your noise against:

A piston (wrist) pin knock:
YouTube - wrist pin knock

A rod bearing knock:
YouTube - 99 DODGE STRATUS Engine Spun Rod Bearing Knock

 

[cugar67]

Thanks Mike

I listened to the You Tube link (4 Runner) and that is pretty close to what I am hearing although not that loud. It is definately not like the Dodge video and not like the wrist pin video as that noise would go away when the plug wire was removed which mine does not. The noise stays.

The intensity does not change but as you said the frequency does as the engine is rev'd up.

Again these were great aids for me and thanks again for the help it is greatly much appreciated. I guess its off the get a book on 4.6 32v motors to see how hard this is going to be and what it takes.

Anybody with experince on replacing lash adjusters please let me know. I have friend that said there is a tool that is used to remove the lash ajusters without pulling the cams. Hope so!!!!

 

[jeremy canter]

If it is the Trick flow tool of Ford Motor Co. tool yes it would make the world a better place when you change the lash adjusters> It hooks the cam and press down on the valve making pulling the roller rocker easy !!! and then the lash adjuster just pull right out like the old 5.0 lifters do . if there a little stuck get some niddle nose plyers and llift them out . I want to do all 32 on my motor but it gets a little pricy for 32 of them > I think the trick Flow lask adjusters are like $8.00 each at Summitracing.com > heres the part no. TFS-21400008 > = $256

 

[cugar67]

Thanks Jeremy, I will look into Summit Racing for the tool and the lash adjusters. Since I am going to be there I might as well change them all and be done with it.

I would assume that you need to rotate the cams to get them at the right spot for removal???? Turning the cranck bolt should do this I hope.

I'll post what I find for everyone to use in the future and cross my fingers this is it.

Soon the snake will be loose again...

Thanks again

 

[jeremy canter]

yes you WILL have to rotate the motor to change the lash adjusters > pull your plugs out it will help with the cam location and easy rolling the motor over > JUST" DO THE TWO VALVES AT A TIME INTAKE FIRST > THEN EXHAUST so you don't lose track of where your at > yes it does happen when the wife or kids is bugging you> take YOUR time > also I don't know how youo pull the valve covers but it's easyer for me to pull the intake off just for the room. the tool is cheap too I think it's only $30.00

 

[cugar67]

The tool I found was an OTC 7928 Valve Spring Compressor - $119.00 + shipping. I will look to see if I can rent one before buying it.

This seems to be the tool for the job - for both 2v and 4v applications. Gotta love "Goolge".

Summit Racing has the lash adjusters for $8.95 each.

I had a mechanic quote replacing the lash adjusters and he quoted $1,000.00 to do the job.

Is there anything needed to support the valves when you compress the springs or do they stay intact?

Thanks for all the information and the reply's...

 

[jeremy canter]

119.00 plus shipping is CRAZY stupid >and $1000.00 is that guy on drugs???> yea it takes some time to change them > but wow you can do a rebuild for that kinda money // the tool can be bought threw summitracing.com > the part is a TrickFlow tool part no. TFS-90518 > 29.95 plus shipping . the springs will hold the valves in place you just need to unload the roller rocker to get it out of the way to pull the lash adjusters out

 

[cugar67]

I thought I would drop a note to update.

Waiting on the tool and new lash adjusters from Sumit Racing.

Once I get them I will start the process of replacing them and let everyone know.

Summit said 2-3 weeks for delivery as they were out of stock on this tool.

Stay tuned

 

[cugar67]

Follow up - I had a mechanic friend of mine listen to the engine and after he suggest pulling the oil filter, take it a part and see what it contained. He thoughtthe knock was a rod. I did this and found metal and beraring material inn the filter. Looks like he was right, rod bearding. I cacelled thje lash adjusters and he is pulling the negine to see what the crack and rod bearing look like. Thanks for all in the input trying to figure this out. Sucks that it is this situsation.

 

[jeremy canter]

that sucks dude >
I know the Lincoin mark 7 motors are the same as our n/a cobra motors short of ther cams being diffrent > if you need parts fast try to find one for parts > might be cheaper on you than going to the dealer> do a search for more info before you jump in to too many parts . I'f you were close to my (Orange County,NY) I'd help .

 

[trinity_gt]

Follow up - I had a mechanic friend of mine listen to the engine and after he suggest pulling the oil filter, take it a part and see what it contained. He thoughtthe knock was a rod. I did this and found metal and beraring material inn the filter. Looks like he was right, rod bearding. I cacelled thje lash adjusters and he is pulling the negine to see what the crack and rod bearing look like. Thanks for all in the input trying to figure this out. Sucks that it is this situsation.

I'd hold up the engine, pull the K-member out and pull the pan to inspect the big-ends before yanking it and tearing it all down.

You said earlier:

"I have tried the poor mans stethescope and it seems loudest on the drivers side on the valve cover bolts by #8. I also listened to the bottom end by the oil pan and there is no noise there hardly at all just a good wooshing sound. "

and

"The intensity does not change but as you said the frequency does as the engine is rev'd up. "

I'm quite certain a rod bearing would be audible from the bottom end. I'm also certain that a rod bearing noise would increase in intensity, not just frequency, when loaded with varying RPM.

Did you actually pull the valve cover to at least investigate the top-end?

 

[jeremy canter]

^^ +1 on what he said > my car is noisy as HE!! in the top end when it's cold but after it warms up you don't even notice it > / and when I had my motor apart I did notice some shinny metal flakes in my oil . >but after i flushed the oil out and did my motor work it was gone > plus I'm useing a Mobil 1 filter right now (till I hit 500 miles)then its back to using fram .