Uh oh... Help?

KNYFE · 05-19-2006, 06:06 PM

Well, I had my Supra at my car guys shop and he was going to put my new wheels on. We went for a short drive before so he could hear a new noise that I was getting.

The engine has began knocking under any acceleration, the oil pressure is at about 20 or lower and I fear for my engine.

Only things that have been done are oil change and coolant added.

Anyone have any idea what it may be? I have an unemployed "gear head" friend who has offered to do a teardown if necessary but I'm hoping for a simpler fix.

KNYFE · 05-19-2006, 08:18 PM

Current thought is a thrown rod.... *sigh*

Well, this may be the chance to rebuild her... "Stronger... Faster..." or whatever. Guess I'll have time to do the interior work now.

rnoswal · 05-19-2006, 10:11 PM

As a general rule the oil pressure should be 10 for every 1000 rpms, so 20 for 2000 and so on. If it is 20 or lower while driving, a lot of us would say change out the sender for a new one, but if it is rattling then it is time for a rebuild. No cheap way about it, except for labor if you can do most of it. The engine has to come out and almost everything will have to be replaced.

The crank can be ground if it hasn't rattled too much, the rods can be re-used, but you should put ARP bolts in them. The cylinders will probably be worn out and need reboring and new pistons. You may as well get the head done too while it is off. Valve job and probably a few valves or more and maybe even guides.

It will be like a new engine when you finish and it will be worth it. With good maintenance you can get several hundred miles out of it again. Put in a metal head gasket and studs to make sure that doesn't go first. I wish FelPro made good gaskets for these engines like they do for almost every other engine. Not the gray graphite gaskets, but their blue colored performance head gaskets. I have used them for racing a modified and my Toyota Celica with never one problem, but I just don't think they make them.

Good luck and keep us up to date.

Russ

suprra_girl · 05-19-2006, 10:20 PM

stock oil pressure for a 7m is 4.6psi at idle
usually 20 or something when cruising?

and you're sure she's a knockin in the bottom end?

TONY! · 05-20-2006, 02:06 AM

Does it sound like this?
http://www.geocities.com/ma71supratu...h/rodknock.mp3
Keep in mind that a spun bearing can sound differently in different cases, not to mention that sounds in life may sound different than what you would have from recordings and replays.

If you have a spun bearing, you may see shavings in the oil.
That would be one way of diagnosing it; check your oil after you dump it.

Another way of diagnosing it is to remove one spark plug wire at a time to see if the sound goes away or changes greatly. Removing a spark plug will decrease the cylinder pressure and therefore decrease the pressure on the piston, which in turn is tranfered to the rod.

Another way of diagnosing it is to spend a whole ten dollars and buy yourself a mechanic's stethoscope as sold on eBay, then learn how to interpret what you hear.

First do the diagnosing, and then I'll tell you more if need be.

supradaddy0803 · 05-28-2006, 02:49 AM

I had the same problem with my 86.5 and I tore the whole motor down and rebuilt it all cost me like 1500 bucks for all the parts to my supprise that there was no problem with the crank it was still within limits by my handy shop manuel. So I did some checking and found a guy talking about the same thing and he said 7MGE motors are very intollerant of low oil even by the least bit. So this explains the oil pressure being right and the knock check the oil and make sure it is full. Mine does this also but has a leaking rear main seal so when it gets low it is a good tell all it is low. Also check for oil leaks you cant see like from the distributor oil seal with all the air intake stuff in the way it is hard to see if it is leaking thats where the leak on my 86.5 was baffled me never smelled the oil cooking funny I have had a 86.5 a 87 and a 84 only time I have seen that.

rnoswal · 05-28-2006, 12:17 PM

Like Tony said, a stethascope is a great buy to pinpoint noises. Sometimes when removing the sparkplug wire from a cylinder and the noise goes away or lessens by a bit is the wrist pin on the upper connecting rod going bad too. A rod knocking noise increases with engine rpm and is a deep noise and not fixable without pulling the engine.

Any car can run low on oil and still run fine, in fact most cars do use oil and it is not uncommon to have to add a quart or two on older cars, but it is an indication of a leak or oil burning. Any car that lets the oil level get too low and lets air get into the oil pump is going to ruin the engine. The Toyota actually has a very good oiling system and a very good oil pan setup. I know that when I rebuilt my Supra engine and replaced the oil sending unit, I would have around 60 lbs pressure at startup and after warming up in would drop some. But my oil pressure would always follow the 10lbs per 1000 rpms. Although it does drop down to below the 10 lbs at idle when warm, the red low oil pressure light never came on.

You might look at the crank pulley/ vibration dampener as a source of the noise or even an engine or transmission mount the might be hitting the frame while under load, but any mechanic can easily tell you if the noise is a rod bearing. It is a distinctive sound heard very well under acceleration. It is harder to hear at idle unless it is really gone bad.

Try to get someone you can trust to listen to the engine. Don't let just anyone try to make the diagnosis, because an engine rebuild makes the mechanics eyes gleam when thinking about the money that can be made.

Russ

05-19-2006, 06:06 PM	#1
KNYFE 3" Exhaust Join Date: Sep 2005 Location: Willmar, MN Posts: 131	Uh oh... Help? Well, I had my Supra at my car guys shop and he was going to put my new wheels on. We went for a short drive before so he could hear a new noise that I was getting. The engine has began knocking under any acceleration, the oil pressure is at about 20 or lower and I fear for my engine. Only things that have been done are oil change and coolant added. Anyone have any idea what it may be? I have an unemployed "gear head" friend who has offered to do a teardown if necessary but I'm hoping for a simpler fix. __________________ http://www.cardomain.com/id/FastnLowI30 Supra, I30 and A8 are above...

05-19-2006, 08:18 PM	#2
KNYFE 3" Exhaust Join Date: Sep 2005 Location: Willmar, MN Posts: 131	Current thought is a thrown rod.... sigh Well, this may be the chance to rebuild her... "Stronger... Faster..." or whatever. Guess I'll have time to do the interior work now. __________________ http://www.cardomain.com/id/FastnLowI30 Supra, I30 and A8 are above...

05-19-2006, 10:20 PM	#4
suprra_girl 7M POWAH! ;) Join Date: Jun 2004 Location: New Zealand Posts: 2,312	stock oil pressure for a 7m is 4.6psi at idle usually 20 or something when cruising? and you're sure she's a knockin in the bottom end? __________________ Please use the forum to ask your questions as they will get replied to much faster than pming me Pics of my build. "Good girls are just bad girls that don't get caught" Do a diagnostic first!

05-28-2006, 02:49 AM	#6
supradaddy0803 12psi boost Join Date: May 2006 Location: Athens, TX Posts: 308	here is what I have found I had the same problem with my 86.5 and I tore the whole motor down and rebuilt it all cost me like 1500 bucks for all the parts to my supprise that there was no problem with the crank it was still within limits by my handy shop manuel. So I did some checking and found a guy talking about the same thing and he said 7MGE motors are very intollerant of low oil even by the least bit. So this explains the oil pressure being right and the knock check the oil and make sure it is full. Mine does this also but has a leaking rear main seal so when it gets low it is a good tell all it is low. Also check for oil leaks you cant see like from the distributor oil seal with all the air intake stuff in the way it is hard to see if it is leaking thats where the leak on my 86.5 was baffled me never smelled the oil cooking funny I have had a 86.5 a 87 and a 84 only time I have seen that.

05-19-2006, 10:11 PM	#3
rnoswal Lexus & 550's Join Date: Apr 2005 Location: Bossier City LA Posts: 556	As a general rule the oil pressure should be 10 for every 1000 rpms, so 20 for 2000 and so on. If it is 20 or lower while driving, a lot of us would say change out the sender for a new one, but if it is rattling then it is time for a rebuild. No cheap way about it, except for labor if you can do most of it. The engine has to come out and almost everything will have to be replaced. The crank can be ground if it hasn't rattled too much, the rods can be re-used, but you should put ARP bolts in them. The cylinders will probably be worn out and need reboring and new pistons. You may as well get the head done too while it is off. Valve job and probably a few valves or more and maybe even guides. It will be like a new engine when you finish and it will be worth it. With good maintenance you can get several hundred miles out of it again. Put in a metal head gasket and studs to make sure that doesn't go first. I wish FelPro made good gaskets for these engines like they do for almost every other engine. Not the gray graphite gaskets, but their blue colored performance head gaskets. I have used them for racing a modified and my Toyota Celica with never one problem, but I just don't think they make them. Good luck and keep us up to date. Russ

05-20-2006, 02:06 AM	#5
TONY! 12psi boost Join Date: Sep 2005 Location: Troy, NY 12180 Posts: 353	Does it sound like this? http://www.geocities.com/ma71supratu...h/rodknock.mp3 Keep in mind that a spun bearing can sound differently in different cases, not to mention that sounds in life may sound different than what you would have from recordings and replays. If you have a spun bearing, you may see shavings in the oil. That would be one way of diagnosing it; check your oil after you dump it. Another way of diagnosing it is to remove one spark plug wire at a time to see if the sound goes away or changes greatly. Removing a spark plug will decrease the cylinder pressure and therefore decrease the pressure on the piston, which in turn is tranfered to the rod. Another way of diagnosing it is to spend a whole ten dollars and buy yourself a mechanic's stethoscope as sold on eBay, then learn how to interpret what you hear. First do the diagnosing, and then I'll tell you more if need be.

05-28-2006, 12:17 PM	#7
rnoswal Lexus & 550's Join Date: Apr 2005 Location: Bossier City LA Posts: 556	Like Tony said, a stethascope is a great buy to pinpoint noises. Sometimes when removing the sparkplug wire from a cylinder and the noise goes away or lessens by a bit is the wrist pin on the upper connecting rod going bad too. A rod knocking noise increases with engine rpm and is a deep noise and not fixable without pulling the engine. Any car can run low on oil and still run fine, in fact most cars do use oil and it is not uncommon to have to add a quart or two on older cars, but it is an indication of a leak or oil burning. Any car that lets the oil level get too low and lets air get into the oil pump is going to ruin the engine. The Toyota actually has a very good oiling system and a very good oil pan setup. I know that when I rebuilt my Supra engine and replaced the oil sending unit, I would have around 60 lbs pressure at startup and after warming up in would drop some. But my oil pressure would always follow the 10lbs per 1000 rpms. Although it does drop down to below the 10 lbs at idle when warm, the red low oil pressure light never came on. You might look at the crank pulley/ vibration dampener as a source of the noise or even an engine or transmission mount the might be hitting the frame while under load, but any mechanic can easily tell you if the noise is a rod bearing. It is a distinctive sound heard very well under acceleration. It is harder to hear at idle unless it is really gone bad. Try to get someone you can trust to listen to the engine. Don't let just anyone try to make the diagnosis, because an engine rebuild makes the mechanics eyes gleam when thinking about the money that can be made. Russ