Connecting Rod Bolt Replacement? (1 Viewer)

ratchet

SILVER Star
Joined
Dec 10, 2003
Messages
130
Location
Colorado
The Specifics:
1994 FZJ80
approximately 215,000 miles
serviced at the dealer and babied its entire life
motor completely stock

The Background:
The past few times I started it I noticed that the oil pressure seemed low and then would come up as it warmed up. This is odd and opposite of normal behavior in my experience (usually the pressure is high when cold and comes down a little as it warms up). I had been planning to get a mechanical gauge on it to check it but hadn't gotten to it. On a recent drive (interstate speeds) to a neighboring town, about 45 minutes in I noticed the oil pressure was just below the lowest tick mark on the gauge. I thought that seemed low and out of the ordinary. I watched it for a few miles and revved the motor a bit to see if it would come up with the RPMs but it didn't. Shortly after that the pressure started falling so I got off at the next exit. I got out and looked for leaks but found none and heard no funny noises. If I recall correctly, at idle, the pressure was about halfway between the bottom of the gauge and the first tick mark which is a lot lower than I am used to seeing. I turned it off and let it sit for a minute and then checked the oil level which was fine. I turned it back up and heard a knocking noise right off the bat but then quieted down. I put it in gear and gave it some gas to move and heard a knocking. At this point I shut it down and had it towed to town.

The next day I changed the oil and filter. I had a Wix filter on it and replaced it with a Toyota filter. When I turned it on the oil pressure gauge hit the third tick mark like I am used to seeing but the motor knocked. I used a stethoscope and narrowed it to the middle of the oil pan. Since it seemed like the bearing was just beginning to go I decided to pull the pan and see what it looked like. Once I got the pan off I pulled the connecting rod caps one by one. I found that the third and fourth (if counting the cylinders from the front of the motor) rod bearings were bad. When I was removing the cap for the sixth rod the passenger side nut seemed very loose. Not finger tight but definitely not at proper torque.

I measured all the connecting rod bolts as per procedure and found them all to be within specifications. Even the one with the loose nut, although that one was thinner than the rest. I'm in the middle of replacing the bearings now but when I torqued the cylinder six connecting rod bolt (the one that was loose when I removed it) it wouldn't tighten up.

The Question:
Can connecting rod bolts be replaced with the piston and rod in the block? If so, what is the procedure? I looked through the FSM and can't find anything about actually replacing the connecting rod bolts. All I found is that it says that if the bolts are out of spec they should be replaced as a set (bolt and nut) but doesn't have a procedure for it. I tapped on the rod bolt lightly with a hammer and it didn't seem to move. I also found that the head of the bolt had broken off. If I had to guess, I broke it when I tried to torque it down. As clarification, it didn't break when I did the 90 degree torque, it wouldn't even take the 35 ft lbs initial torque so it must have been pretty weak.

Another question I have is why was the connecting rod nut loose in the first place? I wonder if it would have continued to work loose and then I would have had a catastrophic failure sometime down the road.

tl;dr Low oil pressure; changing connecting rod bearings; one rod bolt wouldn't take the recommended torque and broke; How do you change the connecting rod bolts and can it be done without pulling the piston and connecting rod from the motor?

Richard.
 
Last edited:

ratchet

SILVER Star
Joined
Dec 10, 2003
Messages
130
Location
Colorado
I ended up buying some connecting rod bolts at a Toyota dealership and spoke with the service manager there. He said that the proper procedure for replacing the bolts is to tap them out with a punch and then press them back in.

Since the motor is not torn down this is not an option for my situation. Obviously, I can get to the bottom of the connecting rod so I used a punch to tap out the broken bolt from the bottom. The bolts have an un-threaded shank so I made a few small spacers to take up that space so I could use a nut to pull the bolt in to place. This seemed to work fine but the rotational force of tightening up the nut tended to spin the bolt a little bit as it was sliding in to place. To account for this I had to start the bolt out slightly counter clockwise from where I wanted it to end up.

I measured the bolt thickness before and after. There was very little, if any, difference and it was still well within the specifications. Once the bolt was in place I put the new bearing in and checked the bearing clearance with Plastigauge. Everything was within the specifications so I cleaned it up, put the assembly lube on and torqued it down again. The rod bolts took the torque both times and everything seemed to go together fine. I still have a couple more bearings to go before I can put it back together and fire it up but I wanted to add this before I forgot.

Richard.
 
Joined
Jan 11, 2019
Messages
210
Location
Sacramento
Glad you figured it out and hopefully fixed the issue. I wonder why it happened with only 215k on the engine, taking the reputation of these engines.

Also what kind of oil are you running? I'm running 5w-40 mobil and at 2500 rpm its flat on the second tick mark, and at idle its between the bottom and the first tick mark. Engine seems to run fine without any wacky sounds, 173k miles on the clock. Is my oil pressure to low?
 
Joined
Jan 11, 2019
Messages
210
Location
Sacramento
The Wix filter may have been the cause of your trouble. There is a thread somewhere on here that addresses the WIX filter of death.
I've searched the forum and now I'm nervous lol. I've been using Wix filters all my life because of their quality. I've only done one oil change since owning this truck and the previous filter was a toyota one. I did the oil change because I though the oil pressure was on the lower side but I've read that a lot of people have idle pressure between bottom and 1st tick mark.
I will change the filter with new oil and we'll see if that helps. Thanks.
 

ratchet

SILVER Star
Joined
Dec 10, 2003
Messages
130
Location
Colorado
The reason I got the rod knock is because of the low oil pressure. After I changed the oil/filter the oil pressure gauge hit just over the third tick mark on start up. I did nothing else other than changing the oil and filter so that leads me to believe that the reason for the low oil pressure was the Wix filter. I'd have to go back through my records to confirm but I believe I was running 10w-30 and I'm partial to Mobil 1 usually. While I was sitting on the side of the road waiting for the tow truck I did some searching and found that people have had multiple issues that they believe are caused by the Wix filters. I too have used Wix in the past due to their reputation of quality but in the future I will never put anything other than Toyota on this vehicle.

Regarding the oil pressure level, under normal use I recall it being near the upper tick mark when cold or revving high, somewhere around the middle when being driven normally and near the lower one at idle. The rule of thumb that I've heard is 10 psi per 1000 rpm. I'll probably put a mechanical gauge on it once its back together to verify good oil pressure and try to get an idea of how the stock gauge (which I've heard is pretty inaccurate) is reading.

Now the reason for the loose connecting rod nut and having the connecting rod bolt break...I have no clue. The Toyota service manager I spoke to was surprised and said that they never need to replace them. I have to wonder, if my low oil pressure situation hadn't happened, if that nut would have worked its way loose and there would have been catastrophic engine failure later on. Although I may just be trying to make myself feel better about the whole situation and it may have been fine for many years and thousands of miles.

Richard.
 
Last edited:
Joined
Feb 10, 2017
Messages
1,075
Location
Seattle
I've searched the forum and now I'm nervous lol. I've been using Wix filters all my life because of their quality. I've only done one oil change since owning this truck and the previous filter was a toyota one. I did the oil change because I though the oil pressure was on the lower side but I've read that a lot of people have idle pressure between bottom and 1st tick mark.
I will change the filter with new oil and we'll see if that helps. Thanks.

There are quite a few of us who have had motors die due to wix filters. I bought mine with a thrown rod, tracked it down to a wix filter.

KEEP YOUR FILTER AND CONTACT WIX. If you can prove that their filter caused the issue they will pay to rebuild your motor. Don't cut it open, contact your local wix rep.

WIX thread
 

Users who are viewing this thread

Top Bottom