Bad knock after 1.5-2 hours of driving.

BlurrSpeed

Member
Joined
Nov 26, 2012
Location
Blue Ridge, Texas
TDI
1997 Passat
A little background. About 3 years ago I decided to put a new (to me) engine in my 97 Passat. The Passat engines were a lot more expensive than the Jetta TDIs & from the research I did they are about the same. It seems to work OK.

The biggest issue I had was it was down on power & will go into default mode which is like it has a clogged EGR/intake or the MAF was bad. That was not the case as the intake was spotless due to a water leak in the EGR cooler. I tested the MAF &computer wires & even replaced the MAF. Not the issue. Anyway Im living with that.

On to my real issue. On the Hi-Way after about 1.5-2 hours of driving, not hard 60-65 MPH, the engine will start knocking. Scary bad. It has done this on 3 trips in several months. It is RPM variable but has nothing to do with power or throttle position. Meaning sometimes it will knock at 45 MPH & 70% throttle or may be 40% @ 65 MPH. I have not been able to vary the throttle or speed to completely eliminate it. I just have to drive until it stops or is not so bad. There is no noticeably performance loss. It also does not change with gear shift, other than the RPM difference, so I dont think its the trans
This last time after about 30 minutes of me wondering when a rod was going to come visit me I pulled over in a Rest Stop, turn it off & let it sit for ~20 minutes. That was a mistake. Before I got back on the HI-Way it was knocking even worse. This lead me to believe sitting the engine heat soaked something that worsened the issue.

Another 20-30 minutes & I pulled off the Hi-Way into a parking lot to see if I could tell what was going on. It of course does not knock at idle or usually below 30 MPH so I got nothing. This was about 5 minutes sitting at idle when I drove around the lot & things seemed OK. Out on the Hi-Way the knock is there but less.

In all cases I never have performance issues & the next day it drives just fine.

I have heard rod knock & a bad fuel pump knocking & thats what it sounds like however I have never seen either go away once they start. It does not sound like the piston slap I have listened to on YouTube & from what I have read slap happens more on cold engines.

This is my daily driver to work 1-1.5 hours in city or Hi-Way rush hour traffic & even after those 3 trips it does not drive any different than it did before. No knock in the city.

It has the stock 5 speed trans with 206K miles & the engine reportedly has about the same.

Does anyone have any idea from my description what this could be? Would a pump going out not knock all the time?
 

Carlos_TJ

Veteran Member
Joined
Aug 3, 2014
Location
Tijuana Mexico
TDI
2009 Bora (BXE PD)
A grossly leaking injector can leak fuel even when not commanded to (like when the piston is traveling up) causing the knock via pre ignition.

Either way, you should not drive the car until you find out what is wrong with it.
 

BlurrSpeed

Member
Joined
Nov 26, 2012
Location
Blue Ridge, Texas
TDI
1997 Passat
Flywheel: If I recall it looked like a regular FW. From what I have read it should have the same clutch setup as the VR6.

Injectors: Never thought thought of that. I would think that would cause a performance hit. I have not checked the spray pattern on the injectors since I put the engine in so I will do that & check for leaks. I also have the original injectors that I could swap out & see if there is a difference.
 

BioDiesel'

Well-known member
Joined
Sep 15, 2013
Location
CT
TDI
1998 Jetta Elsbett single-tank, 230K WVO miles
A couple weeks ago I had an similar engine knock that was caused by a sticking injector on my F-250. But it was also accompanied with a sudden rough idle and large increase in grey exhaust smoke, which differentiated it from a pure mechanical problem. FWIW, the advice from the F-250 guys was to put in in gear and coast down a long hill. If it didn't knock ( while no fuel delivered ), it was a sticking injector.

I hope you find them problem.
 

BioDiesel'

Well-known member
Joined
Sep 15, 2013
Location
CT
TDI
1998 Jetta Elsbett single-tank, 230K WVO miles
For HA-HA's, put a can of Diesel Purge in the fuel filter, run it 45 seconds and let it sit overnight.
 

BlurrSpeed

Member
Joined
Nov 26, 2012
Location
Blue Ridge, Texas
TDI
1997 Passat
I wish I had thought of the sticking injector while it was knocking. I could have done the coast test. Im sure I did but dont recall the results.
 

Lug_Nut

TDIClub Enthusiast, Pre-Forum Veteran Member
Joined
Jun 20, 1998
Location
Sterling, Massachusetts. USA
TDI
idi: 1988 Bolens DGT1700H
Is it really RPM variable or is it road speed variable? 65 mph at 40% in 5th is the same pitch and frequency as 4th at that road speed? (yeah, 'load' is less at higher 4th gear rpm, but for possible cause elimination it'll do).

Motor mount, exhaust against sub-frame, there are a few non-engine, not-too-expensive possibilities so be hopeful.
The A3/B4 1Z/AHU came with single mass flywheels. It'd be dual mass only if someone changed it.
 

BlurrSpeed

Member
Joined
Nov 26, 2012
Location
Blue Ridge, Texas
TDI
1997 Passat
Update/Correction/Solution:

I got the chance to do some testing coming back from a trip the weekend before Thanksgiving. Also Monday & Tuesday going to work. I noticed that I could make it knock on deceleration especial in 3rd gear. It also seemed to get worse turning right & when I was turning left it was less.

Wednesday night I got a flashlight & the floor jack & took a good look. I finally notice the grease on the oil pan & the inner right CV boot spit in half. I could move the right half shaft just a little but the left not at all.

Thanksgiving morning I ordered a new half shaft & put it in that weekend. Monday on the way to work there was no knock. Problem solved.

Interesting thing is I have never heard a CV joint sound like that. I have had two outers go out in a 1985 Sentra & one other car but they never lasted more than 100 or so miles once they started clicking. Im interested to see what the ball bearings & cage look like. Covered in grease they look to still be good but I will wait till the weather is better to clean the grease off & take a look.
 

BioDiesel'

Well-known member
Joined
Sep 15, 2013
Location
CT
TDI
1998 Jetta Elsbett single-tank, 230K WVO miles
thanks for the update, glad you got it fixed relatively easily. good work!
 

vk_bigTDI

Veteran Member
Joined
Dec 15, 2007
Location
CH, CA
TDI
2004 Jetta TDi
I realized you fixed Orc but it has been my thing for past 120.000 , I just did my 3rd axle. Idk why, but for some reason only one side does that to me.

Cheers


Sent from my iPhone using Tapatalk
 

BlurrSpeed

Member
Joined
Nov 26, 2012
Location
Blue Ridge, Texas
TDI
1997 Passat
I originally had to replace the axle because I hit a fence post & broke the outer CV joint. I replaced it with a used one which probably cost as much as the new one I just got. This last one was replace when the inner joint went out most likely due to the boot cracking & the grease coming out. From what I have seen these CV joints are pretty robust.

FYI my replacement was a new Duralast from AutoZone. It was half the price of a new boot kit so I figured it was worth the money plus I would not have to mess with removing, cleaning & replacing the joint assuming it was still usable.

BigTDI - You might check for a bent A frame or other miss alignment.
 
Last edited:

Drivbiwire

Zehntes Jahr der Veteran
Joined
Oct 13, 1998
Location
Boise, Idaho
TDI
2013 Passat TDI, Newmar Ventana 8.3L ISC 3945, 2016 E250 BT, 2000 Jetta TDI
I realized you fixed Orc but it has been my thing for past 120.000 , I just did my 3rd axle. Idk why, but for some reason only one side does that to me.

Cheers


Sent from my iPhone using Tapatalk
After market axle and you NEVER re-installed the balancing donut that was on the original shaft!

This will cause a failure of the shaft and you will keep damaging the shafts until you install the OEM donut.

Its the Passenger side that keeps failing... Right?
 

vk_bigTDI

Veteran Member
Joined
Dec 15, 2007
Location
CH, CA
TDI
2004 Jetta TDi
After market axle and you NEVER re-installed the balancing donut that was on the original shaft!

This will cause a failure of the shaft and you will keep damaging the shafts until you install the OEM donut.

Its the Passenger side that keeps failing... Right?

No, passenger is fine, but driver side. Driver side is the one that keeps failing every 35-40k miles


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