Knock Sensor Replacement and Repair

Knock Sensor Replacement
1998 Volvo V70 GLT
1. Disconnect Neg. Battery Terminal
2. Disconnect fuel feed and return lines at rear
of the engine
The Haynes manual shows a fitting for both the feed and return lines, but I only had one
for the feed line. I disconnected the return line at the hose union next to the firewall. The
view on the right shows both lines disconnected. Be ready for a small amount of
leakage with a few shop rags.
3. Disconnect fuel line clamps at the rear and
top of the engine
Removing these clamps is fairly straightforward.
4. Disconnect Fuel Injector Feed Line
Use a 17mm open end wrench.
5. Disconnect Accelerator Cable
First, remove the cover from the accelerator cable bracket, remove the cable
clamp, pull back on the cable cover to lift the cable through the cable bracket slot,
then slowly release the cable. Note the position of the cable end in both pictures.
5. Disconnect Accelerator Cable (cont.)
Finally, disconnect the cable from the cable drum. I saw no transmission
dropdown cable. Note the cable cover off to the side.
6. Disconnect the Injector Electrical Connectors
Remove the electrical connector from each injector on the fuel rail. Remove the
fuel rail cover for more room. The wire loom is in bad shape, I’m going to order a
new one. I wrapped some electrical tape as a temp fix.
7. Remove the Fuel Rail
Remove the fuel rail mounting bolts and carefully wiggle the fuel rail loose from the
intake manifold. When you order the knock sensor, order a new intake manifold
gasket and new o-rings for the 5 injectors. After replacing the o-rings, smear them
with silicone grease before reinstalling the fuel rail. Check the Haynes manual for
mounting bolt torque and position tightening info.
7. Remove the Fuel Rail (cont.)
This view shows the intake manifold without the fuel rail. There was a lot of dirt
and debris around the fuel ports. I used a vacuum cleaner to get rid of it. The
spark plug cover has to come off to route the crankcase ventilation hose through
Ports 2 and 3 when lifting the manifold off the head.
8. Disconnect Turbo Inlet Hose
Loosen the hose clamp and remove the turbo inlet hose from the throttle body.
While there, disconnect the idle air control valve connector (shown removed), and
the throttle body connector on the bottom of the throttle body.
9. Disconnect MAP Sensor Hose and Idle Air Control
(IAC) valve lower hose
Disconnect the Manifold Air Pressure sensor hose from the hose union, and
disconnect the IAC lower hose.
9. Disconnect MAP Hose and Idle Air Control Valve
(IAC) Lower Hose (cont.)
This view shows the manifold hose union without the MAP sensor hose with the
IAC lower hose disconnected. I numbered the hose and hose union with a piece of
masking tape to remember where it went. Once the IAC lower hose is removed,
you can tie the turbo inlet hose back out of the way.
10. Throttle Body View
This view shows the turbo inlet hose and throttle cable removed from the drum,
with the IAC valve and throttle body connectors disconnected.
11. Manifold Vacuum Hoses
This view shows three of four vacuum connections connected to the intake manifold. The Haynes manual
describes them as the as A. Inlet Air Temperature Control Valve, B. MAP sensor, C. Brake Servo
I don’t think the manual is correct, but I removed and numbered only A and B. The brake servo hose
connector (C.) was very difficult to reach, but was long enough that I could remove the manifold without
disconnecting the hose. Disregard the X’d out connection. You removed it already in Step 9.
12. Disconnect Transmission Dipstick Standoff
and Intake Manifold Lower Support
For me, this was one of the hardest things for me to do. There is not a lot of
room to work in this area
• There are two bolts under the manifold that have to come off. One secures
the dipstick to the manifold. It installs vertically and easy to get to from
under the car. The other is a vertical bolt which connects the manifold to a
support fitting. This one is nearly impossible to reach with regular hand
However, the support bracket connects to the engine block with a horizontal
bolt. Use a long extension from the front of the car to reach it. Leave the
fitting attached to the bottom of the manifold. There is also a wire support
bolted to the block through the fitting. Remove it too. I started the
reinstallation of both bolts from the top of the car, then tightened them from
under the car.
These bolts are a PITA, but once you get them off, you almost have the
manifold off.
13. Remove Intake Manifold
Follow the instructions in the Haynes manual for loosening the intake manifold mounting
bolts, then lift the manifold off the head. You have to feed the crankcase ventilation hose
through ports 2 and 3. Remove the oil separator vacuum hose from the fitting on the right
side of the manifold as you lift it off the head. I saved the hose clip. The circled area is
the manifold support that bolts to the block. I just propped the manifold up inside the
engine compartment out of the way. Be careful not to bend or damage any components.
14. Replacing Knock Sensors
Time to finally replace the sensors. With the manifold in the upper right corner, this view
shows the front of the block with the 10 intake valves, the oil separator (A), and associated
hoses. The rear knock sensor is also visible (B). Remove the forward hose from the oil separator
to reach the forward knock sensor (C).
14. Replacing Knock Sensors (cont.)
This view shows the end of the oil separator hose that connects to the right
side of the intake manifold. Try to save the hose clip
14. Replacing Knock Sensors (cont.)
Remove old front and rear sensors. Install the new front sensor with the
connector in the 3:00 position. Install the new rear sensor with the connector in
the 5:00 position. Follow the Haynes manual for their torque settings.
(Interesting location for the starter – behind the intake manifold…wow!)
14. Replacing Knock Sensors (cont.)
When installing the new sensors, route the new harness as with the old sensors.
This view shows the sensors’ connector on the subframe, forward of the starter.
The Haynes manual is invaluable, use it. It rates the job as “fairly difficult.” I’d
agree. I’m no expert, I would rate my skill as Level 2 as per the IPD catalog.
What a feeling of accomplishment when the car started and ran perfectly on
that first key turn, and the CE light went out!
Keep track of your parts and use a torque wrench during reassembly in reverse
Take your time - work safely.
I saved each hose clamp I cut off and took them to the store to size new screw
type clamps to make sure I had the exact number I needed.
The job took me about 9 hours because I wasn’t familiar with it, but I could
probably do it a lot faster a second time.
I kept $650 in my pocket, not in the Volvo service department’s bank account.
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