Volvo Owners Club Forum - View Single Post - Intermittent fault, possibly crank sensor

Forrest · Aug 17th, 2013, 01:50

The situation became critical following a genuine breakdown on Tuesday with a passing policeman having to direct traffic while my sensor cooled down.

Having read quite a bit about replacing the crank position sensor I came to the conclusion that replacement had to be attempted, but that there was a risk of breaking the bracket it fits into. This was an acceptable risk since this is the grottiest of my 940s; so kill or cure it was. In the event, I could see no evidence of the flimsy bracket. The sensor appeared to fit straight into the bell housing. Did Volvo change the design in later models?

Although daunting because of restricted access and visibility the replacement was actually a twenty minute job and probably came close to being a model installation. So I thought I'd share in case it helps anyone else.

Before starting.

Order a genuine replacement from Rufe. P/N 271949 £34.20
Spray some penetrating oil over the corroded bolt

During surgery

Access is nasty. You have to get your hand through a maze of pipes and cables. It helps to be six foot tall with thin arms.

Yes, you've got to get your arm through there to just below the distributor cap. Tips here are to remove the auto transmission dipstick and unclip and tuck out of the way that smaller hose.

The description in the FAQ involves using various extension bars and a 10mm socket. I first tried to get my small 1/4" socket ratchet in there, but there wasn't enough clearance. I think that's when I broke a piece of plastic off the old sensor bracket.

I had found another article, I think on Turbobricks, that recommended using a 10mm ratchet spanner. I had been meaning to buy one of those all week, but never got around to it. What worked really well for me was a standard 10mm spanner but using it the other way up from normal. It seemed to fit over the curved top of the bell housing and gave me enough room to get the bolt loose. As soon as I could turn the bolt by hand I did so, keeping a firm hold on it all the time. The major no-no here is to drop the bolt into the transmission.

The old sensor came out very easily. Others have reported that they can be stiff. Note that the cable is clipped to the heater pipes in two places. My tip here is to remove the first clip from the cable and the second clip from the pipe, counting along from the 3-pin plug on the firewall. The second clip is harder to see and in my case was clipped to a metal pipe near the engine.

The Volvo kit contains two replacement clips of the correct size. Use the replacement clip no. 2 and attach it to the new sensor cable in the correct place and orientation using the old sensor as a guide. This clip will then be in the right place to attach to its pipe when you have installed the new sensor.

Following advice from the articles I had read I smeared a small quantity of high melting point grease on the outside of the new sensor and over the thread of the bolt to aid future removal. I'm not sure if this will ever be of practical use since I suspect the new sensor will outlive the car, but you never know.

Manoeuvring the new sensor into position is definitely a case of needing eyes in your fingers, but it goes into place quite easily. I found that it was best not to put the bolt through the sensor until it was safely resting in its hole in the bell housing. It is quite easy to feel where to position the bolt afterwards and it reduces the risk of dropping it. Fiddlier is getting the bolt into the threaded hole in bell housing but that didn't take too long. Again, make sure it is firmly screwed in by hand until letting go of it. I was able to screw the bolt nearly fully home by hand and then just nipped it in with a small turn of the spanner, this time using the open end from above.

Although I couldn't see any obvious bare wires, the insulation had definitely gone on my old sensor.

I also took the opportunity when ordering from FRF Motors to get some new 3mm vacuum hose and with the help of one of the parts being distributed by Rod25 last month refurbished my PCV tubing which was held together with friction tape in two places. The old girl is running better than ever now.

Aug 17th, 2013, 01:50	#3
Forrest VOC Member Last Online: Today 22:02 Join Date: Feb 2008 Location: Gloucester	It lives The situation became critical following a genuine breakdown on Tuesday with a passing policeman having to direct traffic while my sensor cooled down. Having read quite a bit about replacing the crank position sensor I came to the conclusion that replacement had to be attempted, but that there was a risk of breaking the bracket it fits into. This was an acceptable risk since this is the grottiest of my 940s; so kill or cure it was. In the event, I could see no evidence of the flimsy bracket. The sensor appeared to fit straight into the bell housing. Did Volvo change the design in later models? Although daunting because of restricted access and visibility the replacement was actually a twenty minute job and probably came close to being a model installation. So I thought I'd share in case it helps anyone else. Before starting. Order a genuine replacement from Rufe. P/N 271949 £34.20 Spray some penetrating oil over the corroded bolt During surgery Access is nasty. You have to get your hand through a maze of pipes and cables. It helps to be six foot tall with thin arms. Yes, you've got to get your arm through there to just below the distributor cap. Tips here are to remove the auto transmission dipstick and unclip and tuck out of the way that smaller hose. The description in the FAQ involves using various extension bars and a 10mm socket. I first tried to get my small 1/4" socket ratchet in there, but there wasn't enough clearance. I think that's when I broke a piece of plastic off the old sensor bracket. I had found another article, I think on Turbobricks, that recommended using a 10mm ratchet spanner. I had been meaning to buy one of those all week, but never got around to it. What worked really well for me was a standard 10mm spanner but using it the other way up from normal. It seemed to fit over the curved top of the bell housing and gave me enough room to get the bolt loose. As soon as I could turn the bolt by hand I did so, keeping a firm hold on it all the time. The major no-no here is to drop the bolt into the transmission. The old sensor came out very easily. Others have reported that they can be stiff. Note that the cable is clipped to the heater pipes in two places. My tip here is to remove the first clip from the cable and the second clip from the pipe, counting along from the 3-pin plug on the firewall. The second clip is harder to see and in my case was clipped to a metal pipe near the engine. The Volvo kit contains two replacement clips of the correct size. Use the replacement clip no. 2 and attach it to the new sensor cable in the correct place and orientation using the old sensor as a guide. This clip will then be in the right place to attach to its pipe when you have installed the new sensor. Following advice from the articles I had read I smeared a small quantity of high melting point grease on the outside of the new sensor and over the thread of the bolt to aid future removal. I'm not sure if this will ever be of practical use since I suspect the new sensor will outlive the car, but you never know. Manoeuvring the new sensor into position is definitely a case of needing eyes in your fingers, but it goes into place quite easily. I found that it was best not to put the bolt through the sensor until it was safely resting in its hole in the bell housing. It is quite easy to feel where to position the bolt afterwards and it reduces the risk of dropping it. Fiddlier is getting the bolt into the threaded hole in bell housing but that didn't take too long. Again, make sure it is firmly screwed in by hand until letting go of it. I was able to screw the bolt nearly fully home by hand and then just nipped it in with a small turn of the spanner, this time using the open end from above. Although I couldn't see any obvious bare wires, the insulation had definitely gone on my old sensor. I also took the opportunity when ordering from FRF Motors to get some new 3mm vacuum hose and with the help of one of the parts being distributed by Rod25 last month refurbished my PCV tubing which was held together with friction tape in two places. The old girl is running better than ever now.