4200 oil pressure sender removal

conaero

Forum Owner
Messages
34,593
Many thanks to Dave Harris for his very detailed and excellent how to.

You can also replace the sender without removing the plenum with a crows foot spanner but its a very tricky job. The home mechanic would be advised to approach it in this method observing safety and making sure you don't drop anything into or down the engine.


REPLACING THE OIL PRESSURE SENDER 4200 ENGINE



Remove the rear plastic strip from engine bay.

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Release fuel rail supply on both sides. Beware that there may be residual fuel pressure so crack open gently. Obvious, but has to be said DO NOT ATTEMPT WITH HOT ENGINE !

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Release fuel rail cover both sides, not totally necessary but it gives a slightly better view of the manifold nuts..

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Pull back fuel supply hoses and tie up so they don’t drip and release servo vacuum hose from manifold. Lift off fuel injector rail covers.


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Press clips on injector electrical connector and pull down. Be careful that the white “gasket” inside the connector does not drop out. Repeat on all 8 injectors.

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With a 10mm socket and extension bar gently and equally release tension on all the manifold to cylinder head nuts. Best to use a 3/8 drive (or less) socket as some of the nuts have limited space around them. Be sure to slip your finger under the socket as you lift it off, as the nut will drop out of the socket and there are so many places for it to hide in and around the engine bay.

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Release the clip holding the supply pipe at the front left of manifold.

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Release the 4 socket headed bolts at the throttle body flange or release the clip between the body and manifold. Unless you have the special tool the standard clips (Oetiker ?) are a pig to re-connect. It is better to lift the nearside cover to gain access.

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There are 4 socket headed bolts (5mm Allen key) and they don’t come right out as they are trapped in place by the inlet rubber so they need to be released equally until they are all free. There is one awkward one but a ball ended key gave access ok.

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At this point the manifold will lift off but is connected by a number of vacuum hoses.

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Disconnect the vacuum hose clips, across the bulkhead, where they restrict movement and at the front left cylinder head.

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It is now possible to lift and pull the manifold far enough forward to access the sender unit.

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Take the precaution of covering the inlet ports now that they exposed. There is every opportunity for nasty gribblies, washers, nuts, anything that may be dropped - won’t fall on the floor. No matter how obscure the trajectory, it WILL find it’s way onto the piston crown. Don’t let that happen. Cover the ports immediately.

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There is the little blighter, at the rear of the engine block, just in front of the opening in the bell housing.

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Release the cable clamp and pull the cable away. Cover the opening in the bell housing or you know what will happen to the cable clamp nut ! The hexagon on the sender is now just about discernable with a finger.

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It takes about an hour to get this far. Using a 24mm crows foot spanner the idea is to slip it under the sender onto the hexagon, a quick flick of the wrist and it’s undone. Well this is where it starts to get difficult. There is a sensor that appears to run off the flywheel that stands proud right under where the spanner needs to fit. Along with the cables that pass nearby it’s very frustrating trying to find the flats for the spanner to fit. The sensor won’t come up and out of the way as it collides with the underside of the pressure sensor. If it frustrates - walk away and try again later. I tried a vertical strap wrench but it just crushed the casing. With the help of a friend we managed to get the crows foot in place and with a torque bar it went of CRACK . This bit took about 6 hours. No amount of advice will help here, just keep trying everything and try some more, walk away and take the dog out or try again the next day. It took two of us, one holding the extension bar in the spanner and the other with a long bar applying the rotary motion before we could get any movement.

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This the obstructive sensor cable.

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The strap clamp.

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The old sensor.
The new sensor went in ok but no way could we get the crows foot on it so we made our own from an open ended. Anti corrosion grease was applied to the electrical connection.

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The metal is pretty tough but with a hacksaw, bench drill and file you can get the thing you need. The advantage is that the open ended spanner is cranked so you can turn it up the other way to reposition it. The crows foot is “straight in” and so if the flats aren’t lined up you are stuffed.

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Assembly is the reverse of everything but don’t forget all the hose clips, check the seals are in the injector plugs and ease the manifold very gently down by evenly turning the nuts. Another hour to re-assemble.


Finishing notes.
It is suspected that when the sender is removed the oil in the accumulator (under the manifold) drains down. Consequently upon start up it does take time for the oilways to fill and pressurise. So don’t panic (like I did !) when you first start up. It will rattle and shake until after maybe 20-30 seconds everything will quieten down and smooth out. If it doesn’t feel free to panic !!

The oil pressure gauge now performs as it should, so it was worth the wounds, frustrations and frights.

I don’t think it would be worth attempting without removing the manifold. There just isn’t enough room around the sender.

More info on the new sensor it reads 10ohm at atmospheric, about 40ohm at 2 bar and about 80ohm at 5bar allowing for the course accuracy of my compressor pressure gauge.
 

conaero

Forum Owner
Messages
34,593
Just a not on restarting a car/priming the oil system.

Its advisable to turn the car over without it starting in 15 second bursts so prime the oil system.

The engine can be disabled from firing in may ways to do this but probably the easiest is to remove the wires to all 8 coil packs. The oil light on the gauge should go out when enough pressure has been reached.
 

Klive

Junior Member
Messages
724
Is it necessary or even possible to bleed the fuel rails after reconnecting?

Edited after starting the engine.
The answer is it's not necessary.
 

CatmanV2

Member
Messages
48,547
Wouldn't have thought so. Any air is simply going to get pumped into the cylinders where it will fail to ignite.
C
 

CatmanV2

Member
Messages
48,547
Figures. Only think I can think is that you'd be pumping (some) unburnt fuel into the cats, but they'd be cold, so I really can't see any issues.

Back and running, mate?

C
 

Todd0987

New Member
Messages
1
Ok I mean no disrespect but................ This job can totally be done without removing the manifold or really much else.
Just saying :capricorn:
 

philw696

Member
Messages
25,114
You need very small girly hands to do it that way.
The joy of removing the manifold is that you can clean the valley out of the detritus that gets in there which cold be a potential fire risk.
Phil.
 

CC4200

New Member
Messages
297
Autoshield charged me £120 labour for replacing mine, well worth it in my opinion !




Paul
 

ahvlanico

Junior Member
Messages
185
hello
Removed mine today and I did not want to remove the manifold so did this.
I bent a 24 key (on the picture it is a 22 but modified to 24mm.clef[1].jpgIMAG4055[1].jpg
 

philw696

Member
Messages
25,114
Just my opinion having done a couple now I like to take the manifold off and give everything a good clean out in the valley as they can be potential fire risks with all the stuff that gets down there and the manifold comes off easily.
 

Zep

Moderator
Messages
9,110
A fair point, I haven't looked under my manifold, I might put my camera under there to see what sort of state its in. :)

Just my opinion having done a couple now I like to take the manifold off and give everything a good clean out in the valley as they can be potential fire risks with all the stuff that gets down there and the manifold comes off easily.
 

maschip

New Member
Messages
7
You folks are awesome! After reading about the process I am voting to have the shop do it. Thanks for your great clarity!
Chip