Inlet air temp sensor retention in air box

[Dave McCulloch]

A quick question to either put my mind at rest or increase my worry levels....

I was giving my 7 a check over before a track day next week, and noticed the inlet air temp sensor dangling.  I'm running jenvey throttle bodies with the Bernard Scouse airbox - the IAT sensor goes through a hole in the backplate.  However, I can't remember now how it was secured.  No nut fell out of the airbox when I removed it,   I've tried to use a torch to look down the throttle bodies to see if one's got caught on top of a valve, but can't see one - though I can't see all the way round the valves.

I'm assuming the engine hasn't ingested the nut as I'd know about it - it would have been a 10mm nut.

Having looked on the DVA website, Dave Andrews recommends using a die to cut a 10mm thread on the sensor (don't know what thread it was as standard) and then using an M10 nut with loctite to secure - which is what I've now done.  But I'm now paranoid where the old fixing's gone - and equally the damage the new fixing could do if it goes AWOL too.

Thanks

Dave

[Graham King]

Dave, I can't look now but I have exactly the same setup as you so can have a look tomorrow night for you if no one else responds in the meantime. 

Graham.

[Paul Deslandes]

One method is to use a grommet with the sensor pushed through.  Nothing to fall into the engine.

I found that mounting the sensor directly to the filter back plate led to the sensor getting hot by conduction and giving a seriously higher temperature reading to the ECU than was really the case.  Maybe the airbox has an insulating backplate, in which case this might not be a problem but mine was showing 50deg when the air temp was closer to 20deg.

[Dave McCulloch]

Thanks both.  Paul, I think I'm going to adopt the grommet method - I'm uncomfortable having a non captive nut inside the airbox.

Dave

[oilyhands]

The grommet method should be just fine, although these have been known to get sucked into the airbox.

When I fit them, they go in with an M10 nut and permanent loctite , I would be utterly amazed if a nut could be shed when properly tightened and with that applied. I havent seen heatsoak as a problem so far and I have fitted a couple of hundred at least.

Oily

[Dave McCulloch]

Thanks Oily.

Can the nut ever be removed after using permanent loctite (or do these sensors never fail), and what is the part No. / reference for permanent loctite?

Thanks

Dave

[Paul Deslandes]

I was quite surprised by it too.  I was running a laptop as a datalogger on the MBE ECU output for curiosity as much as anything else and was amazed to see the apparent air temperature up at about 50degC.  As it was a normal spring evening this seemed somewhat unlikely. 

The sensor was mounted to the ITG sausage filter ali back plate which, in turn, is hard mounted between the trumpets and the throttle bodies, so I can only assume it was heat soak.  When cooled down the sensor read the correct air temperature so I don't think it was faulty.  Its now mounted away from the intakes and engine block to better reflect ambient air temperature.

Paul

[ECR]

Mine's mounted on a pop rivetted bracket to the back of the drivers footwell using a grommet to fix it. That way there's no possibility of anything getting sucked into the engine and it also avoids any possibility of heat soak.

[oilyhands]

It can be removed, but it isn't easy. The stuff I use is Loctite 648, there are plenty of alternatives.

Oily

[Paul Deslandes]

Just to clarify the grommet fixing method:

The grommet is fitted into a correctly sized hole in the back plate and the sensor pushed through it from outside.  This should force the grommet to seat correctly into the plate hole and remove any risk of it being sucked into the engine.  The alternative would be to use the grommet just pushed onto the sensor end from inside the box, which I would not recommend.

My sender is fixed exactly as ECR descibes.