Where is this plenum?

[BigBus]

I am looking for the plenum to check the drainage but cannot find it. My garage has never heard of a plenum (filled with confidence there). Anyone know of an engine diagram for the old girl (Mark 1 CDT no frills)

[e668ecp]

Lift the bonnet and its just in front of the windscreen. Access to it is via lifting the mesh panels below it and then pull off the rubber seal about half way, take out the windscreen clips but take care as they fly off never to be seen again. Then there is a further panel underneath the mesh sections which slides out. You can then see the plenum. The hole to clear is on the passenger side and if you look down you can see it. A long thin stick is required to poke thro and clear it.

[sf8752]

Then do the mod it is then easy to check the drain


steve....

[Simondi]

If you have a look in the How To section there is a full step by step guide.

[Cymrudragon]

My garage has never heard of a plenum


thats no suprise.........it took my car to get the bumper sorted to a well respected repairer guess what they said ....whooooooo parts are hard to get hold of for a Rover, no they are not i got a list of supplyers as long as arm .......oh and its a ffffffffffffffffffffffffff MG ZT not a fffff ROVER

[Dragrad]

Thread moved to correct forum. Re-direct left in old.

Have a read of this document:-
http://www.the75andztclub.co.uk/down...ile=tid002.pdf

Do you have a sun roof, if so you need to check the drainage channels from that as well.

Prevention is better than cure, so have a look at this little snippet

[T-Cut]

Here's something I prepared earlier for such an occasion.

The Plenum and its Drains

The plenum is a chamber that collects fresh air to feed the interior vents/aircon system. It's located between the firewall at the rear of the engine and the wall which forms the front of the cab section. Air is supplied via the scuttle vents, which run across the body below the windscreen.

Much of the rain and wash water draining from the windscreen also goes into the plenum, so this must be drained off. To do that, the plenum floor has two rubber drain tubes. One is accessible on the near/passenger side, but the second one is positioned under the brake servo and for all practical purposes is not accessible from under the bonnet. These tubes pass through a second panel below the plenum floor, from where they drain onto the ground. From under the car, these tubes can be seen as short, rubber nozzles with a flattened end. The flattened ends are supposed to minimise the ingress of road debris. In practice, they tend to harbour debris which enters them from the plenum. For this reason, they must be cleared on a regular basis.

It's important that the plenum remains dry because it houses the ECU. This is mounted a few inches above the floor on the firewall face. Also vulnerable to flood water is the pollen filter, which is mounted over a large hatch on the nearside of the rear wall. If the lower edge of the filter gets wet, it soon starts to smell and this gets into the cab with the incoming air.

On Mark 1 models, there are two further rubber tubes which drain the upper plenum area. These are located on the upper front wings, near the bonnet hinges. On Mark 2 models (and some late Mark 1s), the driver's side drain is plugged off. This is because the drain is actually too high for water to enter and is therefore redundant. The upper drain tubes are similar to the others and have a flattened nozzle, which directs water onto the back of the wheel arch liner. From here, it runs onto the ground. An MGR service bulletin suggests that the flat nozzel should be trimmed to a 45° angle to improve drainage. Whether this is worth doing is a matter of opinion. Regular clearing of the tubes with a cane, etc. is the better strategy.

The official service schedule advises that the lower drains should be cleared every 15,000 miles/annually. In reality, this is not often enough. As a minimum, they should be rodded through on a monthly basis. If the car is parked under trees or during particularly wet weather, rodding should be even more frequent. Failure to keep the plenum dry may cause flooding of the front passenger footwell as water enters the cab via the pollen filter hatch. It may also allow the ECU to become wet/submerged, leading to unpredictable issues with the electronic systems.

Accessing the drains and rodding them through is well documented elsewhere. In practice, it's sufficient to clear the only accessible tube on the nearside of the plenum floor. This can be made much more convenient by making a rodding hole in the water shield which lies under the grill panel. The hole should be filled with removable grommet. Then, only the grill and grommet have to be removed to clear the drain. This modification is also described in detail elsewhere. To clear the driver's side floor drain requires you to raise the car on ramps so you can prod out any debris using a thin wire. This is not really necessary if the nearside drain gets regular attention.

This post has my quick find marker: #plen#