[bassman]

After buying this 160k car with no service history, I expected to see my ECU floating in the plenum chamber, so was pleasantly surprised to see it dry in there, the hole perfectly clear, and only the odd dry leaf....I had a bit of bother getting the wiring harness out of the way, but managed using a broomstick, coming in from the drivers side, and the only route it can take, takes it straight to the plenum drain, so with a few gentle pushes, it moved the harness under the ECU....

I didnt manage to find the drain on the driver side, but wonderd why there was a rubber bung in each of what looked the higher drains....

I poured some water in and it came straight out.....but not out of the tubes i expected it to come from...in fact it didnt even wet them.

When i pushed a piece of 15mm plastic pipe dow the drain, it came out virtually on top of the steering rubber gaitor.....so where have my pipes gone, and does this have to be rectified, or is it ok just running straight through onto the rubber??....

One error I made...I was just about to go into the house to get some parcel tape, to put over the scuttle clips(to avoid losing them), when i pulled a little bit to hard and two of them shot off, luckily one landed behind me, but the other must have fallen in the engine compartment, possibly never to be seen again....(You live and learn)

The modification was easy, found an inch grommet and just heated up an inch hole cutter(easier than finding its other bits and putting in drill etc), and burnt a hole through it......with the pipe not being on the bottom of the drain, i can now see daylight through the mod hole, and see that the drain is clear......another easy job...but only because it was so well documented on here......

Thanks to all who contributed to "Plenum drain cleaning" threads....

2 jobs in 2 days.......I'm on a roll...

 

[T-Cut]

The rubber drain tube for the plenum floor beneath the ECU MUST be in place. It prevents water draining into the closed cavity that separates the plenum from the floor pan. The tube goes through a second 'floor' beneath the plenum floor. The tube seals both holes from seepage. Water just dribbling out of the plenum hole will cause corrosion within the inaccessible cavity. Refitting this tube can be tiresome and requires access from the top and below.

On facelift (Mk2) models, the upper drain near the driver's side bonnet hinge is blanked off. The original drain served very little purpose because it's too high for water to naturally drain through it.

TC

 

[ZTTJim]

The rubber drain tube for the plenum floor beneath the ECU MUST be in place. It prevents water draining into the closed cavity that separates the plenum from the floor pan. The tube goes through a second 'floor' beneath the plenum floor. The tube seals both holes from seepage. Water just dribbling out of the plenum hole will cause corrosion within the inaccessible cavity. Refitting this tube can be tiresome and requires access from the top and below.

On facelift (Mk2) models, the upper drain near the driver's side bonnet hinge is blanked off. The original drain served very little purpose because it's too high for water to naturally drain through it.

TC

Yeah know what you mean about the tube TC, by push too hard I managed to push the tube straight through! What a biatch to pull back through, did it though..... just.

Jim

 

[bassman]

The rubber drain tube for the plenum floor beneath the ECU MUST be in place. It prevents water draining into the closed cavity that separates the plenum from the floor pan. The tube goes through a second 'floor' beneath the plenum floor. The tube seals both holes from seepage. Water just dribbling out of the plenum hole will cause corrosion within the inaccessible cavity. Refitting this tube can be tiresome and requires access from the top and below.

On facelift (Mk2) models, the upper drain near the driver's side bonnet hinge is blanked off. The original drain served very little purpose because it's too high for water to naturally drain through it.

TC

Thanks for this advice, when I look at the drain from the plenum, I still see rubber on the top of the drain, if the tube had been completely pulled through, would this not just be bare metal, I am wondering, rather than being pulled through, whether it has been cut off..
Ive got no ramp access, and am too big to get under....but might be able to feed something up the tube from the side of the car, hoping to see if the other end has been cut...or with a bit of luck, might be able to fish it out from the steering gaitor area...and then pull it back up the drain...unless theyve been cut of course...

Where does the drain tube on the underside of the drivers side initiate from...

 

[BIG 'G']

Rubber tubes

Anyone know where i can get these rubber tubes from and how much they cost as all mine are missing

 

[T-Cut]

when I look at the drain from the plenum, I still see rubber on the top of the drain, if the tube had been completely pulled through, would this not just be bare metal, I am wondering, rather than being pulled through, whether it has been cut off.

I thought you said the pipes were missing from the plenum floor drain, but if the rubber flange is visible around the hole, it's probably OK. I can't see anyone cutting the tube off under the floor.

...or with a bit of luck, might be able to fish it out from the steering gaiter area...and then pull it back up the drain...unless theyve been cut of course...

If the tube were missing from the plenum floor there's no way to retrieve it. It's either been pulled through from above or below and lost, or it's fallen into the floor cavity and lost.

Where does the drain tube on the underside of the drivers side initiate from...

It's beneath the brake servo. For all practical purposes you can't access it from under the bonnet. (Yes I've read about the contortionist approach and a length of twirly wire, but for most of us it's inaccessible and not worth worrying about).

The lower drain tubes may still be available new. Rimmer's listing is a bit confusing because it refers to the upper and lower tubes as if they are the same item. The original upper wing tube (200mm long ) seems to have been superceded by a shorter version with an open tubular end. See this for more: http://www.rimmerbros.co.uk/Item--i-GRID001828

TC

 

[BLADERUNNER954]

On facelift (Mk2) models, the upper drain near the driver's side bonnet hinge is blanked off. The original drain served very little purpose because it's too high for water to naturally drain through it.

TC

thats wierd, mines a Mk1 and the drivers side drains been blanked off with a rubber cap

 

[T-Cut]

thats wierd, mines a Mk1 and the drivers side drains been blanked off with a rubber cap

All Mk2 and later Mk1s (2003-on) have the blanked upper drain. It was done in the Project Drive excercise which started just before the facelift was introduced.

TC

 

[bassman]

I thought you said the pipes were missing from the plenum floor drain, but if the rubber flange is visible around the hole, it's probably OK. I can't see anyone cutting the tube off under the floor.

If the tube were missing from the plenum floor there's no way to retrieve it. It's either been pulled through from above or below and lost, or it's fallen into the floor cavity and lost.

It's beneath the brake servo. For all practical purposes you can't access it from under the bonnet. (Yes I've read about the contortionist approach and a length of twirly wire, but for most of us it's inaccessible and not worth worrying about).

The lower drain tubes may still be available new. Rimmer's listing is a bit confusing because it refers to the upper and lower tubes as if they are the same item. The original upper wing tube (200mm long ) seems to have been superceded by a shorter version with an open tubular end. See this for more: http://www.rimmerbros.co.uk/Item--i-GRID001828

TC

No, I didnt say they were missing(sorry for confusuion)...I said "with the pipe not being on the bottom of the drain, i can now see daylight through the mod hole,".....they are both visible hanging down(complete with loose caps on) under the car.....but there isnt one connected to the n/s plenum drain, as i can see the ground when i look through the drain......and when i poured water into the o/s plenum...it just seemed to fall straight through, none of it coming out of either of the drain tubes....

Ive looked again today(yesterday) and it certainly looks like the n/s one has been cut, because theres still rubber around the top of hole, altho i cant see whats going on below this....

Mines a 2001, and both the high drains have been blanked off......

 

[julienhoulton]

drain

No, I didnt say they were missing(sorry for confusuion)...I said "with the pipe not being on the bottom of the drain, i can now see daylight through the mod hole,".....they are both visible hanging down(complete with loose caps on) under the car.....but there isnt one connected to the n/s plenum drain, as i can see the ground when i look through the drain......and when i poured water into the o/s plenum...it just seemed to fall straight through, none of it coming out of either of the drain tubes....

Ive looked again today(yesterday) and it certainly looks like the n/s one has been cut, because theres still rubber around the top of hole, altho i cant see whats going on below this....

Mines a 2001, and both the high drains have been blanked off......

I have a 2001 connie and all drains are still open to the road

Julien

 

[T-Cut]

.....they are both visible hanging down (complete with loose caps on) under the car.....

The long tubes with flap seals are the aircon condensate drains. The plenum floor drains are much squatter and have flattened nozzles. You have to get right underneath the car to see them. Impossible to spot from the side of the car.

but there isn't one connected to the n/s plenum drain, as I can see the ground when i look through the drain.....

The plenum tubes have a 1 cm rubber flange which seals them in the hole. You wouldn't normally see the ground through one because of the flattened lower end, but some people cut the flattened bit off so it's a free view right through. Same with the upper tube/tubes on the wing.

...and when I poured water into the o/s plenum...it just seemed to fall straight through, none of it coming out of either of the drain tubes....

It will do that OK, but it won't run out of the pipes you mentioned (aircon drains)

Ive looked again today(yesterday) and it certainly looks like the n/s one has been cut, because theres still rubber around the top of hole, altho I cant see whats going on below this....

I suspect the tube is there but has been modified to give free flow. You need to get underneath the car to check. The nearside drain is located on the floor near where the fuel lines run front to back.

Mines a 2001, and both the high drains have been blanked off......

The nearside one (near the bonnet hinge) should be present. The offside one is redundant. Maybe someone has made the nearside one redundant too. Are you sure it's not just blocked solid with rotting leaf gunge?

TC

 

[bassman]

The long tubes with flap seals are the aircon condensate drains. The plenum floor drains are much squatter and have flattened nozzles. You have to get right underneath the car to see them. Impossible to spot from the side of the car.

The plenum tubes have a 1 cm rubber flange which seals them in the hole. You wouldn't normally see the ground through one because of the flattened lower end, but some people cut the flattened bit off so it's a free view right through. Same with the upper tube/tubes on the wing.

It will do that OK, but it won't run out of the pipes you mentioned (aircon drains)

I suspect the tube is there but has been modified to give free flow. You need to get underneath the car to check. The nearside drain is located on the floor near where the fuel lines run front to back.

The nearside one (near the bonnet hinge) should be present. The offside one is redundant. Maybe someone has made the nearside one redundant too. Are you sure it's not just blocked solid with rotting leaf gunge?

TC

Thanks for this TC.....Ive only had the car for a month....I'm learning all the time.....No wonder the water wasnt running out of those pipes...dohhhhh.....

I think that the remaining rubber in the drain is covering the depth between the drain top and the bottom, so hopefully nothing seeping out in between...but if i get the chance to look underneath, i'll investigate it further..

Both the high ones have sealed rubber cups in the holes, would it do any harm to pull them out to investigate, I didnt want to risk tearing them, and finding they should be sealed and water leaks into say the bulkhead...I suppose, because of their height, they would only become effective, in a heavy rain storm...

 

[T-Cut]

Both the high ones have sealed rubber cups in the holes, would it do any harm to pull them out to investigate,

A plugged nearside upper drain must be a DIY modification. As noted earlier, Project Drive resulted in a plugged offside upper drain only. I think the nearside upper drain should be reinstated. This takes a big share of rainwater from the windscreen. There should be a drain tube as described earlier. This drains water onto the upper side of the wheel arch liner. It just dribbles off that onto the ground.

I didnt want to risk tearing them, and finding they should be sealed and water leaks into say the bulkhead...I suppose, because of their height, they would only become effective, in a heavy rain storm...

If the nearside upper drain is blanked off, then its share of water must go into the plenum. Providing the plenum floor drain (nearside) is kept clear, things will probably be OK. Water gets into the car interior via the pollen filter hatch. If the water level in the plenum reaches the level of lower hatch wall, it will overflow and wet the interior.

TC

 

[T-Cut]

Here's something I prepared earlier for newbies:

The Plenum
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 harbor 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, 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. A wet pollen filter will soon cause a bad smell from the air vents inside the car.
Flooding may also allow the ECU to become wet/submerged, leading to serious 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.

The plastic cross-head scrivets used to attach the water shield / plenum chamber are discontinued as OEM parts. However, Halfords sell the identical item HFX363 - Trim Panel Rivet at £2.30 per pack of 10

Windscreen scuttle panel Black Clip Part Number EYC101470PMA

Rimmer Parts Diagram: http://www.rimmerbros.co.uk/Item--i-GRID004308

This post has my quick find marker: #plen#

TC

 

[57vintage]

I agree on the N/S upper drain's necessity. Mine blocked and there was a helluva lot of water with nowhere to go.....

Unfortunately, after some over-enthusiastic rodding, I pushed the rubber tube through into The Void, where I hope it's very happy with Billie Piper. I made a ham-fisted DIY temporary fix with a cut-off flanged end of a washing machine filler hose and liberal volumes of shower sealant. That temporary job is still holding good 22 months later, so it's likely to be a permanent fixture.

I've started checking the plenum by removing the cover from the N/S and shining an LED inspection lamp in. As I understand it, the plenum floor is one-piece lateral to the car and all on one level. This means saving on the faff of taking both covers of on the N/S and losing the windscreen panel fasteners as they fly through space into the undertray, never to be seen again (I'm a Pela pump convert).

 

[T-Cut]

Rodding through the lower n/s drain is a lot easier and quicker if the water shield (under the outer grill panel) is fitted with a 25mm hole and grommet. The so-called 'spyhole' mod.

TC

 

[bassman]

Rodding through the lower n/s drain is a lot easier and quicker if the water shield (under the outer grill panel) is fitted with a 25mm hole and grommet. The so-called 'spyhole' mod.

TC

and it works a dream, thanks TC...I will have another look at my n/s high drain, and unmodify....

 

[anderfa]

I agree on the N/S upper drain's necessity. Mine blocked and there was a helluva lot of water with nowhere to go.....

Unfortunately, after some over-enthusiastic rodding, I pushed the rubber tube through into The Void, where I hope it's very happy with Billie Piper. I made a ham-fisted DIY temporary fix with a cut-off flanged end of a washing machine filler hose and liberal volumes of shower sealant. That temporary job is still holding good 22 months later, so it's likely to be a permanent fixture.

Hi ! Rover 75 2002mod
My rubber tube that you can see next to the hinge, on the side where the plenum drain is, was clogged. I prodded it with at 10mm bamboo stick. Coudn`t get it trough like on the other side of the car. Then suddely I pushed the rubbertube from its hole/flange, and it fell off into the car. Crap!!!
The clogged water went trough, ca down on the ground behind the wheel.

What to do, anyway to retrive the rubbertube ?

The rubbertube seemed totally closed, I could push the bamboo about 7-10cm, maybe it was blocket off ?

Going to check the plenum drain compartment for water tomorrow.

 

[T-Cut]

What to do, anyway to retrieve the rubber tube?

It's dropped onto the wheel arch liner. You can get it back by undoing the lower rear fasteners and getting your hand inside.

The rubber tube seemed totally closed, I could push the bamboo about 7-10cm, maybe it was blocked off?

It will be blocked solid with debris/rotted leaves, etc. You should clean it out before refitting it and ensure you check it every few weeks. It's an important rain water drain.

TC

 

[Skicon]

Rodding through the lower n/s drain is a lot easier and quicker if the water shield (under the outer grill panel) is fitted with a 25mm hole and grommet. The so-called 'spyhole' mod.

TC

http://forums.mg-rover.org/showthread.php?t=495570&highlight=plenums+reason