Rover 45 / MG ZS Water Ingress Troubleshooting Guide

Rover 45 / MG ZS Water Ingress Troubleshooting Guide

The Rover 45 and MG ZS are based on a ‘tried and tested’ Honda design - while it’s a great chassis with many positive aspects, one flaw is the amount of possible water ingress points that exist (particularly on the Mk2 variants, where the seam sealing seems a little more careless). 

In this guide we’ll run through the common ingress points, how to fix them and how to dry out your interior if it’s been damp for a while. 

First of all, you’ll need to identify where the leak is entering the car - in this guide we’ll cover the most common points from front to back. 

We see most reports of ingress focused around the front passenger footwell and a roughly 50/50 split between water on top of the carpet and water underneath. 

The difference may seem trivial, but it’s actually crucial in determining the source of the water - leaks under the carpet are usually from a seam failure, whereas leaks on top most commonly enter the cabin through the heater blower inlet. 

Leak resulting from front passenger bulkhead seam failure

Seam sealer failure is becoming more common as the cars age; it dries out and cracks allowing water through the points at which it has split.
If you have water under the front passenger carpet, you’ll need to pull the carpet back to inspect the various seams and follow traces of mud left behind to find the source of the leak. 

Remove the kick trims along the bottom of the door shut, release the carpet from the two clips under this trim, take off the small plastic trim in the left-hand corner of the footwell and you should then be able to lift the carpet. 

At this point I’d also recommend removing the glovebox - this gives a lot more room for inspection and remedial work. 

When you pull the carpet back you’ll probably be surprised how much water you find!
I used a large bath towel in the footwell to soak up the water sitting on the floor; I then used several more towels stuffed between the carpet and floor over the next few days to help dry the foam carpet backing out. Check the condition of the floor carefully and treat any corrosion if applicable. 

To find the source of the leak, pull the sound insulation back from the bulkhead (where your passenger’s feet would rest if outstretched) - if it’s the usual common failure point behind the dash you’ll see a line of mud / dirt (along with water if it’s recently rained) running down the seam on the far left of the passenger footwell where it meets the bulkhead (see photograph below, the usual route is indicated with a red line). 

To fix this you’ll need to remove the heater blower motor housing for access; this can be a little fiddly but with some time and patience can be done with only basic tools. 

First, remove the glovebox if you haven’t already done so - then remove the pollen filter from its housing. 

Next you’ll need to remove the various bolts and screws holding the blower motor housing in place - including the blower motor itself. The motor will drop out easily once the three bolts holding it in are removed.
Undo the three small gold-coloured screws around the pollen filter slot (one to the left, two to the right) - this allows the join in the pollen filter housing to open up slightly to aid removal of the blower motor housing. 

You will also need to unclip the various connectors and wires running across the housing - move the cables out of the way to avoid straining or damaging them. 

Finally you can remove three bolts holding in a dashboard support bracket to give a little more room - one of these is under the square cover on the end of the dash (visible with the door open, near the airbag child seat warning sticker), one is just inside the glovebox aperture (bottom left) and the third is to the left of the blower motor housing, quite far up but visible with a torch. Removing these will allow the end of the bracket in close proximity to the blower motor housing to be moved left slightly, giving more room. 

Once all of the bolts and screws are removed, you’ll be able to wiggle the blower motor housing free (if it won’t move easily, check again for any bolts or screws you may have missed) and you can remove it. Usually this is most easily done by pulling it downwards, but it does take some effort and ‘fiddling’ to release it. 

The seam is as pictured above - it runs horizontally behind the blower motor (against the inner wing) and any ingress will run down the inner wing to bulkhead seam before soaking into the carpet backing. 

 

Before repairing the seam, you’ll need to make sure it’s clean and dry otherwise the new sealer will likely fail shortly after the repair is complete. 

We recommend our 1KG Seam Sealer - it’s a product we’ve sold for a very long time and has proven to be excellent in service. You can find this on the DMGRS website. 

Use a microfibre cloth to remove any loose mud and debris, then use a wire brush or similar to clean the seam sealer back to a ‘new’ surface free from any signs of contamination. The surrounding area should also be clean and free from rust, dirt or other materials. 

Finally, make sure the gap between the two panels is completely dry before moving onto the next step. If in doubt use cotton buds or similar to check there’s no water present. 

Apply the seam sealer with a stiff brush, making sure that a good amount makes it into the void behind the cracked seam to ensure the joint is completely water-tight. Leave it to dry for the time specified on the packaging, then add another coat. 

Once cured, you can refit the blower motor housing - as the famous saying goes, refitting is the reverse of removal! Be sure to clear any leaves etc caught in the blower motor or pollen filter slot. 

We recommend changing the pollen filter while you’re performing this job - it’s very easy to do while the glovebox is removed. We have them available on the DMGRS website under part number JKR100020. 

 

Leaks on the driver's side

The driver's side bulkhead is prone to similar leaks as the passenger side - the seams can fail, and rubber grommets etc may not be fitted correctly (sometimes from the factory). 
Common areas for ingress include the bonnet release cable grommet, the same seams as detailed in the passenger side guide above and a few seams around the bulkhead area (accessed from the engine bay). 

A customer made us aware of a couple of leak locations he'd found (thank you, Philip!) - we've detailed his findings below. 

After having a new windscreen fitted to try and cure the issue, it was found that water was still making its way into the cabin - this led to exploration of the engine bay for possible areas of ingress. 
The seam in the driver's side corner of the engine way was found to be cracked, and also not to be fully sealed as the pictures below show. 

Water from the windscreen runs into this area if it misses the scuttle, meaning it has easy access to inside the vehicle (especially if scuttle drains are blocked or the seals are poor etc). 

Another area found to be lacking in sealant was a seam further down in the engine bay where the steering column passes through the bulkhead to the steering rack - you can see the spot welds, but the sealant is missing. 
The top and other side of this protrusion were sealed properly. 

The final possible ingress location was found in the driver's side wheel arch - where the dark blob of underseal is pictured, a small hole was found due to the underseal cracking with age. 

Leak resulting from ingress via heater blower inlet

If you have water on top of your carpet or the carpet itself is damp, you’ll likely have water entering via the heater blower inlet. 

This is located within the plenum / scuttle between the engine bay and cabin - the inlet is protected by a simple flap of metal which can let water enter the car in certain situations. 

To fix this leak, you will need our Scuttle Panel Cover Seal Kit - DWG100040PMP - the seals of the scuttle cover will need replacement, so you will need this kit on hand when removing the cover to adjust the inlet. This kit is available from our website. 

The kit also includes detailed instructions regarding how to adjust the inlet flap to prevent water entering your car - this involves bending the flap back a few degrees to avoid water falling from the channel above and re-sealing the seam around it to prevent ingress in the event of a blocked drain. 

Leaks from vehicle roof or boot hinges

There’s a few leak points around the roof of the 45 / ZS - we’ll run through the most common areas. 

Starting at the front of the vehicle, the windscreen seal itself can be a source of leaks - both from failed bonding on an older windscreen to a badly fitted replacement. 

It’s important to remember that the black windscreen trims you can see outside the vehicle aren’t seals - they’re only there to prevent mud and other debris filling the channels around the windscreen. 

If you have water entering the vehicle at the top of the windscreen, check for any rust bubbling in this area - even if it seems quite minor it could be much worse underneath the trim. Rust bubbling can lift the windscreen from the car body or allow water through hairline cracks in the metal caused by corrosion. 

One ‘quick fix’ for this is a solution such as Captain Tolley’s Creeping Crack Cure - it’s a very thin liquid that follows small cracks then sets as a flexible sealant. We’ve used this on similar leaks with great success. 

Long-term the windscreen will need to be removed, the rust treated (often requiring the welding in of new metal), the area repainted followed by the windscreen being refitted once all work is complete.

The rubber seal around the base of the aerial is another source of leaks - these can degrade with age and sunlight exposure. Usually this shows as water making its way into the interior light assembly - if you have water here, this is likely the cause. 

Removal and replacement is quite simple; it’s accessed by removing the interior light. Make sure you clean the area of the roof the seal sits against to prevent future leaks. 

Running from front to back you’ll see there are two channels covered by rubber strips - there’s a seam running the length of these that can leak, along with a known weak spot where the front of these meets the windscreen surround (corrosion develops here, but luckily access isn’t too bad so it can be re-sealed without removing the windscreen). 

Remove the rubber covers by sliding them towards the back of the car - if you can’t do this, carefully lever up the centre of the cover and it should release from the locating pins at each end. You may need to ‘wiggle’ it a little to dislodge years of mud and dirt in the channel which can hold the strip quite firmly in place. 

Once removed, clean the channels thoroughly and inspect the seam within the channel wall - it should have a good, clean finish with no breaks or corrosion present. 

You’ll also be able to inspect the area mentioned above where this channel meets the windscreen - make sure it’s free of any mud etc, and check for corrosion at this point carefully. If in doubt, apply a small amount of sealant over the suspect area. 

Finally, the rear windscreen (and boot hinges on the hatchback models) is the last area to check. You’ll usually know if you have a leak here by a soggy headlining - on hatchback models this is usually due to the seam near the hinges splitting or the sealer itself cracking with age.
Inspect both carefully and re-seal any areas you feel may be the cause of issues. 

If the rear windscreen is leaking, it can run down into the boot - this is harder to trace but you can use Captain Tolley’s Creeping Crack Cure to make sure the seal is good.
Carefully apply it around any suspect areas - if a lot of the solution disappears, there’s a good chance you’ve found your leak. The way I usually use this product is to keep ‘topping up’ any leaks I do find with Captain Tolleys until they’re filled, leaving a few hours between applications. 

Leaks within the boot area 

There’s a lot of areas around the boot which can leak on the 45 / ZS - along with the hinges and rear windscreen above there are also: 

• Rear light seals. After a downpour of rain (or application of hose pipe) check the area under the lights for water run off. Also feel the bottom of the light unit itself for any collected water between the plastic housing and the car body. 
• Clips holding the bumper in place. Use a hose pipe to apply water to the area around each clip - it may take a minute or two for the leak to appear. Apply lots of sealant around any affected clips. 
• Rear boot vents. Same as above - spray water around the area then re-seal if needed. 
• Fuel fillter neck area rusting through. This is one I’ve seen twice so far - on Mk2 models the corrosion protection around the fuel filler neck area is poor, meaning it can rot through to the boot itself. Look carefully down the left-hand side (when looking into the boot) gap between the outer shell and inner metal structure - you’ll see the bulge where the filler neck passes to meet the area behind the fuel filler flap. I had to use a USB endoscope to get a good look here, but this showed a split seam and some corrosion.
  I used a spray sealant to re-seal both, and will apply a good amount of Bilt Hamber Dynax UB to the area behind the filler neck when I remove it later this year. 

Leaks caused by blocked door drains or faulty door vapour seals 

These aren’t very common as the doors on the 45 / ZS are well-designed with plenty of drainage - but well worth covering in any case as we have seen sporadic reports of issues here over the years. 

The door drains allow water running down the window and into the door casing to escape - these can fill with mud or leaves over the years leading to a buildup of water. Once it reaches a certain height it’ll then be able to spill over into the cabin. 

Remove the door card and you’ll see the vapour seal first - carefully peel this back from the door casing taking care not to damage it. 

The drains run along the bottom of the door casing and are quite small - hoover out any larger debris and then use a cloth to make sure they’re all as clean as possible. 

The vapour seals can also cause leaks if not fitted correctly - make sure they’re firmly stuck to the door casing with no gaps in the sealant. If they’re torn or otherwise damaged we’d recommend a temporary repair with something like duct tape, however in the long-term replacement is usually best. 

Summary

I hope this guide has been helpful - we’ve worked on a lot of 45s and ZSs over the years and this just about covers all of the usual water ingress points. We’ll update it regularly with any new information passed to us - if you find you have a leak not covered by this guide feel free to email details to us (sales@dmgrs.co.uk) as it could well help out another owner in future.