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HVAC and water leak

01-05-2013, 03:15 AM
I have seen several problems and solutions to this water leaks in the HVAC system. None of the solutions seemed to solve my leak. Hopefully what I have found will help others. Pictures come later.

The water was not actually getting into the HVAC itself, but getting past the air inlet assembly from under the leaf screen directly into the firewall area. I will try a gasket maker that comes in rolls that I can press into place. there is no room for tools there.

Everywhere around the heater and AC module is dry. The foam on the inside firewall immediately under the air inlet assembly is soaked, yet the inside of the assembly is bone dry. I removed the entire to help diagnose the leak. A light rain was enough to fill the back foot well with an inch of water.

Hopefully more to follow.

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01-05-2013, 05:54 PM
Here are some images of the water leak source.

1. 47771

Water was found only in the circled locations. No water around heater/ac box.

2. 47770

Looking up from 1. above, I traced the soaked area up to air intake assembly which is sealed only with a foam gasket. Foam gaskets can get compressed with age and no longer seal.

3. 47769

With the leaf screen removed, you can see the air intake assembly. The foam gasket is exposed and will allow water to enter. I tested it by squirting water on the foam gasket area. The water streamed into the car. This will have to be sealed with some sort of gasket maker.

01-05-2013, 07:10 PM
What about some exterior silicon chalk. Stays somewhat flexible and can tolerate heat and cold.

01-05-2013, 08:02 PM
Caulk in the caulking guns would be impossible to apply in this area. If you look at the 3rd image, there is no room to get a caulking gun in there. I have a putty like gasket material that doesn't harden. It came in a roll so I can roll out an appropriate length, stretch it so that I have an appropriate thickness, then press it into the gap. I thought of using RTV sealant that comes in tubes, but that stuff would also be hard to work with in the small area. I've had the heat on the area for the better part of the afternoon to dry it out. I'll apply this stuff shortly then do a water test.

Then time for some new carpet!

01-05-2013, 08:14 PM
As an aside to this leak, imidazol97 (thanks!) pointed me to some other sources of leaks in the area, mainly under the hood hinges. This is not a leak I'd like to fix, because it looks as if I'd have to remove the hood. I don't like removing hoods and doors.

01-05-2013, 08:23 PM
At times like this, I get my daughter with small hands. Squirt some on her finger and she can reach back behind it. Had a similar leak but other car..

01-06-2013, 10:26 AM
As an aside to this leak, imidazol97 (thanks!) pointed me to some other sources of leaks in the area, mainly under the hood hinges. This is not a leak I'd like to fix, because it looks as if I'd have to remove the hood. I don't like removing hoods and doors.

In the past someone had pointed to a gooey, black material for sealing the watershield to the inside of the door metal due to leaks where the plastic cover had lost seal with the door metal. I believe it came in a roll held to a release paper much like the 3M caulk rope.

The 3M caulk is black and nonhardening that was mentioned. Check auto parts stores--this says it comes in 1 ft lengths, 60 to box...


I think that kind of material might seal well around the opening you are having a problem with.

01-06-2013, 04:04 PM
I used something very similar, only it was on a roll, not in sticks. It was given to me last year to fix a similar leak in my Grand Marquis.

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01-06-2013, 07:01 PM
I found a second leak around the air intake assembly. The water test around the wiper cowl area indicated the leak around the air intake was sealed so I was puzzled.

When I inspected the source from the inside again, the foam was dry from above the bottom seam of the intake air assembly, the part that switches from fresh air to recirculated air. I finally got my head right underneath and peaked up through the air intake assembly while holding the recirculation door open and could see water dripping from one of the wiper bolts. (Crazy design!)

I have not seen this leak documented yet, so maybe it's rare. However, if you're sealing up the air intake assembly leak, take a few minutes and seal the following up too.

1. 47775
Here's the wiper bolt, removed and cleaned. This is the one that was leaking. I used more of my sealant, warmed it up in my hands and stretched it into a log shape to wrap around the bolt just under the bolt head.

2. 47777
Here's a shot of the cowl just under the wiper stud showing how the water could leak through the threads of the bolt, and possibly past the wiper stud, straight down into the air intake assembly. The poor quality is a result of me using ISO 3200 so I could take the picture without flash, as flash would have left a lot of shadow, and burned out part of the picture at such a close range.

3. 47776
Wiper bolts now sealed. The excess sealant was removed from the bolts.

Now to go out and look for leaks. Here's hoping.

01-06-2013, 08:01 PM
Ugh. The first job I did putting the sealant around the opening of the air intake assembly wasn't good enough. I spent a good hour trying to press the gasket material in place and it still leaks.

I should have warmed the gasket material first. I'm going to get the hair drier in there later and try to press the stuff in better. Then I'll paint it with a body seam sealer or something.

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01-30-2013, 10:10 AM
I haven't worked on it for a couple of weeks, but I should add that I missed sealing the plastic hood to the metal bracket. Water will drain from the windshield onto the plastic hood, then leak between the plastic hood and bracket and drip straight into the air intake.

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02-02-2013, 07:38 PM
I sealed up the plastic cover to the metal bracket. After the sprinkler test, there was no water on top of the plastic cover/metal bracket which indicates there was no water leaking from that seal.

However, there is still water getting in. When I look under the metal bracket supporting the wiper pivot, the wiper mechanism immediately underneath the metal bracket is very damp. This means I did not seal up the bolts and pivot well enough as I had done earlier. I will dry it out then apply some liquid electricians tape.

03-12-2013, 08:08 AM
I am guessing that this is all realated to the leak problem that I am having with my Lesabre. My driver's area and rear driver side get a lot of water and I am just now starting my search. These photos and comments are so helpful. Thank you for posting.

06-18-2014, 08:53 PM

My LeSabre was still leaking through the fresh air HVAC intake. I found one more leak source (# 4 and 5 in photo)

To summarize, I used sealant around
1) the wiper pivot (may or may not have been leaking)
2) between plastic hood and metal wiper mount
3) body seam between wiper pivot mount and body (may or may not have been leaking)
4) lots of water flooding in here!
5) push pin holes- may or may not leak but worth it to seal up when installing the leaf screen.

Remember there were other leaks sealed not shown in this photo.

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07-05-2014, 12:54 PM
Ugh.I did a leak test with the sprinkler.The first 30 minutes were good, all was dry.Then after an hour and a half, it started pouring in. It was coming in between the air inlet boxand the firewall. I can only assume that my sealing of the air inlet box under the leaf screen was not good enough.

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10-09-2015, 06:41 AM
Did you ever manage to stop the leaking and how?
I am having the same problem with my Park Avenue and it looks very similar.
Water seems to be coming from the center of the car, just above the accelerator. I already tried sealant around the air intake and the horizontal seam towards the front of the car.
At the very least I thought the leaking would be less but it isnt.
I did not seal the bolts and wiper pivot, cause i looked and felt inside the air duct and it wasn't even moist unlike the rest of the rain tray.

08-06-2016, 10:44 AM
I've pretty much given up with it. I'm looking for a 2010-2011 Grand Marquis.
I've had a 1992 for 20 years with comparatively few problems. There was one water leak which was easy to fix. My Buicks had more problems in the 5 years I've had them.

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