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Mike S.
Mike S., Mechanic
Category: Car
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Experience:  25+ years experience as an auto mechanic.
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Hi guys! I was requested to examine a car that has a leak

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Hi guys!

I was requested to examine a car that has a leak in the trunk coming from the top of the rear part of the vehicle. It is a Ford C-MAX Titanium. I think this might be a problem which can happen in any other manufacturer so I direct the question to all make experts.

The shop has already tried 2 times to solve the problem but it still leaks mainly in rainy days.

Can you suggest me which reasons can exist for that and also suggest some leak test techniques?

Thank you!

May I ask why this is being repaired by Ford under warranty?

Here is a warranty book for the 2010 Focus, which is about as close to a C Max as I can find, click here.

It's it rust it should be covered for 5 years.

page 11.

Your vehicle’s body sheet metal panels are covered for an extended
Corrosion Coverage Period, which lasts for five years, regardless of miles
driven. The extended warranty coverage only applies if a body sheet
metal panel becomes perforated due to corrosion during normal use due
to a manufacturing defect in factory-supplied materials or factory

At the least it should be covered under the bumper to bumper which is 3/36,000.

Customer: replied 3 years ago.



In fact there is a disagreement between Ford dealer and the owner.


My mission is only to obtain the confirmation that water is entering the trunk.


My first step will be to make a water leaking test. Is in that that a ask your help.


What is the best way to make that? I'll start using water with a bottle but they argue that only in rainy days it happens...


Can you help?



Do you know of anyone who is willing to lay in the trunk with a flashlight while you either use a bottle of water or garden hose?

Customer: replied 3 years ago.

I will do that.

Customer: replied 3 years ago.

Can you some specifics on the way I can simulate a rainy day; they say that even in a washing machine it is dificult to see water entering...


The garden hose.
On something that new i doubt if it's going to be rust. Perhaps, some glass was replaced and just didn't get sealed good enough. have you owned the vehicle since new? If so, was there any glass replaced? If you don't know, give me your vin number, I have access to carfax reports.
Customer: replied 3 years ago.



Can you please see this VIN?


I'll rate after this but I think you are a little offpoint because I don't care about warranty issues; I only have to check if there is water entering the vehicle as an independent expert.




I wasn't checking because of a warranty. I was just going to check if any glass has been installed and if so perhaps the glass didn't seal, like I said I was going to do, but Carfax says this vin number is XXXXX

Have you tried someone in the trunk and a garden hose?

Customer: replied 3 years ago.

OK I understand.


Can you check this? WF0EXXGC3EAL43040


I changed D by 3 because there was a site that reported a mistake in the VIN which is strange because I obtained it through a GTA Solution software (I bought 1 year license) and it allows to check via license plate nr.


I will do the test tomorrow morning; I'll let you know.


My idea is a 3 step test:


Step 1-bottle of water only in the rear side then enter the c-max via the front door and inspect the trunk with a flash light


Step 2 - if no water, i'll take it to a washing machine and will be inside


Step 3 - if no water leak I'll ask to spray the car with a jet wash manual washing machine...





WF0EXXGC3EAL43040 isn't a valid vin number either.

WF0EXXGCDEAL43040 was wrong also.

I believe there are 6 numbers that end a vin and in both cases you only have 5.

Why do you need software? Just read the vin under the windshield.

Customer: replied 3 years ago.

Yap; tomorrow I'll do that!


Thanks. I'll contact you after the test.




Customer: replied 3 years ago.



As promised, I did the test in 4 levels. First and second I used bottles of water because I had no garden hose, 3rd in the automatic washer machine and then in the 4th with the manual washing machine, "jet wash" during 15 min finished the test. Around 90 min after beginning water started to flow slowly in the inside plastics of the trunk door.


The VIN is WF0EXXGCDEAL43040. Note that this was registered here in Portugal and so may have a different logic.




Ok, so you found the leak. That's good.

That vin is invalid.

Let me see if I can find out why.


WF0=World Manufacturer Identifier-

E=Restraint/Brake Type-

XXG=Line, Series, Body Type-

C=Engine Type-

D=Check Digit-

E=Model Year-

A=Assembly Plant-

L43040=Production Sequence Number-

Did you actually look at the vin number and not refer to that software?

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