Rust now appearing in ...

[philharve]

Hi All

I was refilling my windscreen washer reservoir when my eye was caught by a small patch of flakey rust that was appearing around one of the drain/vent holes in the underskin of the bonnet. Though not serious, I decided the spray Waxoyl around and inside the hole, between the inner and outer skins of the bonnet. No doubt that will inhibit the spread of the corrosion.

Then I got to thinking that finding rust in the engine compartment area is unusual (IMO) because the hot, oily environment tends to drive out moisture and coat the exposed, painted metal surfaces with a fine, greasy layer that helps keeps moisture at bay and inhibits the corrosion process. Finding rust on the bonnet's inner skin therefore came as a bit of a surprise to me. I wonder how common it is in Mercedes vehicles? I have seen it in other makes, particularly where it spreads and eventually eats through the bonnet's outer skin and creates unsightly rust bubbles under the paintwork.

I like Waxoyl because it's widely available and it's relatively inexpensive. But I have used Dinitrol's range of products on my previous car with great success and I thought I would like to use them again on the Merc'. I have purchased a couple of Dinitrol's spray products from Frost Restoration along with several 60cm spray hoses that should enable me to reach into every cavity of the bonnet. On the next fine day I will give my bonnet's cavities a good rustproofing treat.

But I am still wondering why rust should break out in the underskin of the bonnet? Could a small leak in a windscreen washer hose initiate the corrosion process because where the rust has formed, around a hole near the leading edge of the bonnet, is not a water trap area. Has any other member experienced corrosion in or around the engine department including the underside of the bonnet?

REGARDS

Phil

 

[television]

These day oil leaks and fumes get less and less, so having that protection film is getting less and less.

There are quite a few rusty engine compartments out there and I have been shocked by some of the pictures.

Bonnets are double skinned, and the chance of much paint on the inside is small.

I like Waxoil and Dinotrol though I always thought that the Dinatrol was a little too thin to work with.
How did you find it Phil

 

[philharve]

Waxoyl -v- Dinitrol

Hi Malcolm

I like using Dinitrol because IT IS THIN and therefore runny and it gradually creeps along seams and into inaccessible box areas and cavities through capillary action and gravity. I have used Waxoyl and a hot-air blower with much the same result. I'm not sure how penetrative Waxoyl alone would be, it's a bit too waxy? Some members recommend thinning Waxoyl with engine oil to a consistency similar to that of Dinitrol. I have never tried thinning Waxoyl myself.

I have often wondered whether the cavity enclosed by double-skinned body parts are painted or protected to inhibit corrosion. Your comments suggests that such cavities may have very little or no protection. I can appreciate that paint won't reach these areas but doesn't Mercedes inject rust inhibitor into these areas before the vehicle leaves the factory? Your remarks suggest they probably do not?

Is there any reason why I shouldn't try to inject/spray the bonnet cavity with rust inhibitor because a little over a year ago I had a first class, expensive (Phil paid), back-to-bare-metal, paint job performed on the bonnet. I'd hate to see rust bubbles appearing from beneath and ruin the fine paint finish? If rust did break through the outer skin, would this be a warranty job, i.e. a new bonnet?

I had the bonnet resprayed for two reasons. Firstly, because corrosion was appearing around the windscreen washer jets and along the trailing edges of the bonnet and, secondly, whilst the leading edge of the bonnet had only a few stone chips, the nose would look better with a fresh coat of paint. And this is what happened; I now have a spotless, mirror-finish paint job. I'd like to keep it that way. Having rust form on the underside of the bonnet is threat which I'd like to squash early.

I can understand that there is probably less oil vapour in the modern engine compartment and therefore less protection afforded by it. However, a hot engine and cold air probably gives rise to a fair amount of condensation and if there is no protective, oily layer then corrosion would seem an inevitable consequence. Taking action as soon as rust is detected would seem the only course of action.

REGARDS

Phil

 

[television]

I agree Phil and do it everywhere that you can .

Re Waxoil I heat it up to 25c and use an old spray gun and spray plant to do it it atomizes completely and gets into the odd corners.

I used Dinatrol in Sweden and I do remember a lecture where the creeping action was shown,, they are both good.

Put as much as you can, everywhere that you can and you will not go wrong

 

[philharve]

Thinners - what are the alternatives?

Hi Malcolm

I have never used thinners with waxy rust inhibitors, such as Waxoyl, but I have heard the use of engine oil is quite widespread. However, I have heard of paraffin, petrol and methylated spirit being used. Seems to me this concoction has all the ingredients to recreate the 'Big Bang'. Is there a less explosive thinning option that is safe to use, excluding heat?

REGARDS

Phil

 

[ernieh]

Do Not Use Petrol...........

Hi Malcolm

I have never used thinners with waxy rust inhibitors, such as Waxoyl, but I have heard the use of engine oil is quite widespread. However, I have heard of paraffin, petrol and methylated spirit being used. Seems to me this concoction has all the ingredients to recreate the 'Big Bang'. Is there a less explosive thinning option that is safe to use, excluding heat?

REGARDS

Phil

On NO account should petrol or methylated spirits be used to thin waxy rust inhibitors! When used as solvents, they flash off far too quickly and in the absence of ventilation will give rise to pockets of flammable gas, which, as Phil says is more than likely to go BANG.

In a previous life, I have used White Spirit, which eventually evaporates and leaves a nice waxy deposit. I have also used heat by immersing the reservoir in a bucket of hot water.

The entire process is made much easier by doing these jobs during the summer - we used to get some warm summer days 30 years ago!

Ernie