Help!

GENERAL

Cavity wax treatment

Q I recently made a decision to purchase Dinitrol Cavity Wax. It’s also sold in the UK in several variants. The item I purchased is the Dinitrol 3852, also known as Dinitrol ML. It is a brownish thick gooey substance that dries into a sticky film that adheres to the metal surface. I am appending the item for your perusal. This particular product is specifically recommended for older vehicles where rust might already be present. The argument seems to be that there is no need to treat the rust, and that this item can simply be sprayed over. I wanted to know from your expert opinion Steve, whether this claim is true or simply exaggerated. I haven’t seen any other player in the market offering a similar product like say 3M, Würth or Valvoline. They have cavity waxes to prevent rust, but none to treat it. Also, there appears to be no Tech-Sheet which mentions the composition – so I need your expert inputs.

Also, the Tech-Sheet mentions something called ‘wet in wet with bitumen UBC’. I wasn’t really sure what it was, but deduced that it might be spraying this Cavity Wax on the surface, followed by black rubberized underbody coating. Would you be able to provide me with some details please?

I wanted to know how long I can use my car before the next cavity waxing? Typically, how long do these things last?

I own a Fiat Linea (Grande Punto Sedan) that uses a 1368cc FIRE engine. The car is made in India and is nowhere near the British standard of manufacturing. There is no anti-perforation warranty unlike the 12-year warranty Fiat offers in the UK. My car was manufactured in June 2014 and purchased in Dec 2014 after lying six months in an open yard.

Kishore Thomas John Cochin, Kerala, India

A I would first say that my experience with the cavity wax products is based on its use in the UK, and as I would expect the climate in India to be slightly warmer this may have an effect on the use of the product.

Rust in cavities is of course very difficult to treat and as such a product that can prevent further corrosion in areas such as this is the ideal solution. The main basis of the product is that its viscosity allows it to fully cover and through capillary action to enter and seal off any small areas. Once sealed the absence of air and moisture will prevent any further corrosion from occurring.

Wet in wet with bitumen UBC does indicate that the bitumen underbody coating can be applied to the cavity wax, but I would not expect this to have any further benefit.

The cavity wax does harden slightly forming a skin and the ideal temperature for applying the wax is 15-25°C – this may be on a cooler day in your climate as a higher temperature will make the product thinner and may alter its ability to form a decent coating.

I think using the product now would encourage a longer rust-free period and once treated should be good for at least ten years.

The product does have good results and is effective. There are of course a few points to watch out for and this is to ensure that the product is not sprayed onto any area other than the body panel, especially where it may contaminate the brakes or impair the operation of a sensor.

The bottom line is yes, I would expect this product to preserve your Fiat and help protect it against underbody corrosion.

FORD TRANSIT

AdBlue system sensor

Q I have a 2017 Ford Transit 2.0 EcoBlue 170bhp Euro 6 with 21,000 miles. The AdBlue system has suddenly developed a fault with the tank level monitoring system. The tank does not have a contents level gauge, it just displays a warning on the information display when the fluid starts running low. The first warning shows ‘AdBlue Low Range 1490 miles’ and the AdBlue warning light comes on and stays on continuously – the info message disappears after a short time, then lights up again each time you start the engine displaying the diminishing miles.

At this point I would normally refill the tank to the brim with around 12 litres of fluid, but this time it only took around eight litres before overflowing from the filler, and the AdBlue light and mileage information stayed on and continued to diminish.

After three weeks the light and message suddenly went off, the mileage was down to 940 miles, then after four days with it off it suddenly reappeared again starting at the usual 1490 miles.

This indicates to me that the level sensor is faulty, and when it briefly came back to life it reset the BCM returning the info display back to normal, and now it’s had another glitch it’s again told the BCM the tank is low and the countdown process has started again, even though the tank is still full. Obviously if it continues to countdown without resetting, the time will come when I cannot restart the engine because it will think I’m out of AdBlue!

I have looked all over the tank for a level sensor of some sort, either float or pressure sensor but to no avail. I tried to buy a sensor from my local garage which is a Fiat dealer and a Ford service agent, but all they could come up with was a wiring loom for the tank, and I’ve looked online for info but found none. I found a breakers yard selling what they described as the level sensor, it’s a small 8-pin module that is fixed to the top of the tank. I thought at first it may have been an ultrasonic sensor, but when I took it off I found there was no aperture in the tank below it to sense the fluid. I bought the part as it was £30 and thought it was worth a try, but it made no difference!

I would be very grateful if you could tell me where the sensor is and if it can be replaced, I’m wondering if it is part of the pump/heater module as I cannot see anything else on the tank, but the ‘Spares Man’ tells me that part is £550 + VAT, and they have no idea about the AdBlue system – and wouldn’t even consider looking at the vehicle to establish what is wrong! So I don’t want to buy a new pump/heater unit on the off chance if the sensor isn’t even part of that assembly!

Andy Whitehead

A The 8-pin sensor HC345H297AA as you have found sits on the top of the AdBlue tank. This is an ultrasonic sensor which reads through the tank, and is in some ways like a radar sensor, using the top of the AdBlue to bounce the signal back. One of the problems that can occur if the AdBlue level is too high with no air gap is that the sensor cannot find the top of the AdBlue level as there is no gap between the tank and top of the