why do cdt/cdti not suffer from water in diesel?

[vincentfishing]

Just read a post about moisture and hydraulic fluid and recalled how all diesel machines on building sites had water traps and water drain offs on bottom of filter, indeed my old toyota estima had a water warning light on dash,when lit i would drain off water from tap on bottom of filter.on site we were taught that the more air in machine fuel tanks the more water/condensation would get in system so we always kept tanks filled. so back to my point why no drain off/ or water problems in our diesel ????

[klarzy]

Originally Posted by vincentfishing

Just read a post about moisture and hydraulic fluid and recalled how all diesel machines on building sites had water traps and water drain offs on bottom of filter, indeed my old toyota estima had a water warning light on dash,when lit i would drain off water from tap on bottom of filter.on site we were taught that the more air in machine fuel tanks the more water/condensation would get in system so we always kept tanks filled. so back to my point why no drain off/ or water problems in our diesel ????

Because we have a return fuel cooling radiator which cools the fuel before it goes back into the tank...

It sits just behind the rear OS wheel.

[vincentfishing]

always wondered what that was

[marinabrian]

And plastic fuel tanks, and rubber delivery hoses......

You been for an MOT yet Vincent ?

Brian

[HarryM1BYT]

I did a full service yesterday, pouring the clean fuel from the diesel filter back into the tank rather than waste it. At the very bottom of what came out of the filter, were a few drops of water.

I don't quite get Klarzy's bit about the fuel cooler, but agree warmed fuel returned to the tank will help prevent condensation forming, as will the sealed breather system and use of plastic for fuel components. .

[vincentfishing]

yes brian, it failed on rusty brake hose and one balljoint, not bad for a car that was last mot'd in 2012,and prior to test gave it a blast down the local dual carriageway to clear the cobwebs was very impressed with the 160 upgrade,thank you .

[James.uk]

>>>gave it a blast down the local dual carriageway to clear the cobwebs<<<

A good blast is a good idea at anytime with a diesel engine, mine gets one every time I use it..
...

[T-Cut]

Originally Posted by vincentfishing

Just read a post about moisture and hydraulic fluid and recalled how all diesel machines on building sites had water traps - - - so back to my point why no drain off/ or water problems in our diesel ?

Water condensation needs two things, moist air in the tank and low internal temperatures. The amount of air getting into fuel tanks varies between petrol tanks and diesel tanks. The high vapour pressure of petrol foms a 'protective blanket' inside, so there's very little air getting in. The high vapour pressure is why petrol systems have the carbon canister. Diesel oil has a relatively low vapour pressure, so more moisture gets inside.

The plastic construction of the fuel tanks reduces heat conduction, so less heat is lost in cold weather compared to a metal tank. Diesel fuel in the tank also tends to be warmer than petrol due to the backflow. If left long enough without use, water will eventually be formed. This also applies to very old petrol in tanks. Eventually, the high vapour pressure components evaporate leaving a damp more oily liquid that will refuse to ignite properly

Moisture absorbtion by hydraulic fluids is a separate issue, caused by the chemical affinity of polyglycol type fluids for water in the atmosphere.

TC

[vincentfishing]

just serviced my rexton 2.7 diesel(mercedes engine) prior to selling now i have another 75, and hey presto water sensor on bottom of fuel filter, funny how 2006 merc engine still has water problems ,but old rovers /bmw dont !!!