Thread: Does anyone let their vehicle cool down before a water crossing?

Yeah I do it. Should minimise water into diffs. Also good practice to check a crossing before charging in, I think.

The iseal is to have the air in the housings at the same temperature as the water - rarely will you get that (most places water temperature is below air temperature), but the closer to it the less pressure reduction when the housing is chilled by the water. And any decrease in the pressure difference means the airflow through the remote breather is less, and hence the pressure drop is less. After all, they are usually quite long and none too large diameter!

Originally Posted by martnH

I always stop and let the driveline and engine cool down

As said before the hot air inside gearbox transfer box and diffs if rapidly cool down, will create a vacuum to suck water in

If you have a defender, it is particularly important because those stupid rubber cap on drive flange will act as diff breather

Don't you also screw the wading plugs in in a Defender?

Originally Posted by weeds

Has anybody actually checked temps after the pre-determined cooling time??

I have always thought that while your driveline is still above the temp of the water it could suck water in....., therefore thinking it would take longer than 5-10min or the couple of minutes it takes to check depth.

To date I’ve never had water contamination after water crossing. Maybe it’s the breathers sucking all the cool air in as it’s they have the least amount of resistance for air to travel compared to oil seals.

Yes agree with this.

Vehicle components are at their hottest after the vehicle has just stopped,particularly after a long run.

It will take a lot longer than 10 to 15 minutes for the drive train to cool down,unless ambient temperatures are particularly low,such as south of 20 degrees.

Sure,it is better to let things cool down before going through deep water,but it will take a lot longer than 10 to 15 minutes for this to be effective.

Checking all breathers are fitted correctly and not blocked is also very important.

Iv'e found most extended breathers are not breathers at all, they usually have enough oil vapour that has condensed overtime to form a meniscus of oil in the tube. Normal driving is fine, the meniscus moves up & down as the diff heats / cools but a sudden dip into cold water the oil wont move through that thin tube so fast and water gets sucked in via seals etc. Probably no better than the old fashioned breather valve on the diff tube. Good idea to camp the other side of the river & crack your diff / gearbox plugs the next morning the oil wont have emulsified & you can drain off the water sitting at the bottom of the oil.

Originally Posted by goingbush

Iv'e found most extended breathers are not breathers at all, they usually have enough oil vapour that has condensed overtime to form a meniscus of oil in the tube. Normal driving is fine, the meniscus moves up & down as the diff heats / cools but a sudden dip into cold water the oil wont move through that thin tube so fast and water gets sucked in via seals etc. Probably no better than the old fashioned breather valve on the diff tube. Good idea to camp the other side of the river & crack your diff / gearbox plugs the next morning the oil wont have emulsified & you can drain off the water sitting at the bottom of the oil.

OMG! I’ll never drive a puddle again

I've heard that the procedure is:
Pull up, look at river. Reverse down river bank until tires touch the water then drive out. This leaves a set of tracks coming out of the river on your side. Pull over. Have a cup of tea and let everything cool down. In this time someone will almost certainly drive up on the other side. They'll see your tracks and you and assume you've driven through. They'll drive through. Watch them and learn if it's doable or not.

(Confession: I've never done a river crossing)

Originally Posted by scarry

Yes agree with this.

Vehicle components are at their hottest after the vehicle has just stopped,particularly after a long run.

It will take a lot longer than 10 to 15 minutes for the drive train to cool down,unless ambient temperatures are particularly low,such as south of 20 degrees.

Sure,it is better to let things cool down before going through deep water,but it will take a lot longer than 10 to 15 minutes for this to be effective.

Checking all breathers are fitted correctly and not blocked is also very important.

Its a question of judgement obviously. If you've been doing 110kmhr up the highway for a couple of hours, more than 10-15 mins will ideally be required. Time for a cuppa and a break anyway. If you've been pootling along at 60 on a dirt track, 10-15 would probably be enough.
Any cool down time is always better than none.