I've noticed a new damp patch appearing under the front of my car - it's a completely clear liquid that feels oily to touch and quickly goes tacky/sticky if I rub it between my fingers.

A very quick look under the front bumper shows it appears to be dripping from the bottom of the front diff - I don't know if it's coming from the diff itself or if it's dripping on to the diff from somewhere above. It seems fairly rapid leak - I was parked up at the side of the road for a couple of hours today and noticed a pool under the drip site about 15-20cm in diameter.

I just can't think what would be completely clear and oily - I'd expect any oil that was coming from the diff or inside something else with moving parts would be at least a little bit dirty. I've not put any fresh liquids in recently (besides a coolant top up - but that's red).

Engine, diff and transmission oils were done months ago but again, engine and transmission oil aren't clear. Not sure what colour the diff oil was though.

Any ideas what my mystery fluid could be?

Diff oil smells like cats pee, if that helps!
Put some clean newspaper under the drip. You can then identify the colour better.
Clear fluid that feels oily? Brake fluid? Check your lines...

Dunno what would be completely clear, but first thing for me would be thoroughly clean off any oil and muck around the diff plugs and the drive flange. Then you can soon confirm or rule the diff out.

Does the liquid smell? Gear oils horrible. Knocks me sick. Lol

EDIT. Orangebean beat me to it

I hadn't even considered brake fluid!

It had better not be a leaking brake line - it was MOT'd on 21/10/2017 and the only advisories were a tyre close to the limit and the O/S/R brake pipe slightly corroded. No mention of anything relating to the front brake lines.

I'll have to get a good look at it in the morning.

Front brake lines don't run anywhere near the diff so unlikely. I'd say diff oil, the modern stuff is almost clear, especially if you used the synthetic which doesn't smell like the mineral based stuff does. It hardly smells at all. It doesn't get dirty either but stays looking like it did when you put it in, there's no combustion or anything there to dirty it. Clean it off with a blast of brake cleaner so you're starting with a clean and dry diff. It'll be either the pinion oil seal or a porous section in the weld in the actual casing.

The oil I took out was properly filthy. It's was like a grey sludge, which is why I assumed the new oil would show some wear/dirt after a few months of use.

Glad to know there's no brake lines in that area.

I'm guessing a porous weld in the diff casing means it's new axle time?

There's 3 options if that is the problem, re-weld it (not easy as it's a pretty hefty lump and the oil inside it could catch fire), replace it (not cheap) or see where the porous section or crack in the weld is, drill it out, tap it and put a screw coated in Loctite in the tapped hole. The third method was used successfully on a Classic Range Rover that had the same problem on the rear axle.

Gilbertd wrote:

There's 3 options if that is the problem, re-weld it (not easy as it's a pretty hefty lump and the oil inside it could catch fire), replace it (not cheap) or see where the porous section or crack in the weld is, drill it out, tap it and put a screw coated in Loctite in the tapped hole. The third method was used successfully on a Classic Range Rover that had the same problem on the rear axle.

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I've seen the cracked case problem on quite a few cars (not P38s) over the years. Jacking on the drain plug and using a scaffold pole to tighten the tapered plug are a couple of my particular favourites!

Just my two cents for if it is the pinion seal.

you might wanna replace the drive flange too. May be worn allowing oil past. Worth the £25. Also, as its a bit of a chew job, dont buy a cheap seal. Get a genuine one.

Cleaned off the diff this morning and went out for a drive. Turns out it's a coolant leak dripping on to the diff from above. It just looked clear when I dipped my fingers in the puddle on the floor. Couldn't really see the leak on the diff when it was dirty and wet already.

Looks like I need to replace the rocker cover gaskets.

Does coolant leaking from the rocker covers mean something else is wrong deeper inside the engine? Valley gasket etc?

There isn't any coolant inside the rocker covers, so if you've got coolant leaking from there something has gone terribly wrong! A bit of condensation sometimes but that's all.
What you do have is a metal pipe that is sealed with an O ring feeding the heater matrix from the inlet manifold on drivers side. That could give the appearance of coming from rocker cover. You also have the throttle body heater fitting on inlet front top, temp sensor same place. top hose out from engine to rad which is fitted to a metal pipe again with an O ring seal.
Once again you're going to have to be more scientific with your leak hunting. I run UV dye (Ring RLD-2) in both my cars cooling systems permanently, which is a bit over the top, but it's really handy for locating weeps.
Your coolant shouldn't be clear either- should be a nice pink, gentle blue or sometimes green. If it's clear, it's not coolant, it's water and that's a bad thing to run unadulterated in your system

Sorry, I was a little unclear with my last message. The leak is red - it just looked clear on my fingers when I dipped them in the puddle under the car and wiped the drips on the diff. I couldn't see the colour of the leak or path it took along the diff when the diff was dirty.

Now that the diff is clean I can see clearly where the leak runs - it seems to be splashed all over the diff:

Here's the rocker cover:

And the pipes for what I assume is the throttle heater:

These ones have clearly been leaking at some point but look dry now. The one below appears to be leaking currently:

I doubt the throttle body heater plate will have magically healed itself. You can get a replacement for not a lot of cash or do what most of us have done and bypass it completely by running new hose from the head (where you have taken the other photo of a leak) to the coolant expansion bottle.

If you've got a steam cleaner, clean everything off. If you've not got one, go get one. For £20 you'll wonder how you ever survived without one. You can eat you're dinner off my shiny engine bay but more to the point, you can immediately see where there's a leak/cracked hose. Get all them pipes and stains sorted and you'll be able to see what you're doing.

Has your coolant level dropped?

Do you have any coolant hoses running along the bulkhead to an LPG reducer?

I don't have LPG on my car, patrol only. I do have a steam cleaner - I'll have a crack at it in the week. Wait for the little guy to nap and head outside with the baby monitor :P

Coolant level drops slowly over time and has done since I've owned the car.

I'll see about ordering a new hose and plate for the throttle body heater too. I've got a couple of other bits to order so I'll tag those on. Need some new tailgate struts, getting bored of getting a headache each time I open the boot.

Give it a blast with some degreaser first if you can then hit it with the steam.

A good work light to shine on/in suspicious areas is helpful as you'll be able to see any leaks glisten in the light and also If you have any of that blue kitchen roll, wrap a piece around any of your suspect pipes and run it at idle. You'll soon find your leak.

Hats off for no lpg. Petrol must be cheap round your way. Lol

It'd be worth sorting the coolant issue. I can't live with coolant leaks in case they mask something more sinister like a headgasket. But that's my brand of Paranoia :)

I don't think petrol is cheap anywhere! I used to commute 50+ miles per day in it and fuel in Peterborough was nearly always about 7ppl more expensive than in Leicester, where my girlfriend works :(

The leak will be found and fixed, don't worry about that. I thought I'd fixed it earlier in the year when i replaced the radiator and bleed hose. A previous owner had snapped the bit of the radiator that the bleed hose went on and "fixed" (bodged) it by jamming a barbed pipe connector in the newly enlarged hole and run a length of rubber hose to the header tank. What he had actually done is introduced a constant leak.

So which £20 steam cleaner has the official BPSM P38-Safe rating? Or should I just dig out the Earlex Steam Wallpaper Stripper thingy from the back of the attic and see what other bits are in the box?

Wouldn't have the nerve to point one anywhere near car bits, especially if it might hit electrics, without re-assurance from folks who have been there and done it.

Still chasing my teeny leak problem. Fix one, its good for a month then another appears. I figure its been run with magic sealer junk which is slowly wearing out after two coolant changes in my hands. Guess its time to join the "flushed my heater matrix group" although all seems to function adequately. Leak is more irritating than serious. Basically splash a bit of coolant in when I top up the screen wash.

When I did my throttle plate heater and hoses I found the hoses were sufficiently cracked in places for coolant to have oozed through the hose along the crack. Original hoses so after 16 / 17 odd years I guess they'd done their stint.

Clive

I'm not too concerned about the water. I've had mine up on the heated truck jet wash setup we have at work and gone to town on the entire underside a few times. Never had an issue.

I figured I've been wading with it up past the tops of the wheels and nothing bad happened - I can't get it much more wet than that!