L322 4.4v8 m62 coolant leak

ok so i find myself with a coolant leak again, the car has always used a bit of coolant but recently it has got worse, i've checked the usual suspects, water pump, thermostat, radiator, valley pan (with an endoscope) & rear of engine and there are no obvious leaks. i did have a couple of puddles of water one at the front of the engine and one at the rear, but these were clean water so best guess is that was from the air conditioning. however i am getting some strange issues with the hevac system. if i have the car set to a low temp so 18degrees both centre vents blow cold (set on max cold) but if i move the wheel to max hot, passenger side blows hot air and drivers side dosent. but it works ok if i raise the temperature control to say 22c on hot it's hot on cold it's cold on both vents. i'm kind of thinking it could be heater matrix or the valve assembly on the inner wing, however i don't know how that would cause a leak.

Air con drains are either side of the gearbox.

Expansion tanks are known to crack.

UV dye and torch might help , valley pan would not be easy to detect a small leak, alternator housing is water cooled.
Coolant manifold at rear of engine and the two tubes feeding it are fairly well hidden even with an endoscope.
You could also try a coolant system pressure test and keep your fingers crossed one of your spark plugs isn’t getting steam cleaned

someone else mentioned head gasket before, but no evidence of it, car runs fine no white smoke and no gunk in the oil, i think the rear puddle is definately aircon,. however it's always used a bit of water and i noticed in the service history suspected valley pan leak but no evidence of it being fixed if it was, however after doing 40,000 miles in 5 years i wouls have thought it would have got worse before now. took it for a run tonight and it stayed at 90-95c temp (i have 85 degree stat fitted). guess i know what i'm doing on thursday!

There is a small drain hole at the back of the engine where the valley pan is, I think it’s under the PCV valve , I’m away so I can’t send you the fot of it but will try later. If it’s a small leak then I guess it would evaporate being making itself known

yes that is possible, heater matrix was my other thought but got no coolant smell in the car, and the carpets are dry

Matrix leak womt leak into cabin, it will leak out of the aircon drains......ask me how I know.....twice.

hopefully it's a nice day tomorrow to give it a service and i can try and 'hunt' the leak

I think these are drain holes..

cool cheers fella, i can focus in that area and round those dreded pipes , strangely i'd rather it be valley pan than heater matrix lol

so it's getting wierd, car is booked in for a pressure test on tuesday, it seems i have 2 leaks at the front of the engine, one seems to be fairly central running down the front of the engine block, so best guess is water pump or thermostat gasket, (my guess is thermostat gasket) as there is no play in the water pump and it hasn't got noisy bearings but i could be wrong. it does seem to have a 2nd leak down the right hand side of the engine, which seems to be running off the alternator housing but it is possible that is down to the leak in the middle dripping onto one of the belts and getting splashed over onto the housing (one pulley and belt looked slightly wet). the leak at the back dripped either side of the gearbox after the car had been running for to warm it up to change the oil, however at that point heater was on with aircon on. however it's only using very little water again so the front leak could be the only one. i do however also think i have the heater valve gone faulty (stuck open) after i had done the oil change and the car had cooled down quite a bit i started it back up to warm it up and make sure it was ok, and i decided to check the heater hoses as if the return is hot it could indicate a leaking matrix (allowing hot water into the matrix as it leaks) however both the return pipe and the the right hand inlet pipe were at engine temperature.

You have the two aluminium pipes that plug into the back of your water pump and are only sealed by an o ring and also a gasket where the pump fits to the block. Your alternator has a big o ring keeping the water jacket sealed also. My top hose that runs to the pump from the right hand top of the rad when looking at the car blew apart a year ago, there is no jubilee clip just a steel band - not the reggae type

there is also a weep hole in the front timing cover behind the water pump, which means the whole cover has to come off to fix it, luckilly it's not that, it's also possible it could be from th lower temp thermostat kit i have fitted at the mo, going to investigate a bit more today and see if anything is a bit more visable, definately a strange one though as it dosen't seem to leak all the time.

right so went out this morning and low & behold the piece of cardboard i left under the front end had water on it, great seems the car leaks more so when it's cold so i looked from above to see the pulleys wet right under the thermostat, so i pulled it apart had a look at the tubes into the water pump both were dry,so i bit the bullet so to speak and called my local indie and decided to go go for a new thermostat (i previously had one of the lower temp stat kits on that uses the sandwhich plates) so after much swearing and cursing i got the old kit off, popped of to my indie to pick up the new stat. it turned out the new stat was a britpart unit but my indie says he fits them with no issues so i decided to fit it. firstly i noticed i had activation cooling map error on the ecu (because of the previous stat kit) so i cleared it then filled up with water and fired the car up. keeping an eye on the engine temp with my diagnostics, i touched the top hose and it was starting to let hot water through to the rad, checked the temp 72 degress, i thought strange and it seems the stat is fully open by 79/80 degrees. i checked the activation cooling map error again and it was back, tried to clear it 5 or 6 times and it just came straight back. so my conclusion is either britpart have modified the standard stat to open at a lower temp or mine is faulty, either way just wait to see if i get anymore drips of water now the cars stood & cooling.

in fact scrub that it seems i have a fault with the cooling map wire car goes to 105 with it disconnected, but it stays activated permanantly when plugged in, but thats a job for another day!

The connector that goes to the stat can get corroded and either short or burn out, what wire is the cooling map wire?

I’ve been out and checked it with my multimeter and it appears the connector on the thermostat is shorted direct to earth on the negative side so it looks like I need to get in contact with my local indie and get a replacement stat, otherwise it’s going to be stuck open until the coil burns out.

you can get a lower temp stat that bolts straight in without the need for the mod, i have a new one that cost me about £100 but you can get them a lot cheaper now

yes i did have one on, but mine was the kit with sandwich plates and cutting the old stat out of the body great mod, but mine had become problematic 99% sure it's where my leak was, so i opted for a standard stat as i need to use the car the weekend, but ended up with a faulty one, still it'll get me through the weekend.

so it went in today to be pressure tested, they pressurised the system and the damn thing didn't leak from anywhere and no drop in pressure. until they fired it up, looks like the water pump is also on it's way out so not as bad as i expected, no leaks from the back so that's all good news to. in my panic though looking at heater matrix' as i didn't find like the LR price, it turns out you can buy a hella matrix for around £86 which is bmw x5 fitment (which is the same unit fitted to the RR)