Like many on this forum with a 4.4TDV8 I was chasing a slow coolant leak for a while. I finally got around to investigating it and found most of the hoses to be push fit type with O rings in the coolant circuit.

The hose/connectors seem to be servicible but most of the O rings were found to be marginal (flat) after 10 years of heat cycle.

I think it is time for this forum to put together a 4.4 TDV8 specific O ring service kit (coolant,Oil, etc) and proactively replace.

Note: the plastic bits for heater circuit and cooler were also brittle and were replaced. SOLD | Tuned MY 2011.5 Range Rover Autobiography 4.4 TDV8 Orkney Grey | e-diff | ACC

New Toy: Unimog U1550L/37
New : G350D

I had a thermostat housing leak, the housing was replaced but I only needed an `o` ring replaced,
It would appear easier to replace something than repair it.

Similar scenario for the induction pipe to the throttle body.

I also have a very slow leak but cannot see any sign of where it leaks from, despite my best efforts with a torch and standing in the engine bay to investigate. 2015 Range Rover Autobiography 4.4 SDV8

Gary, I cobbled together an old expansion bottle cap and an air line connector and put a gentle amount of air pressure in the bottle. I immediately saw a drip from my top hose to the thermostat housing. Can you try the same?

ffrr14 wrote:

I think it is time for this forum to put together a 4.4 TDV8 specific O ring service kit (coolant,Oil, etc)

I had the radiator degas hose go L405 but same engine - The old o-ring measured 8 x 2mm. A replacement 8x2 didn’t seem like a nice fit, but a 7x2 was really snug.

https://www.fullfatrr.com/forum/topic62151.html

Our thermostat housing also leaked, but only when at operating temperature and through a small crack in a manufacturing seam.

We’ve had 3 coolant leaks in the last 20k (cars only done 50k) which is crazy really. Sold - Bell a 2015 MY16 Loire Blue Autobiography 4.4 SDV8
Previously George a 2007 MY07 Java Black VSE 3.6 TDV8
Previously a 04 MY04 Defender 90

The L322 doesn't appear to have that fitting but L405 owners seem to have appreciated your information.

GraemeS wrote:

ffrr14 wrote:

I think it is time for this forum to put together a 4.4 TDV8 specific O ring service kit (coolant,Oil, etc)

I just replaced the o-ring in the thermostat housing end of the top radiator hose with what I expect is BS828 (I had several on hand), approx 46mm ID & 53mm OD. A low coolant level warning was occurring every 6 weeks after a top-up and coolant was dripping from this fitting. Not surprisingly the housing with the original seal slipped on and off the spigot very easily, but required a firm push or pull with the BS828 fitted.
The bottom radiator hose could have the same fitting but I didn't want to disturb the seal to check and it wouldn't be a quick a task to remove it.

Having measured the housing on the top I/C hose (90mm) and the throttle body spigot (81mm), I will obtain a BS620 to try.

garyRR wrote:

I also have a very slow leak but cannot see any sign of where it leaks from, despite my best efforts with a torch and standing in the engine bay to investigate.

The top radiator hose has the excuse of continual movement between the thermostat housing and the radiator for wearing its seal and due to the RR being my only form of transport I though best not to disturb joints that are currently sealing. Besides, I needed to get the grass cut before the rain starts again!

Got it.

Both the large thermostat(front) hose connectors are exacty the same in case you are wondering. I bought a second top hose and used the thermostat end only (this was unnecessary, should have just swapped the O ring)

Anyways I found dried coolant resedue past the oring up on close inspection. SOLD | Tuned MY 2011.5 Range Rover Autobiography 4.4 TDV8 Orkney Grey | e-diff | ACC

New Toy: Unimog U1550L/37
New : G350D

Thanks for the confirmation of the sizes. I'll be keeping a check on the sealing of the new o-ring over the next couple of days.
I can't recall why I had those o-rings but was fortunate to have them on hand.

The o-ring size that I fitted is 45mm x 3.5mm, not the previously quoted BS size. I'm trying to get hold of 2 in Viton 75 as nitrile's maximum temperature is a little low.

Oh I wish my (2012 4.4 TDV8) slow coolant leak would be fixed with cheap o-rings.
But it turned out to be the oil/coolant heat exchanger.
 2012 4.4TDV8
2000 Honda S2000