Had a good look under the bonnet at the weekend. From below I can see what I think are two of the core plugs and he there of them look to be red/wet.

I also had a look at the heater pipes and they also look to be free of coolant residue.

Car is now booked in at the local garage to be looked at properly. Luckily, they have an ex-LR tech that worked at LR when these were being sold new so he's nice and familiar with them :)

It was an expensive weekend, ended up buying the girlfriend a 1 year old Astra to replace her Corsa. It's giving frequent O2 sensor codes so I took a look and found engine oil in the connectors for both sensors. Turns out it's fairly common for an oil pressure sensor to fail and send oil out through various wiring looms to things like the ECU, O2 sensors and EGR electronics. Time for it to go!

Core plugs are only a couple of quid for the set, your get hammered on labour for a job that requires knocking something into a hole, I’d pull the manifold off and do them myself. Couple of hours to do both sides for peace of mind.

Sorry, I was typing on my phone and I seem to have suffered some kind of autocorrect issues that my proof reading failed to pick up on!

If meant to say that what I can see of the core plugs looks fine, no evidence of coolant from them.

It's going to the garage to be looked at so they can find the leak, not for them to fit core plugs.

So going to the local garage was a bust. They had it from 8:30 until 5:45 and reckon they can't find a leak.

What they did "find" was a weep from the radiator top hose that was pooling on top of the water pump.

I don't buy this as the water pump area was the first thing I checked as that was the gasket I replaced the last time I had a proper water leak. It was bone dry when I checked. He showed me the hose clip he tightened and it was wet in that area - but it doesn't look at all like it's been leaking for any time. There's no dried red coolant residue etc. Its also the most visible and obvious element of the cooling system. If my leak was there I'd have found it instantly!

So I'm no closer to finding the leak at the front of my engine :(

He does think the rear core plug is leaking but they need more time to confirm as he needs to remove the starter motor first to get better access to it.

On the plus side, they didn't charge me anything for having looked at it and hooked up their pressure testing kit.

Hmmmmm,, it’s so hard to diagnose unless it’s in front of you, there’s lots of places that won’t show when the cars running, as it seeps onto a nice hot engine, it gets evaporated, try and pressurise the system cold, ( don’t go crazy) then look for leaks. Rear core plugs unless the cars been run with no coolant for a long period is not really something I’d look at, there protected from elements,

Finally got round to picking up a UV torch and some dye.

Turns out the dye was unnecessary - the Halfords coolant I've been using is already fluorescent. This is both a good thing and a bad thing. It's good as I can already see coolant evidence but it's bad because it's fluorescent EVERYWHERE already!

The coolant is fluorescent red and shows nice and bright. I can see it running and dripping down the engines on both sides, front and back.

The dye I got is green so I put it in anyway to see if the different colour dye would make it easier to see the source against the existing backdrop of red.

It's noticeably worse at the front RH side, above the oil filter.

I don't think it's the core plugs as I understand those are under the exhaust manifolds. This leak is higher up and forward of the exhaust manifold. Shining the light all around the manifolds shows no coolant evidence.

On the LH side, it's higher up than the water pump and right over to the corner of the engine. I can't see any coolant evidence on the water pump or any of the pulleys etc.

On both sides it's higher than the oil filter/water pump but lower than the rocker cover gaskets - if I shine the UV light over the bunch of bananas and the rocker cover gaskets I can't see anything at all.

Is this starting to sound very much like a valley/lower intake manifold gasket?

I tried to take photos/videos of what I could see but it didn't really show up on camera. I guess phones have a way of filtering out that part of the light spectrum.

I found something else that surprised and slightly concerned me - when I shone the light at the top of the engine/intake manifold THE ENTIRE top surface of EVERYTHING was covered in an old faded green fluorescence. Kinda seems like at some point the coolant system had a proper meltdown and exploded all over the place. Hope what caused the flood of coolant was fixed properly by which ever previous owner had it at the time.

Luckily, there's no fluorescence on any of the interior....

If you've had a major aircon leak (assuming you have A/C) then that has a yellowey green dye in it for leak detection, it may be that your seeing over the top of the engine. Given the compressor on the v8 is up at the top as well its in the right place if that failed previously.

Bear in mind if someone who either believed the system was empty or was being careless just undid the hoses to the compressor this would have the same effect, equally the viscous fan or airflow through the engine bay could spread a gradual leak to get all over the place.

Have you checked around the throttle body heater, another favourite to fail and leak.

Throttle body heater has been bypassed and has no hoses attached anymore. There's also no evidence of a leak where the hose goes in to the top of the engine.

Sorry I guess I was a bit misleading when I said the coolant was "everywhere". It's everywhere in the bottom half of the engine, from about the oil filter down its over everything, I guess from it running down from the source and getting blown by the fans.

I’m wondering if there’s a pinhole in a hose somewhere, I’ve got the same, but mine is a light misting of atf across the bottom of the rads, I’ve been chasing this leak for a year, lol

At the rate I can see running down the engine on the RH side it must be more like a knitting needle hole than a pin hole!

I can actually see a flow of water.

The LH is a much slower leak, I can see drops appear every few seconds.

Now that I can see an actual flow I'm wondering about cancelling the appointment with the indy and going back to my local place. I can now point to am actual place so can see water from which guarantees there is an opening somewhere so their pressure tester won't hold pressure.

I’m steered towards your inlet manifold, it’s got to be high up to make it appear both sides, do you not know someone with a compressor, fill with water, shove air line with a rag wrapped round to pressurise,

Have you checked the O ring on the heater outlet from the manifold that I mentioned a couple of weeks ago? That's above the oil filter.

Your best bet might be to remove the fan and have another look - that way you know its not getting blown anywhere. Alternatively this sort of thing might help

https://www.ebay.co.uk/itm/New-15PCS-Radiator-Pressure-Tester-Kit-Cooling-System-Test-Detector-Set-tools/332521074244

Idea behind that is the same as Chris says above, put a bit of pressure in the system and see if you can detect any leaks that way.

Gilbertd wrote:

Have you checked the O ring on the heater outlet from the manifold that I mentioned a couple of weeks ago? That's above the oil filter.

I followed the line of where the pipe disappeared behind the alternator etc and pointed the UV torch in there - couldn't see anything.

no10chris wrote:

I’m steered towards your inlet manifold, it’s got to be high up to make it appear both sides, do you not know someone with a compressor, fill with water, shove air line with a rag wrapped round to pressurise,

I took it to my local garage (not an LR specialist) who had it for a whole day, pressure tested it and said it hold pressure fine. When I went to collect it they showed me a tiny wet patch from the radiator top hose, told me it was weeping from there and they tightened it up and it's fine. This is a lie as I know the top hose was NOT leaking when I took it in. I don't know anyone else with a pressure tester :(

BrianH wrote:

Your best bet might be to remove the fan and have another look - that way you know its not getting blown anywhere. Alternatively this sort of thing might help

https://www.ebay.co.uk/itm/New-15PCS-Radiator-Pressure-Tester-Kit-Cooling-System-Test-Detector-Set-tools/332521074244

Idea behind that is the same as Chris says above, put a bit of pressure in the system and see if you can detect any leaks that way.

The kit looks good but I'm not sure if it would help much. I can see where the water is running down from but the actual leak itself. If I pressurise the system wouldn't I then just see the flow I can already see but potentially a little bit faster?

I think what I'll need to do is get the pressure kit, remove things like the alternator, fan and AC pump and pressurise the system to see where it comes out.

BrianH wrote:

Your best bet might be to remove the fan and have another look - that way you know its not getting blown anywhere. Alternatively this sort of thing might help

https://www.ebay.co.uk/itm/New-15PCS-Radiator-Pressure-Tester-Kit-Cooling-System-Test-Detector-Set-tools/332521074244

Idea behind that is the same as Chris says above, put a bit of pressure in the system and see if you can detect any leaks that way.

Have you used this kit? It doesn't list Land Rover/Range Rover in the adapter list but does list BMW. Is the header tank on P38s a borrowed BMW item?

They do another kit, but it’s a lot dearer, with all the different caps, as Brian says, possibly remove some of the ancillaries and get a torch and mirror on a rod, you can then check all around, pity your not closer, I like a challenge.

Header tank is a BMW item, cap is the same as a similar vintage 5 series, more readily available and cheaper than one with an LR label too.

While my boss has been using the Ascot, it has been losing coolant so just been out to see if I could see where from. Ran the engine until it was hot but it isn't pressuring the cooling system (proving that it's a decent engine but has a coolant leak somewhere) so made up something to attach my tyre pump to. Lump of thick heater hose with tape wrapped around it to make it a tight fit into the header tank, with a smaller diameter bit of hose pushed inside that, EAS pipe joiner with tape wrapped around it pushed into that, short piece of EAS pipe then one of my EAS to Schrader valve adapters from the emergency get me home kit. That allowed me to use my tyre pump to pressurise the cooling system up to 25 psi. Easily enough to see it's leaking from at least 3 core plugs...... However, I very much doubt that is where your leak is from considering the age and history of your car. The Ascot is a '96 with 175k on the clock and a history of neglect so has almost certainly been run with plain water in the cooling system at some time in the past.

I'm now wondering if I can pick up a second tank cap, drill a hole in it and fit a tyre valve extension that we use on truck wheels.