It was almost this time last year that I replaced the radiator, viscous fan & coupling, thermostat, rad expansion tank cap and various hoses (because the old ones were fat).

Things have been great, coolant never dropped, no overheating, I've been towing my boat around no dramas. Only thing I've maybe noticed but not sure if its just in my head is that the old gal feels a bit down on power. I just felt like when I first got the car a few years ago it towed better than it does now, but that's besides the point of this post.

Unfortunately, the other day I noticed my expansion tank was half empty And I could see coolant looked to be leaking out the radiator header tank around where it seals to the core, on the non-inlet side. I couldn't see if it had dripped down the core or not, just look as though it had seeped out.
Taking a look under the car, I could see the bottom of the radiator tank had been dripping coolant. Again, on the non-outlet side (the side furthest from the thermostat). I couldn't see evidence of coolant running down to that section, it seemed to be leaking from the radiator itself.

Something else I spotted that may be troubling, is my RMS leak seems to have a nice coolant-coloured-green tinge to it when inspecting with a UV light. I'm not sure if that's simply what happens to the colour of oil under a UV light, but when I inspected oil on the dipstick I didn't see any green.


Does this smell like a munted headgasket? Cracked head? That might explain why the old hoses were fat and perhaps the extra pressure has caused the rad to leak?

Happy days

What engine? Diesel? What's RMS?

Sorry, deets are in my signature. 2001 P38 4.0L petrol. RMS = rear main seal.

Thanks. I misread 'header tank' as expansion tank. All makes sense now.
Does the top hose go rock hard or can you still squeeze it?
Unlikely to have a cracked head, more likely to be a gasket or cracked block. Do you get bubbles in the coolant?
Old rubber hoses do tend to lose shape over time

Surely you found the problem - leaking radiator ?? Replace that, and then search for other leaks if the coolant still drops.

If it hasn't overheated, but you're still worried, do the usual stuff, i.e. check the spark plugs for steam cleaning, pressure test with engine warm but not running, and get an "exhaust in coolant" tester.

I wouldn't say the top hose goes rock hard, it's firm, but I can still squeeze it a bit. Will look into the bubbles in coolant thing

This is the 2nd radiator in 3 years or so, figured something else might be at play. I certainly hope the solution is just to buy a nice alloy rad and its not gasket related

can squeeze a bit.. is that a popeye squeeze while frowning very hard? it should be an easy squeeze, not just a millimetre or 2

I had two replacement radiators fail on my DSE in three years don't think that they are all up to the job. First one just split but the second one blew the whole top plastic section off in spectacular fashion. My local garage then got another new one and this worked fine for the rest of the time I owned it.
The other thing that failed was the pipe where the top hose joined the engine it just weeped a bit and then crumbled away crumbled away.