P38 Overheating - Best way forward please?

OK so I've been here before, about 18 months ago, only last time it was as a result of a knackered water pump. It's a 1998 DT.

This time it started as overheating on motorway on Saturday and I pinned it down to water loss from two pin hole leaks from the heater top hose. Patch job on hose and top up saw the journey safely finished, then Monday managed to source a spare and replace it, and all was well with the world for another 150 miles, before it overheated again very suddenly. Popping the bonnet revealed a split rad (again no huge surprise, it happened last time), so it was a ride home from Mr RAC for us and car.

After getting a replacement rad I've started stripping the hoses off the get old one out and having undone g-box cooler hoses was promptly showered in MTF (yeah I know that's normal), but what caught me by surprise was it was mixed with large quantities of water! Now I realise that this would strongly indicate that the cooler joints inside the rad are likely to have failed (They're only soldered, cause I had the last one apart to have a look).

Clearly just replacing rad is not going to be enough, but what else do you reckon/suggest? No mentions of boxes of matches please Obviously g-box is going to need draining/flushing/refilling, but what else, and has anyone else had this???

Update.... just dismantled old rad and no obvious sign of internal cooler element failure, although there are signs of slight twisting from doing-up/undoing the cooler hoses, which might mean there is a small leak there. The other interesting points are there was a hardened lump of some sort of sealant, shaped like about an inch worth of toothpaste squeezed from a tube?? and also about a small handful of sandy substance, colour of casting sand but courser. There's no sign of this blocking the core as I can see daylight through it with ease, but what might it be?? The whole cooling system was stripped and flushed only 18 months ago, and drained and refilled only 6 months ago??

Nightmare, hope you get it sorted.My rad on my diesel split last thursday and overheated.

What coolant have you got in there? If it's a silicate based coolant rather than the orange extended life oat coolant, then the sandy substance is probably silicate that has settled out of the coolant.Nothing too serious and to be expected with silicate coolants as long as its not a huge amount.

Can't think how else you'd get coolant into trans oil other than a leaking trans oil cooler in the bottom of the rad. Was it an OE rad?

Kungfu0210 said:

Nightmare, hope you get it sorted.My rad on my diesel split last thursday and overheated.

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My first one went 3 weeks after getting car, when water pump impeller became a pile of plastic bits. I carefully reconstructed it to make sure there was none left floating round the system, and got a replacement with metal blades, so that shouldn't be a problem now. At the time my research found split rads are common in hotter climates, and the Aussies recommend changing them every 90-100k.

Kungfu0210 said:

What coolant have you got in there? If it's a silicate based coolant rather than the orange extended life oat coolant, then the sandy substance is probably silicate that has settled out of the coolant.Nothing too serious and to be expected with silicate coolants as long as its not a huge amount.

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Don't know what was used in it before, but I used Halfrauds Advanced, which is OAT based.

Kungfu0210 said:

Can't think how else you'd get coolant into trans oil other than a leaking trans oil cooler in the bottom of the rad. Was it an OE rad?

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Neah, it was ****part:doh:, Nuff said! Although at that price I can go through several of them without spending as much as a LR one

Had a further thought..... does this logic make sense to anyone else?

G-box cooler is built into water rad, therefore it's reasonable to assume g-box runs significantly hotter than rad, otherwise there'd be no cooling effect. If already hot pressurised coolant water and even hotter g-box fluid mixed, via suspected leak, then you'd get high pressure, superheated steam, hence blown rad.

QED???? The only bit of this theory that doesn't track is that excess pressure should have vented via g-box breather.

After big battle with the gearbox drain plug (clearly hadn't been moved since car left factory), I drained box and ended up with 1/2 and 1/2 coolant and MTF! No sign of emulsified fluid, so hopefully draining and refilling will be enough. Fluid was good and clear too, no signs of burning or contamination (apart from the coolant:doh. Any signs of gear probs and I'll drain and refill it again. Ended up too dark to sensibly see to start up and test, so have left that for the morning.
Given that gearbox hasn't been touched in twelve years does this look like a safe amount of metal on the magnetic plug? Probably looks worse in pic than it is, as it's all very fine almost soapy particles, nothing gritty or spikey, as it might at first appear.

As long as there are no metal splinters on the drain plug, it's ok. Is it a manual transmission or auto? Auto's don't like coolant in them, if it's a manual then it is unlikely to have done any damage.

spadgr said:

As long as there are no metal splinters on the drain plug, it's ok. Is it a manual transmission or auto? Auto's don't like coolant in them, if it's a manual then it is unlikely to have done any damage.

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It's manual, auto wouldn't suffer same problem with it's seperate cooler element.