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[flymofred]

I thought I would drain/backflush the radiator to see if I could stop the alarming rise of the temp gauge when slogging up hills. I have the undertray off and I can see a drain screw, but surely the 25mm odd hose above it isn't the bottom hose. Also what is the sender unit directly above this 25mm hose. I have discovered the sender below the top hose switches on the electric water pump. So is this lower one the fan relay switch. Can the rad. be backflushed using the drain outlet it is conveniently similar into size to a garden hose.

Thanks

martinH

[hoofing it]

Has the viscous fan been removed.
what temp.is it going up to. mine goes to around 92.
the 25mm hoses that are attached to electric pump are for keeping the cab warm until all the heat from the engine has gone.
the only other 2 options are water pump or the thermostat

[flymofred]

The viscous is still on. Thermostat changed about 2 years ago prior to that it never reached  min. temp and got colder and colder off load in the winter, after changing it warmed up right quick and stayed steadily at just above 90.It still runs at just over 90. However with what seem little hard work it  now rises rapidly towards 100 and if you then run the car gently it takes much longer to come back down. So going up long gradient with a caravan on the back is heart in the mouth stuff. Where then does the bottom hose join the rad. blowed if I can see it, or can I ignore it and back-flush through the drain outlet.

Thanks
martinH

[Welung666]

Change the waterpump and thermostat, less that £50 for both and easy enough to do

My money is on the impeller seperating from the shaft of the waterpump.

[hoofing it]

I'd agree with welung666 change stat and pump he should know

[TheBoy]

On the TD, there is a drain on the rad (the red one, near hose) and on block (aft of turbo).

Check the waterpump, but methinks it hasn't been having a good enough oil servicing schedule.  How often do you do the oil?

[flymofred]

eerrr I think it might a year don't know how many miles that is. I guess I'm up for online kicking. What is the mileage interval, and will a change help or is too late? :-/

[Welung666]

eerrr I think it might a year don't know how many miles that is. I guess I'm up for online kicking. What is the mileage interval, and will a change help or is too late? :-/

Mine is changed every 3,500 miles MAX! The oil starts to breakdown and seep through seals, do you have a lot of oil drips on the top radiator hose behind the passenger headlight?

[TheBoy]

eerrr I think it might a year don't know how many miles that is. I guess I'm up for online kicking. What is the mileage interval, and will a change help or is too late? :-/

BMW state 4500 miles MAXIMUM.  To be honest, thats too long.  I thought 3k was about the limit my old TD would do before ruining its oil.


That BMW engine, like all BMW diesels of that type, are prone to oilways and piston cooling jets clogging up with 'black sludge' if the oil service interval is ignored.

You *may* find that a good, strong oil flush helps, as this may clean out the oil jets in the piston coolers, which will help keep temperature more under control.

[flymofred]

thanks for that I'll give it a go. I feel I may have racked at least 9k miles (ooops) a lot of those with a van on the back. and yes ever since I,ve had the car oil mysteriously leaks onto the top hose is there a seal I can change?

martinH

[Welung666]

thanks for that I'll give it a go. I feel I may have racked at least 9k miles (ooops) a lot of those with a van on the back. and yes ever since I,ve had the car oil mysteriously leaks onto the top hose is there a seal I can change?

martinH

No but all of the induction chambers will need a good flush out (inlet plenum and 'turbo diesel' stamped strip along with the pipework).

[Seth]

Exactly the same problems that my previous 2.5TD had
Fitted new 'stat, rad and water pump, plus strong engine oil and cooling system flush to no avail.
Came to same conclusion as TheBoy.

Engine oil/filter-change, plus 'Turbo Diesel' manifold cleaned every 2500 miles.

[Evo]

I had the same problem on my 2.5TD. My advice would be to use an infra red thermometer to check that you've really got a problem & to assess the performance of the radiator.

My non expert two pennyworth is that modern oils will last 10k miles (but change at 5k to be safe) & back flushing a rad is ineffective.

My temperature surging was very much reduced by a new rad but measurements showed the temperature guage was reading too high anyway. My temperature now doesn't go above 95 but I reckon its really about 85.

[osealy]

Had same problem.
Changed pump & stat = no difference
Flushed rad                 =no difference
Fitted new rad             = cured!
Viscous present but not working.

[TheBoy]

My non expert two pennyworth is that modern oils will last 10k miles (but change at 5k to be safe) & back flushing a rad is ineffective.

Even fully synths don't last that long it would appear.


But in the case of diesels, the oil has an additional function to carry away particulates from the combustion process - this is part of the reason that diesels turn their oil black almost straight away.