overheating 300tdi defender

[johnodef]

hi guys
i have 1995 defender 300tdi which is running hot:
new thermosat and radiater and installed vdo gauge and matching sender runs at 100 deg on 30 deg day
no leaks holds pressure and does not boil, heater works ok
therostat housing hot
when run at idle doesnt get to temp bottom hose is hotter than top and radiator cool to touch, circulation problem?
have bled air out of water alarm on top thermo housing
, what next?
thanks

[110 Pete]

hi guys
i have 1995 defender 300tdi which is running hot:
changed thermosat and radiater and installed vdo gauge and matching sender runs at 100 deg on 30 deg day, what next?
thanks

Hey Johno,

Have you checked the pipes, earth conection, temp sender into the block is in properly and all the wires are wired correctly. Apart from that beats me

Goodluck

Pete

[jboot51]

viscous coupling for the fan ?
I had an aftermarket one that wasn't locking up soon enough.
Made the temperature rise.
A quick manipulation of the spring on the front and has been fine for several years.
If your not getting the loud fan roaring noise, then the viscous is most likely failing.

[460cixy]

If the top hose is cold and bottom is hot seems a bit odd the hot water leaves the thermostat housing and the cool water comes out the bottom maybe wrong thermostat or crook water pump seems odd tho that it does not cook at idle.

[jimr1]

hi,run engine till hot ,turn off , if you can turn fan blades by hand its you viscuse coupling not working ,when hot it should be locked on and shoud be tight therefore pulling air through your radiator.it sounds like its not spining .

[slug_burner]

radiator? has it ever been cleaned? have you always run the correct coolant?

if you don't get the roar of the fan when it comes on then it is suspect!

As pointed out below, the radiator is new. Hmmm!

[steane]

my 300tdi Defender did exactly the same thing. Turns out the radiator was largely blocked. Had the tanks removed and the core rodded and now perfect.

[2stroke]

I'd have said radiator as well but johnodef mentions a new radiator in the first post. Possibly the aircon condenser could be blocked? I've done 2 viscous fan hubs over the last 10 years, both still turn by hand when hot, both are genuine Rover. Did each as a (expensive) precaution when the problem was a blocked radiator.

[johnodef]

thanks guys
new radiator and air con condenser removed, will take it for a run and check the viscous coupling
do water pumps actually fail to pump?
could there be an air lock?
i have bled air out of the alarm in the thermo housing.

[wrinklearthur]

thanks guys ------ new radiator ----

With the new radiator everything should be good, --- But !! --- if the cooling system hasn't been flushed properly at the change over to the new radiator, rubbish that is still loose in the galley's can still plug the tubes in the top of the core, the flow then bypasses most of the core, going direct to the outlet via the huge bleed hole in that baffle plate half way down in the tank, ( I am currently experimenting with a radiator that has the tropical mod done, where that hole has been reduced down to 3 mm ).

The symptoms of just this problem, is that the engine heats slowly on a constant pull and is slow to lose it's heat when stopping to cool it down. This cooling time can be sped up by spraying water around the radiator tanks and the top of the engine, I have used one of those pressurised 5 Litre garden spray filled with water to do this and it was APITA to do each time it got hot, but it worked enough to get me home.

and air con condenser removed, will take it for a run and check the viscous coupling

Borrow a good viscous coupling and give that a try first.

do water pumps actually fail to pump?

Yes, I have seen a impeller totally rusted out and on another, the impeller was spinning on the water pump shaft.
I had a batch of bad bearings in some of the cheap pumps ( $ 30 each approx plus freight ), I suggest that you buy a ' QH ' brand or better to save yourself some grief.
When you change the water pump do the 'P' gasket as well, as when the tension is released off the bolts the housing can spring a fraction breaking the seal on that gasket.

could there be an air lock?

Try this, the bleed pipe from the top of the thermostat housing can block at the plastic venturi, pull the hose off the thermostat and blow through the air bleed pipe while squeezing the pipe shut that goes into the top of the radiator first and then squeeze the pipe shut that goes to the expansion tank, you should be able to blow easily through both pipes. If it is blocked a 3 mm drill bit can be used clean out the ports of the venturi.

have bled air out of the alarm in the thermo housing.

Interesting, I installed my alarm sensor into the top of the radiator tank as per the instructions, it seems to work well there and the wiring is better protected running down and along in front of the radiator.

Pull your thermostat, pop it into some hot water on the stove, it should open steady and be fully open just before the water boils ( 88°).
Just as important, check that when the thermostat is cool that the valve is fully closed and there is no light coming past it's sealing face.

I use in a 300TDi, a 50 /50 mix of green coolant changed once every two years.
.