poorly disco overheats at high revs(sometimes)

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cawl

New Member

Posts

86

Location

UK Manchester

• Jul 14, 2009

• #1

hello everybody(anybody) i have a 96 300tdi disco all was well for ages untill recently i t overheated on the motorway i changed the thermostat as i was assured by a mechanic that that was all was wrong,at the same time i changed the header tank coz i had a new 1 handy,since then it has a mind of its own.It seems my heating hardly ever works only at at high revs like on the motorway 70mph, it will sometimes start heating up into the red so i have to slow up to 50ish and it will cool down to temp or the heating will just kick in,then its fine until you come off the motorway the heating cools down.At low revs 2000ish theres no heating at all but the engine temp is fine, it only overheats at high revs when the heating isn`t working which is most of the time,help please its doing my head in!!

 

sp33der

New Member

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372

Location

A Geordie in sunny Spain divvent ye knaa

• Jul 14, 2009

• #2

well, if you're sure thre head gasket's ok it sounds like an airlock somewhere or a blockage - maybe in the heater matrix - did you flush the system and make sure it was properly filled, with coolant circulating and the thermostat open? test the thermostat too, even new 'uns can be faulty

cheers
Rich

 

C

cawl

New Member

Posts

86

Location

UK Manchester

• Jul 14, 2009

• #3

i`m certain the heads ok it was done 12 months ago but an airlock sounds likely as i was told that off some1 already ,thank`s mate

 

andyb66

Well-Known Member

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1,795

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Middle of Salisbury Plain, Wiltshire

• Jul 14, 2009

• #4

Check and see if the heater is giving you hot air.

There is a hose at the back of the head that goes to the header matrix and it is about as high up as the top hose, so it maybe that there is an air lock there.

Also worth taking a quick peek thru the radiator with a torch and checking that you haven't lost a lot of the fins. It maybe that working the engine that hard is just too much for a tired radiator.

 

C

cawl

New Member

Posts

86

Location

UK Manchester

• Jul 14, 2009

• #5

thanx mate,had a look rad looks almost new,like i say sometimes the heater works, only at high revs, if it doesn`t then engine overheats. at low speed it doesn`t heat up temp gauge is in the middle but no heating ever

 

C

cawl

New Member

Posts

86

Location

UK Manchester

• Jul 14, 2009

• #6

what`s the easiest way to flush the cooling system and heater matrix out so i can be rid of these headf##k air lock`s?

 

C

cawl

New Member

Posts

86

Location

UK Manchester

• Jul 14, 2009

• #7

so i`ve been looking under the hood and i notice that most of the water hose`s are hot but the one for the heater matrix aren`t so maybe that`s my trouble? would this cause my engine to over heat? is taking the thermostat out tempory gonna harm the engine?

 

andyb66

Well-Known Member

Posts

1,795

Location

Middle of Salisbury Plain, Wiltshire

• Jul 14, 2009

• #8

You need to cure the air lock.

One way, is to carefully loosen the hose clip on the pipe that leads to the heater matrix with the engine running and the air should be released from the system.

There is also a filler plug on the thermostat housing. You can remove this and check that the head is properly full of water.

Remember to top up with an anti-freeze mix not just plain water.

 

C

cawl

New Member

Posts

86

Location

UK Manchester

• Jul 14, 2009

• #9

ta mate, had a look under hood seems that the bung on the therm housing has been replaced at sometime with a rusty rounded nut(nice) would the heater matrix air lock make my engine overheat?also if i take the therm out as a tempory fix will this harm the engine?