Thread: I have a question

Sounds like the thermostat is not opening,if it's not the coolant will go through the bypass hose and the coolant in the block will start to boil and pressurize the header tank and split it.Change it and see how you go.It is the reason I don't like low coolant alarms,the engine will boil with both the temp gauge and alarm reading fine. Pat

So can we possibly assume that the thermostat got damaged due to the over heating caused by the aircon fans when idling.....

I know when ever you over heat on these engines you ALWAYS have to change the thermostat.

Idea: Put the expansion tank back in the 90 and drive it around.

In the meantime, I think the Disco is trying to tell you something.....take the head off, get it hardness/crack/warp tested, clean it up and put it back together.

The fact that your Disco has been hard to start for some time now would seem to indicate something was on the way out - and the overheating episode before this wouldn't have helped.

I gave my Disco a new head gasket and rings last year - and it's fine towing a big caravan around in hot weather ( You know that from our recovery effort up Mt Victoria). And my Disco is hitting 400,000 k.

youd want to hope its the thermostat, remove it and see what happens (assuming its not a td5 in which case its the head).

if you are very very lucky the head will be ok but i suspect not, try this.

with the thermostat out fill it up thentake the vehicle for a short run, just enough to get the temp gauge to move but not enough to get to normal operating temp.

Crack the bleeders and see whats going on, If you have froth add more coolant till all the froth is gone, if you have bubbles, sorry thats the head gasket..

This can also be done on the TD5 but its got a different and naturally more difficult approach. I like to do it with a 2l coke bottle with the bum cut out inverted into the filler of the expansion tank and sealed with bluetack but lifting the tank also works.

remove the cap and warm up the vehicle adding coolant as needed watch what comes out of the return line from the top of the radiator as it warms up

once its fully warmed up rev it past 2K rpm and observe what happens in the expansion tank (this is why I like the coke bottle whatever comes out of the tank floats up to the bottom (which is now at the highest point of the cooling system) of the coke bottle. again Froth is ok but bubbles are the head gasket.

to find out how bad it is recap the cooling system and take it for a drive as hard as your willing to and then let it sit, while its sitting pull the glow plugs out and disable the fuel system (pull the injector harness plug for a td5, or manually deactivate the fuel solenoid for a tdi) place some white cloth over the glow plug holes , hold it there with your nice cleaned fingers and wind it over on the starter. Any moisture is bad karma and usually means its done the head or the gasket.

Best of luck.

Originally Posted by langy

Idea: Put the expansion tank back in the 90 and drive it around.

90 is off the road still

In the meantime, I think the Disco is trying to tell you something.....take the head off, get it hardness/crack/warp tested, clean it up and put it back together.

The fact that your Disco has been hard to start for some time now would seem to indicate something was on the way out

-

and the overheating episode before this wouldn't have helped.

What over heating episode?? or you mean the one I'm talking about which happened in conjunction with the fans failing. other than that the car hasn't been over heated before. it got extremely hot on me one day after climbing the blue mountains but that was with a 90%blocked radiator and the car drove home absolutely fine that day..that was also well over a year ago

My disco is not hard to start!! starts before I have chance to finish turning the key think you have me mixed up with someone else..like I said the disco is driving fine

I gave my Disco a new head gasket and rings last year - and it's fine towing a big caravan around in hot weather ( You know that from our recovery effort up Mt Victoria). And my Disco is hitting 400,000 k.

...

Sorry Lou, I have a feeling the head gasket is possibly leaking, when your vehicle is driven up a hill, will the heater go cool?

JC

Originally Posted by justinc

Sorry Lou, I have a feeling the head gasket is possibly leaking, when your vehicle is driven up a hill, will the heater go cool?

JC

you mean if we have the heater on in the car does it go from hot to cold??

yep... if the system is properly bled up usually the first place that the bubbles collect is in the heater matrix and the circulation to the heater slows or stops. a sudden loss of heat from the heater is usually becuase your loosing or have lost coolant.

you can pressure test the head, all you need is a valve stem (one cut from a tube is usually the easiest), a cut down shanked bolt and a decent tyre pressure gauge and some spare 3/8th heater hose.

once you're satisifed that the cooling system is correctly bled, remove and blank the small return line to the expansion tank. to the expansion tank fit the spare 3/8th heater hose and then wedge the valve stem into the hose.

apply pressure to the system to the rated capability of the cap (should be 14psi-ish) with the tyre inflator and hold it in position to read the pressure over time.

Its a good idea to also have a small spray bottle of soapy water to leak test all your connections as they are usually the first place that leaks.

ok Its not as accurate as a designated testing device but it does let you get air pressure on and do a basic integrity test.