Thermostat or Head gasket?

Hi all,

Had an issue on the way home from work the other morning. The heater in my Disco 1 started blowing out cold air when set at hot? Got home and checked coolant level, all looked ok. Drove to work the following night and the same thing happenned. It did start to warm up after a while but then started to turn cold again. When I checked the cooland level after my journey home there was evidence of it having come out of the bottle and also looked like ther were signs of oil in the coolant. The top rad hose also felt like it was under pressure.

The temp gauge ran normal for the duration of the trip with no sign of overheating...

So what do you think, head gasket, thermostat or something more sinister. Oh BTW the car has just completed 100k miles....

you cant check real coolant level without removing bugs 1 on rad other on thermostat housing fill till all overflow including expansion tank it will find its own level in the tank by blowing excess out of cap ,you can check thermostat by feeling top hose it will stay cold till thermostat opens check rad is hot all over core surface ,if all all right replace head gasket they only cost a tenner and a mornings work

hi, my disco had same symtoms, turned out it was the head gasket, it didn't show many signs, only main sign was the the header tank was pressurising badley! the garage said the cooling system was filling with exhaust gas, hense the pressure! which is why the water had came out of header tank cap! the cap itself is a pressure valve if you take it off and look underneath! hope this helps and sorry to be the bearer of possible bad news!

Ok, so I've come to terms with the fact the head gasket needs replacing. Is this something I should try and do myself or pay out £300 for someone to do it for me? I've bought the Haynes Manual, got the tools and TBH it doesn't look like too much of a ball ache. Concerns I have are around stuck manifold bolts/nuts shearing off etc. Anyone on here had similar problems when doing this sort of work. Also, is it advisable to get the head skimmed or not. Bearing in mind the engine has not overheated at any point with no visible signs of leakage from the H/G. Would you advise changing anything else while I'm at it? (tappets etc)

All advise much appreciated...

its the kind of job thaat can be simple and straight forward but can quickly turn in to being a cnut, have you ever timed an engine before? and its always worth skimming the head and then you know its true

I did mine a couple of months ago. Its a doddle to do. I didn't have any problems with snapping bolts off either. You can leave the manifolds on, but to be honest it does make the head alot heavier. Things to watch out for thou. if the bolts do come out, when you rebuild it again, do not over tigthen the manifold bolts as its a ali head and you will chew the treads up. Also to make things easier remove the rocker arm shaft, that way its alot better to take the push rods out. Only other thing i can think of is that the rear head bolts, won't come all the way out beacause they hit the bulk head.
things to be removed:
top and bottom rad hoses
top and bottom intercooler hoses
injector supply pipe
injector bleed off pipe
engine breather pipe from rocker box
exhaust down pipe
turbo and exhaust manifold
inlet manifold if you wish
rocker box cover
head bolts
air filter to turbo pipe

leg oot the bed said:

its the kind of job thaat can be simple and straight forward but can quickly turn in to being a cnut, have you ever timed an engine before? and its always worth skimming the head and then you know its true

Click to expand...

Not for many years although i thought the timing wouldn't be affected as it's an OHV engine...

sorry just woke up aye you are right, your only problems as yousay then are seized bolts but you cant predict them unfortunately if it was anything like my disco the oil leaks wouldnt let anything seize lol