I have a 04 disco bought back in July,2012 and am having some bizarre coolant issues. I am a fairly new member and have not figured out how to post on the forum very well yet, hence the private message. You both seem to be the most knowledgable so I'm hoping you can help. Shortly after I bought it, I noticed coolant smell (no visible leaks), and started getting a misfire on #6 cylinder. Long story short, took it to dealership, told me I needed new engine, that I had slipped liner( this is what they told the former owner). But the engine runs beautifully(even with the 306 code)and is quiet. Took it for second opinion at an indie shop known for working on rovers. They ran a number of diagnostics and: they found no visible leaks externally. They did a pressure test and it held good pressure. Found no combustion gases in the coolant. No coolant in the oil. No smoking out of the tailpipe. Water pump shaft is tight and not leaking. Yet I have been losing coolant and am stumped. Starting a month ago it started overheating and I replaced the expansion tank cap. Solved the coolant loss for about a week. Then continued overheating and replaced the thermostat (have not had time to get the better thermostat and the ultragauge yet). Still overheating and purging the tank. I am at a loss and am wondering how much money should I sink into this or should I unload it? Any help would be greatly appreciated and thank you for your time

 

Did it over heat until the light came on?
How long did you run it when the light was on?
To me it sounds like you have a bad head gasket and possibly the pressure test was not done right. These engines were not built to handle even overheating one time but then again you have a 4.6 that suffers from the slipped sleeves so its hard to determine what you have going on and without having it in my possession i cant give you a 100% answer but our suggestions would be a good T-stat and a scanner with real time temps.
Green coolant.
New radiator or good flush.
Are you still running red/pink coolant?
The ultra gauge is a big help to have.
If you drove it 1 mile with the light on its more than likely time for a rebuild
Slipped sleeve usually makes a tick noise after it warms up.


Best advice is to stop driving it because if the heads are toast you are only going to f-up the block next if its not already f-ed up.

Very sorry for the news but with a bad block its a $1000 dollar truck.


If you have not replaced the front drive shaft its getting ready to fail soon to.
And after you get all that sorted you have about $200 worth of fluid to change out.

 

I am sorry that i had to type that message to you and push " post reply" that was about as bad as it gets. For your sake I hope somehow I am wrong

 

It's just weird, engine runs beautifully(aside from the recent overheating) and runs quiet. In response, I shut it off as soon as I saw the gauge start moving each time. I always watch it thanks to reading the posts! It had dexcool but I made a big rookie screw-up in that when I started losing coolant, I refilled it with green "add to any color coolant"coolant, so now it is all green - I'm sure I need a good flush. The weirdest thing is, the "service engine soon" light comes and at will and the exhaust always has been clear- no smoke. I appreciate the quick response and any other advice you can give- I'm putty in your hands guys! thanks

 

Here's something else, when I started getting the misfire on #6, I changed out the plug and it stopped coding. I inspected the old plug and it had no abnormal discoloration, no build-up or deposits and didn't look steam cleaned. I had talked to a mechanic friend of mine today and he said that it's possible that I could have a hairline crack in my hg, small enough that it wouldn't be dumping coolant into my cylinder but enough for the combustion to pressurized my coolant system. Have you ever come across a situation like that?

 

How often & how much coolant are you using/ leaking?

 

If you have just a standard coolant leak to the ground - put in Barr's leaks.
One bottle - and see if it stops.
That would mean - you don't have an HG problem.

If you put in Barr's leaks and you are still losing coolant - then you may have an HG problem.

A slipped liner makes a noise at idle usually - when the engine has run for a matter of 1/2 hour or so.

Usually a pretty loud rapping.
You don't have that.

 

Definitely sounds like a head gasket leak. I know because I just went through this problem and replaced the gaskets and everything is fine now.

 

I actually just tried Barr's. It has stopped the overheating, but still using coolant ( much less though - just topping off every couple days - probably 1/2 pint). While this stuff seems to have worked as a temporary fix, I hate to think of everything it's probably gumming up. Thanks for the responses!

 

Well I am glad you added some Barr's.

Sounds like what i went through.
I had white smoke out the tail pipe.
And a misfire on #1.

Put in two cans of Barr's leaks.

Misfire went away.
Steam out the back greatly reduced.

But ---
Still huge pressure in the bottle and in the hoses.

If I took off the coolant cap - after sitting an hour - the bubbles would come up and the coolant level would lower as I recall.

Replacing head gaskets SOLVED IT ALL.

And I have never looked back and regretted it.

Replacing them is a chore and can't be hurried up if you are taking on this issue on your own.