300TDi overheated

On the motorway last week when I saw temp gauge off the scale - 2-3 mins earlier it had been ok. I stopped immediately & got it recovered home (it was either immediate recovery or 2-3 hours for mechanic to look first!!) Water all over engine bay & full of steam. It was difficult to tell where it was coming from.
First chance today to look at it. I refilled system & got about 11 litres in so have lost the whole lot. Now when I turn engine over (its a poor starter so i haven't even got that far) there is a fountain of water from the expansion tank (cap was off). If I put cap on it is still forcing it's way from underneath the cap. Should there be that much pressure when starting up as I haven't seen that on any cars before.
No sign of 'mayo' on oil filler & rad is less than a year old.
Are things as bad as I fear - ie head gasket etc etc?? Somebody please tell me I just need a new expansion tank cap!!!

Looks like head gasket
sorry to be the bearer of the bad news
get the head crack tested (about 30 quid) and check the front cover gasket on the power steering/alternator mounting is not leaking as this can be the most common cause
gaz

The cap allows water out when theres too much pressure. It sounds like head gasket to me but I'm no expert.

Head gasket gone in a big way I'd say if it's spurting water out of expansion tank - if the cap didn't allow the water out something else would have to give such as water hose etc .
Also if it's left for a while water could get into the cylinder/s and cause hydraulic lock i.e. engine won't turn over and to try forcing it would not be a good idea.
Hopefully head is not cracked but the Tdi is not very tolerant of overheating .

Pretty much as I expected - you just always hope you've got it wrong!!
Cheers for the advice.

That happened to me this summer my 300tdi blew its head gasket on a long run towing a horse box, it transpired that my water pump had a small leak and the expansion tank ran dry, it really made me f***ing sick, I'm not usually that thick! So make sure your system hasn't got a leak when you get your gasket done.

I too had this problem on my disco 300 tdi and cooked the cylinder head, so I rebuilt the engine and since when i am on the motorway i try not to put my foot down because the temp goes up realy quickly and drops just as quick when you take you foot off the throttle and coast a bit, i have done this a few times now but i try and keep an eye on the temp gauge and when it creeps up back off, i have a friend with a 300 tdi in a defender 90 and he fitted three electric fans to curb this temperature rise at high revs and it seems to be working, i think the top and bottom of it all is the engines have a design fault !
Regards
Mark...

i think the top and bottom of it all is the engines have a design fault !
Regards
Mark

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BOLLIX!! the 300tdi engine is the "Dogs What Not's".I hammer our 300tdi down to Spain at least 2 times a year and have only seen the temp needle move once above the gauge middle and that was going up a steep hill on the motorway at 80+,5 passengers & baggage in 35°+.

The fast majority of head gasket failure is cos people dont check there water level/or leaks often enough.

As for you and your mates defender either your radiators blocked/knacked internaly or your fins are blocked with mud through off-roading and not letting air through to cool it down.Get a hose pipe, air line on it!!

I'm currently running mine with out a viscouse fan (cos it's winter) with out any probs, even with a 1t trailer!!!!!!!!

Jason2 said:

BOLLIX!! the 300tdi engine is the "Dogs What Not's".I hammer our 300tdi down to Spain at least 2 times a year and have only seen the temp needle move once above the gauge middle and that was going up a steep hill on the motorway at 80+,5 passengers & baggage in 35°+.

The fast majority of head gasket failure is cos people dont check there water level/or leaks often enough.

As for you and your mates defender either your radiators blocked/knacked internaly or your fins are blocked with mud through off-roading and not letting air through to cool it down.Get a hose pipe, air line on it!!

I'm currently running mine with out a viscouse fan (cos it's winter) with out any probs, even with a 1t trailer!!!!!!!!

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Absaloootly bang on mate I have one as well and it never overheats, an ave got the fan off and waiting to get my kenlow fitted next year. ffs three fans who ya kidden here. perhaps its one of them tits with ten spots accross the grill an all that other ****e.

Yer think i'm rude.

Trouble with the 300Tdi is the temp sender is high in the system and if the level drops too far it isn't actually in any liquid at all! So, gauge can read normal with little or no coolant in the system........BANG!

My 300 blew the head gasket a few years back on the M23 at 80mph!
She boiled to with in an inch of its life!

Found that the expansion tank had split round the seam, apparently common problem, dumping the water and boiling up.

I nursed it onward and then home, using and loosing some 40 litres of water and covering 120 miles!

Every garage locally shook their head and wanted drugs money to crack test the head, skim and all sorts to repair.

me and my mate took the head off, ran a glass straight edge over it, wacked it back on with new head kit and it has covered 40,000 miles more with out fault.

Engines must be near bullit proof, its a simple DIY job if you know your way around a basic engine and have time and some tools.

OM

Having changed many head gaskets over the years I would never put back a head that has been subject to overheating without having it crack/pressure tested because it costs so little .
If you put it back without testing and it is cracked you will have to do the job again plus a new head gasket etc . - so its putting a lot of extra work on you even if you do it yourself .
I got caught twice by putting back a head that was cracked while on the other hand only two of the many heads I have had tested were cracked .
As regards skimming I used to check heads using a piece of thick plate glass and sandpaper but again for the sake of what it costs I don't bother any more .

it seems that the position of the temp. sender is a common problem. would it be possible to fit an auxillary one picking up the temp, from somewhere else?

rickdulas said:

it seems that the position of the temp. sender is a common problem. would it be possible to fit an auxillary one picking up the temp, from somewhere else?

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Some bod does a little black box for about 50 quids.

Try and find link if yeh interested!

How about this, a central heating pipe stat usually operates on 240v, but it's only a switch operated by heat, it simply clips over a pipe and could be set to sense increase or decrease in temp and bring a light on. My guess is it will work fine with 12v and if it is fitted to a hose on the header tank could warn you of an overheat situation because you can set the temp it switches at.

Not sure in the overheat situation on the discovery what happens at the header tank, because usually loss of water results in loss of flow, so might be no water at header tank to switch in overheat situation before it's too late. However if loss of water results in temp drop before overheat, and you want to get it before the steamy bit then set the switch to bring on light at low position. This means that until yer motor warms up the light will stay on, but once off if it comes back on, alert. But I think overheat is the best option but where is the best place to sense it??

They are about 20-30quid and my guess is that the black box is one.

Off on hols so will have a peep when I get back, tell me what you think.

The problem with the 300Tdi seems to be that the water pump is located high on the engine - when the water level drops in the header tank it can easily go below the level of the pump and then no coolant is being pumped.
The engine then overheats due to lack of flow and by the time you notice a change in the temp gauge its usually too late .
So the level of coolant in the header tank is the critical factor and if you go to the Difflock site and put coolant level sensor in search you will find details on a sensor which has been developed by a forum member .
As well as the black box you will also need to get an expansion tank cap for a Range Rover as it has a float system in it .
I intend fitting it to my brothers and sisters 300 Tdi's ( one of them had to have a new head fitted a few months ago and I don't want a repeat )

Check expansion tank seams for leaks and thermostat is working.Us mad Irish always try these.