Disco V8 overpressure in the cooling system

Hi, Hope someone can help... had an interesting fault today (in the hot weather)... Drove some 45 minutes and no problems, driving in traffic for a bit, suddenly steam from the header tank.... and quite a bit too...

Top pipe was solid and loads of steam and water under hgh pressure and after venting a GOOD amount, i refilled the header and rad, and then drove home normally - again 45 minutes+....

But the temperature gauge never got over half and never does... but it tends to vent the water occasionally...

I have had a new water pump last year when it overheated and the engine was re-built with a complete set of gaskets... I have also replaced the header tank cap as i have had caps pressure valves fail before... but ths has got me...

So any ideas would be very helpful!

Thanks All!

a hydrocarbon test is the first port of call i think, if its pressurising from the cylinders rather than just from collant steam then i would say it would have overheated again pretty soon after the first event.

as its overheated in the past i would certainly prepare for liner problems, dont panic tho cos it may just be the rad that is clogged.

after the hydrocarbon test i would clean and flush the rad inside and out, or better still replace it!!

blocked radiator?

is the rad hot all over once engine is up to temp?


is the water getting pumped all round properly after the water pump was fitted

Sounds like classic symptoms of head gasket failure to me.

If it isn't head gasket I'd be surprised; my rangie never overheated but I did have over pressure and water being pumped out of the header tank. Changed head gaskets and problem solved, they'd lasted just 10,000 miles. I suppose it just depends how badly the gasket has failed - it doesn't take much.

The only other thing to try perhaps is back flushing the cooling system and also clean you radiator.

Ok so an update...
I have flushed the entire cooling system through and got rid of a fair amount of rusty water, also back flushed rad and then flushed normally. again filled collent back up to the top of the rad (plug removed) and then started engine to warm and bleed the system, so then topped up again and plugged and cap replaced.

Went on holiday and drove for some 2 hours with short breaks to fill with lpg, and no problems, all on motorway and major A roads. Got to a bottleneck aon the A21 and in the slow traffic, notice the steam from the bonnet.
so pulled over manually vented the pressure and topped up the system again.
From then until i got home there were no problems with overheating - though the journey home in the evening was a lot cooler.

And for the next week it was fine. So i checked all the fluids again on the friday last week, and towed my caravan some 1 hour down back roads - not main ones and then pottered around locally and towed the van home to - very hot weather all weekend. Then monday i towed the van over to the storage place and when i backed up the van into its space, started to vent steam and water... so same process, vent presure and re-fill.... and its been fine today...

But this is still an issue that i cannot keep filling up when the suns out, or i have done some hard work in the truck...

The fans always come on (as i fixed these a few weeks ago)
the vehicle never gets over half way on the temp gauge,
there is no thermostat - binned that as not really required! lol
and the water pump is working fine...
not mixed fluids - but like all land rovers, leaks oil but is regularly checked...

so any more ideas?

i might see if i can get the cylinders pressure tested to see if there are cracked liners as someone has suggested this to me, but surely it would pressurise the system evertime the engine was run?

thanks again

The V8 is a lovely lump but can be a pig to diagnose cooling problems on. I had a 3.5 that pressurised it's system but a hydrocarbon test was inconclusive, a compression test didn't show up any faults, there was no overheating & only slight water loss. It was only when water started to get into the sump that I knew what I was up against. On the same note I ran a 3.9 with a slipped liner for weeks without any problems, other than the bloody tapping! Good luck, assume the worst & if it's not as bad you'll be a happy man.

sounds like airlock or HGF.. unlikely to be an airlock with no stat unless you are forgetting to open the heater controls when you fill it up... LR suggest 1/2 open rather than fully.

hi new to the site and found it interesting.
had a similar problem tonight with my V8. The temp gauge went up and it was boiling over out of the header tank. My neighbour brought water out and topped it up, and we managed to limp home. I am hoping it isn't the head gasket !!
Does a waterpump go often on the v8?

In this hot weather drive with one eye on the temp gauge. There should not really be a problem if you have a viscous fan in working order provided your rad is clean and clear (inside and out) but they can get a bit hot in standing traffic.

If you have electric fans (Kenlowe or similar) they will be working over time, watch out for cooked wires, relays and switches.

As soon as the needle starts climbing above half way pull over switch off engine. Put heater on max heat and run heater fan this will draw heat out of the system (make sure you have some jump leads, you could flatten the battery enough for it not to start). In the alternative, get the vehicle moving to get air flow through the rad. With these temperatures, the engine getting hot may not necessarily be an indication of a problem but if you let it get too hot then expect some sort of trouble later.

and check for leaks... the last thing you want is a slow drip of coolant leaving your system dry and causing far greater damage..

hi new to the site and found it interesting.
had a similar problem tonight with my V8. The temp gauge went up and it was boiling over out of the header tank. My neighbour brought water out and topped it up, and we managed to limp home. I am hoping it isn't the head gasket !!
Does a waterpump go often on the v8?

Click to expand...

Water pumps do go and are a very easy repair, hoever there are 3 different types so remove yours first to get a new one as my parts supplier sent me all three to eventually get the corect one...

and check for leaks... the last thing you want is a slow drip of coolant leaving your system dry and causing far greater damage..

Click to expand...

I have checked as many is i could, and did find the O rings on my vapouriser to be leaking, but a small drip will make the system boil... but havent found any more...

The truck has been fine for a week again but again its not been too hot... and as i said in my earlier posts, my temp guage never gets over half before it blows...

so still looking at the water system - have noticed one odity - when both heating controls are on cold and the fan is on, there seams to be quite a bit of heat coming from the lower drivers (rhd) air vent on the centre console and the console itself is hot!

Hi
My v8 ran well on the open road, but got very hot when in traffic, it turned out to be the radiator although it looked fine on closer inspection the vanes in the middle were rusted so not disipating the heat. Recore rad was about £120.

We have just got our Disco V8 back on the road after a short motor was fitted. It would overheat from cold to boiling in a couple of miles, so fairly obviously it had a problem!

One of the things that is not often mentioned is the coolant mix and type of coolant.

LR say 50/50 mix of OAT type fluid, which is sold in Halfrauds but cheaper from a main LR dealer in 25 litre packs. Watch out also for the ready mixed stuff, it's even more expensive!

The Disco 2 has to have the header tank elevated on the hoses to as far as it can be lifted, and the system bled from the top hose vent.

The pressure cap has to be tight. Keep the level just over the seam on the tank by about 10mm.

Assuming that we had a block or liner problem, then our problems seem to be over. We used composite gaskets on the rebuild, the steel ones didn't look convincing to me! and we have gas as well as petrol (Zavoli Multipoint)

We have done 200 miles since Sunday, and will be going to Newark on the weekend.

Peter

Hi

Any news back on this per chance?

I ask as my newly acquired 1999 V8 Auto Disco II is doing the following:

- Once up to running temp, if you slow down to a slow speed for a couple of mins, the temp gauge can race up - in literaly a couple of secs. The pressure then clearly blows a stack of the boiling coolant out.

A cool down and de-pressurise, and top up of water, and off you go again.

It is very strange.

With a very good mechanic we have ruled out most things:

Fans - working a-OK, further proven by taking all of the thermostat workings out - now it's hard to get the electric fan to cut in (in this weather anyway!!).

Viscous tested every which way and fine.

No coolant leak (until it boils), have done a few hundred miles, so rules HGF out.

What we did notice though is that heat is uneven around the engine. With the car idiling, top pipe gets hot, the rad gets hot, matrix hot. Then you (carefully!) put your hand down past the thermostat on the radiator and the bottom has gone cold. Weird.

I hear you saying blocked radiator - it isn't!

We did the old test of filling up the radiator with the top and bottom pipe off, your hand covering the hole the bottom pipe left. The water gushes out - with a hose with strong pressure you can't fill it fast enough!!

So to aid the issue, we fitted an electric water pump from an Omega - initially into the pipe returning off the heater matrix. Did 70 miles in all sorts of conditions (cruising, racing, stop start). Sure enough, in the end she blew, the same as before (fast run, then 400 metres behind a horse, gunned it once past, and she quietly wet herself with the gauge racing).

So, moved the electric inline pump down to go into the pipe into the bottom of the radiator - lower down, and not at risk of running dry like the higher point in the matrix was).

She wet herself again in similair conditions.

This has really got us now.

As far as we can see, something is really stopping circulation. We have had the water pump out, and it seems fine. We will check the part with LR and maybe replace with new to see.

Certainly, despite efforts, water just doesn't want to circulate.

The car has done 90k miles, but has been serviced with a coolant change regularly.

Any other ideas??? I am down to two issues:

1. The water pump looks and feels ok to handle, but may be dead, or indeed may have been changed for the wrong one (previous comment mentions there are three types)
2. There is something in the engine preventing circulation big time - something flapping around, so it makes the top boil.

A cracked pipe may be possible, but we can't reconcile how that would cause such a sudden temperature rise??

Any ideas and thoughts welcome. If not I hope the above list maybe helps - as it is worth checking all of the above, but there aren't many other things to do or change other than engine.

Head gasket?

hi i am having the same problem just had a new head gaskets done new water pump and done less than 50 miles and i pulled up at asda while i was getting some cash it blew a coolant pipe replaced this and i have noticed it is building up pressure in the top hose going to the thermostat
i am getting concerned about it incase it goes with a bang

First port of call is to have a sniff test done of the cooling system.
If that is inconclusive then it will be heads off and a pressure test of the cylinder block to ensure it is not a cracked block or a slipped or porus liner.
Removing the plugs if they are not new will show if it is using coolant as the steam effect will wash the carbon off the plugs and the valves and piston crown.

On the 300 series dash it is very rare for the temp gauge to wonder over normal trust me I have had two customers cars with overheating issues and the gauges showed normal until the engine blocks were replaced as they had pours blocks

On the d2 I would guess at either sticking thermostat water pump fault or a pours linner or head gasket
I am currently fixing a forum members engine it has a slipped linner which was badly stained enough to show when taking the heads off and it has just had a set of top hat liners and refaced heads too

Hi there,

I was having a mysterious problem with over heating, changed thermostat etc...
it turned out to be a blocked return pipe in the expansion tank, so i replaced the tank and the problem was solved.

Until the next problem arose............................lol

Hi,
I know this is an old thread but I have the same problem as Bigmattreid on my disco mk1 v8 3.9 and wondered if there was any update on the final diagnosis / fix?