Does anyone have a link or can explain in detail...

... the flow of coolant around the engine please?
Im after the full flow details, i.e does the cool water come out the top or bottom of the rad (top makes sense compared to where thermostat is)

As in my other threads, the system is perssurised, is it normal to overflow eventually from the expansion tank if the cap is left of whilst running the car from cold to running temp, yes/no?

Where are the temperature sensors and how many?

If the car is clearly not overheating by the gauge, can there still be concerns about efficiency of the cooling? (assuming no HGF / liner problems)

How long before the thermostat opens from cold to start allowing hot water to circulate?


Im just trying to work out whether I need to take my thermostat off or not, radiator out and flush etc, purely due to running up my car from cold to warm with the cap off, and witnessing it slowly rise in the expansion tank then overflow.

if its overflowing then there is something wrong. take the litte pip off the rad, see if its clear to the exp tank, also water should come out of the rad side

Download PDF Range Rover P-38 Workshop Manual | PDFTown.com right click where it says 'mirror' about 1/3rd of the way down on the left just below 'ads by google' click save as or save target as or save link as. ive test the link and it works.

once downloaded, look under coolant system v8 and theres the diagrams of the coolant system!!

best thing to do is take the stat off, its gonna tell you one way or the other. if you do replace the stat, save the old one, it may come in use if you take out the centre with snips/hacksaw blade. you can always fit it back without the gubbins inside if you need to in future!!!

Water expands when heated does it not? The system is designed to run under pressure which raises the boiling point of the coolant, thus if you run with the pressure cap off there could be localised boiling around hot spots in the head, this and expansion will surely cause some water to come out if run from cold to hot with no cap. Depends how full it was when you started I suppose.

Little pipe definitely clear to expansion tank. Easy to test by squeezing top pipe, that shows water coming into expansion tank from the little pipe. Plus when its running there is constant flow.

Bear in mind I have ONLY run the car for 5-7 mins 3 times since the expansion tank emptied due to o-ring leak, since then is when I have seen the water rise above and leak out from a fairly full expansion tank (slightly overfilled)...


Datateak - Well yeah water will pressure and expand under hot conditions, but what is normal is what im trying to establish

mine doesnt boil out anymore!!! it all depends on the amount of expansion/overflow.

there is nothing that can be done until stat is out, plugs are out etc. trust me i have tried loads of ways of avoidind replacing engine!

Ok... taken thermostat off.

Ran water through radiator, came through clean, smooth no probs!

Put thermostat in bowl of HOT tap water, boiled kettle, took thermo out and slowly poured boiling kettle water into back of thermostat (not the rad entry side, but the 3 pipes entry side) holding it upright.
Stat opened about 3-4mm gap around the rim where it closes, water dropped through.
Not the biggest gap, should it open more? Seems a big device to only open about 3-4mm.

Will go and gently heat in a saucepan now to see what happens, but does that give any pointers so far?

All the water that came out car cooling system looked "clean"

In the pan it opened maybe 6-7 mm as the bubbles started and it began to boil up!?

sounds like hg or liners mate i'm afraid!

Right water flows out of the engine through the top hose, and in to the bottom of the engine from the bottom.
Water pump, basically shifts the water, rather than lifts it.
Thermostat closed, water is recirculated round the block and heater matrix; when open, larger bore of radiator hose allows most of it to head to the radiator to get cooled.
Nearly all cooling systems are pressurised to some degree; aftual pressure is usually marked on the radiator / expansion tank cap, where there is a pressure release valve; I think that on old motors the overflow was supposed to open at 15psi or thereabouts.
Systems with an expansion tank, have a higher release pressure, as the theory goes, that any pressure build up is vented into the expansion tank; and when the system cools again, it can suck that water back in.
Not sure what variant of engine you have, of if there is any additional plumbing for LPG or anything; but there is normally a vent on the radiator, and another on the pipe to the heater matrix; roughly the two highest points in teh system, apart from the expansion tank for you to belled any air-locks.
When you fill the radiator from the expansion tank, it doesn't ALWAYS fill the cooling system, and the expansion tank can sit half full or more without the water percolating through to the radiator.
On my Rangies the bleed cap on the heater natrix hose is the easiest to get at and indo, as its metal. One on the rad is plastic, and the plastic hex head is softer than the thread's grip on it..... defied even a six sided socket the other day.... but doesn't matter.
I remove the vent plug, run for a few seconds to expell any air by circulating what water might be in there via the water pump, then top the system up through the vent hole.
I also allow the engine to run for a couple of minutes after filling, with the expansion cap off; getting the engine warm enough to open the thermostat (Hot air out the heater is the acid test, rather than the temp guage). That often bubbles any excess water out of the expansion tank.
Then I'll let in run a while to circulate water througuh the block and rad, and then trn the motor off, and re-check the top vent.
I also have gas on both my motors, with T-pieces off from the heater matrix hose to the evaporator. I check whether the evaporator is actually getting warm, as well as heater; and turn heater to cold and see if it makes any difference to hose warmth; Also pull top run to the vapouriser (its about level with the vent cap) and physically check theres water in it & circulating!)
After refilling or flushing the system, worth keeping an eye on; but expansion tank should only be about half full, it WILL pump up when the engine is running, more when warmed to operating temperature, so that sounds normal, but do by hyper paranoid about air-locks! Ran motors before now, with over-flowing expansion tanks and bog all in the block!

Thanks Teflon and Gav and everyone else who responds.
Teflon, your overview helps. Gav has also given me alot of help and assistance.

Car is all back together, minus coolant right now, got dark.

By pure coincidence, 2 doors down, brother in law of the girl that lives there starts chatting to me about whats going on, took a big interest. He did his apprenticeship with Land Rover, went over the cooling system with me, and said it is perfectly ok that the water rises and overflows when the cap is off. Especially with how mine materialised.
Said very little chance the HG failed and/or liner prob as it's just happened since its been sitting.
Given me details on how to fill it to avoid air blocks, but says until it settles it can and probably will slowly fill and overflow from the expansion tank if the cap is off. It's pressurised and it's hot and expanding.
Definitely knows the V8's inside out, given me loads of info and it all matches up with what i;ve read on here.

So tomorrow I fill it with coolant in the way he has told me too and go from there. Also said that if it hasn't overheated at all, again very unlikely I have HGF.

Appreciate all your feedback...