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Discussion Starter #1
hi, i am new to the forum so firstly hello....

basicly i am buying a lovely condition 307 hdi xsi 137 54reg next week. all seems sweet and never overheated etc and drives lovely..

while i was letting it run for around an hour or so i noticed the water level on the resevoir came up around an inch or so... it was slightly higher than the max line when was cold also slighlty.. from the max line.. now i understand that while the the water heats it expands etc.. i took off the cap whilst was running and it didnt come spirting out or not even too much pressure when opened. i left cap off and got someone to give a good rev whilst looking for bubbles coming up etc but there wasnt any.

so my question is does your water rise etc is this normal.... only as i was a bit paranoid since etc. any help to ease my minds great
 

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I've not specifically looked at water levels - only when the beep goes off to tell me the water is low. I've a leak somewhere, I think around the water temperature sensor - but it's just easier to keep topping up. I'm lazy.

They do say to check the water level when the engine is cold. Which would suggest that the level will move according to the temperature of the engine - ie. up as the water heats and expands.

As you say, probably a little paranoia thrown into the mix.;)
 

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One other thing - I don't get water spurting out either when I take off the expansion tank cap. Not much pressure at all.

It's nothing to worry about.
 
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Never looked to be honest. But water does expand when hot so the level would rise a bit as for no pressure was the engine at operating temp (90 Degrees C ) when you removed the cap? I would be more alarmed if the level was going down and the exhaust was steaming / smoking. Was there any gunk in the oil? If you are still unsure then get a mechanic to look over it eg AA / RAC they do checks of you vehicle before you buy it to help stop you buying a lemon :D Yes they may cost a bit of cash to do but I'm sure it would be cheaper than having to spend £££'s repairing a lemon and if I'm not mistaken you have some come back to them if the car is unsafe / breaks down within a set period of time :thumb:
 

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Discussion Starter #6
cheers mate for the reply.. so its normal for the water to expand as the engine heats basically, only it went quite high so thats why i worried. i searched online and it did suggest that it expands etc. just double checking if anyone with same care etc has this
 

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Discussion Starter #7
no the oil was nice and clear as it should be.. not to dark but looked healthy and of correct level. the temp stayed at 90c in the whole hour had it running. when drove it it did come down slightly as normal and when on tick over up to 90c.. didnt hear the fan kick in but suppose that would only if it was overheating wouldnt it
 
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no the oil was nice and clear as it should be.. not to dark but looked healthy and of correct level. the temp stayed at 90c in the whole hour had it running. when drove it it did come down slightly as normal and when on tick over up to 90c.. didnt hear the fan kick in but suppose that would only if it was overheating wouldnt it
Yeah I have only heard my 407's fan kick in twice and both of those times it was scorching and sat in traffic :eek:
 

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The plastic bottle is not actually a reservoir but an expansion bottle so a rise in water level is exactly what should happen. Some older cars I have driven had the expansion bottle with a removable cap and also had the old style radiator cap on the radiator. On those cars, the pressure in the radiator was always much higher than the pressure in the expansion bottle. The only way I can get my head around the pressure differential was due to the diameter of the hose to the expansion bottle being a lot smaller than the radiator hoses.
 

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Discussion Starter #11
ahh gotcha so its perfectly normal then? the water from cold is above the max line also is that ok? is it worth me getting it all drained and anti freezed etc for the winter coming up...
 

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Discussion Starter #12
we are talking about the same water bottle arnt we lol.. the water coolant one etc.. sorry im not the best when it comes down to mechanical terms
 

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We are talking about the same thing.

I think the max line at cold is set to allow for a certain amount of expansion and an increase in pressure. If the level is above the maximum at cold, then the amount of expansion would create a higher pressure than if the level was correct. This increase in pressure could affect the amount of expansion causing higher pressure in the whole system which could result in damage to seals etc. I don't know if modern engines have them but 30 years ago, engines had core plugs in the water jackets which got unseated when the coolant pressure got too high which resulted in coolant pouring from the sides or back of the block. The ones that popped out were usually in a position that required the engine taking out to replace it. a common one on fords was just behind the flywheel which could be done by dropping the gearbox.
 

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ive topped mine up in the past right upto brim and never had any trouble. as stated above many times water expands when hot. also got your thermostat opening when it gets real warm so more water is in the system (coming from what was behind thermostat) :thumb:
 

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First thing I would do, (not because of what you have described, just because it is a new car and winter is on it's way) is to pop into one of the fast fit garages and have the coolant tested.

It is a common problem to find that prior owners have topped off the system with water, diluting the coolant over time until freeze protection levels drop off. Corrosion protection reduces with age. It is good practice to renew every 2 years, and not recommended to mix coolant types.

The 2 important things are the level of anti-freeze protection provided by the system, and the level of corrosion inhibitor in the system.

If either are no longer up to the job replace the coolant, making sure to use the correct type.

If all is good, then I would simply remove a little from the expansion tank, so that the level was halfway between Min & Max when cold.

NEVER OPEN A HOT SYSTEM. EVER.

Coolant in a pressurised circuit can exceed the boiling point of water, and when opened, can gush out and give severe scalds. (Modern engines see close to 2000°c at combustion, and coolant temps up to 120°c.)

Older systems had a pressure cap on the actual radiator which would allow excess pressure to be relieved as the temperature increased. This would lead to a low rate loss of coolant.

Modern systems are sealed circuit, with the expansion being contained within the expansion tank, then being sucked back into the circuit when cooler.

There is under normal circumstances, no pressure relief in sealed circuits at working pressure, although most have a cap on the tank that would pop under potentially damaging circumstances, venting to atmosphere. Normally, these would need to be replaced after the system is fixed.

The pressure within a circuit will remain constant (exception being a slight difference on a cold engine before the thermostat has opened when the engine side is hotter than the radiator side, but at this point, they are technically two circuits, and slight variations due to pumping losses).

The expansion rate of the coolant has been accounted for, so as long as you are within the marks, you should be fine. This is assuming the mix is correct, and the circuit is indeed sealed. A weak mix (or a too strong mix), or leaking circuit could cause the coolant to boil over, but that would be obvious, as well as leading to losses.

Core plugs are not primarily designed to relieve any excess pressure from the coolant system. If they were to pop when the engine was hot, then the result could be disastrous, although it does happen from time to time.

They are also known as freeze plugs. The are designed to "fail" when the water expands due to freezing to protect the block from cracking that could result.
 

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Core plugs are not primarily designed to relieve any excess pressure from the coolant system. If they were to pop when the engine was hot, then the result could be disastrous, although it does happen from time to time.

They are also known as freeze plugs. The are designed to "fail" when the water expands due to freezing to protect the block from cracking that could result.
Well, I've learned something new but it makes a lot of sense. I've only replaced two of these, both on fords and both failed when the temperature was well above freezing. I was This was 30+ years ago when I was an apprentice and the explanation I was given was they popped out due to excess pressure. Your explanation seems the more logical as water does expand as it freezes.
 

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Well, I've learned something new but it makes a lot of sense. I've only replaced two of these, both on fords and both failed when the temperature was well above freezing. I was This was 30+ years ago when I was an apprentice and the explanation I was given was they popped out due to excess pressure. Your explanation seems the more logical as water does expand as it freezes.
Yeah, Although that was not the idea,it is not unknown on older motors.

Back in the day they used cast iron blocks, with stamped steel core plugs, as a lot of American motors still do.

Modern motors are mostly alloy blocks (and often from one piece CNC) with stamped steel plugs.

Due to the different expansion rates, of cast and steel (as well as crapper manufacturing tolerances!), they would occasionally loosen off, and could literally fall out.

With the move to alloy, the tendency is that they remain tight when the engine is hot, and slightly less so when cold, so they are waertight, but would still pop if need to protect the block.
 
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