Expansion tank
- Thread starter stina
- Start date
GRTV8
Well-Known Member
Sorry to harp on about expansion tanks ,I know its been done to death , but cant find a thread that suits .[ pun]
I need a little headway here.
It was rather warm today and a quick 20km around the main highways of west Auckland was too much for my radiator .Temp gauge was normal .
I pulled up for a cafe and P6b dropped a noticeable amount of green stuff in the car park . A few concerned patrons pointed the fluid out and I thought " Im over this regular display of water works"
Had my cafe and drove straight to a landrover wreckers and bought a brass expansion tank in good order for $40
Its wide and squat c/f the taller SD1 tank.
Ive got A/C so room is quite tight in the engine bay . One of the a/c pipes is running hard up along the drivers side inner wing ,right below where the tank would be mounted.
Im trying to avoid rubbing pipe and tank.
How high above the inner fender can it be mounted without fouling the bonnet undermat ?
Only problem I can foresee is having to remove the tank to change the spark plugs
Im about to give it a black repaint and fiddle about with mounting it.
The two large mounting legs will require bending to fit.
Anyone out there with A/C retro fitted an expansion tank with out incurring problems ?
I need a little headway here.
It was rather warm today and a quick 20km around the main highways of west Auckland was too much for my radiator .Temp gauge was normal .
I pulled up for a cafe and P6b dropped a noticeable amount of green stuff in the car park . A few concerned patrons pointed the fluid out and I thought " Im over this regular display of water works"
Had my cafe and drove straight to a landrover wreckers and bought a brass expansion tank in good order for $40
Its wide and squat c/f the taller SD1 tank.
Ive got A/C so room is quite tight in the engine bay . One of the a/c pipes is running hard up along the drivers side inner wing ,right below where the tank would be mounted.
Im trying to avoid rubbing pipe and tank.
How high above the inner fender can it be mounted without fouling the bonnet undermat ?
Only problem I can foresee is having to remove the tank to change the spark plugs
Im about to give it a black repaint and fiddle about with mounting it.
The two large mounting legs will require bending to fit.
Anyone out there with A/C retro fitted an expansion tank with out incurring problems ?
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keynsham1
Active Member
I need an expansion tank for my V8 NADA car but there is absolutely no room in the engine bay. It is not necessary to have a pressurised expansion tank provided that the radiator cap has a seal in the top to stop air being sucked in. If you just stick the breather hose in a bottle, the expelled water will be pushed into the bottle and then sucked up again when the engine cools.
To this end I have been searching for the ideal container and have found it. A Halfords bicycle drinking water bottle. It even comes with its own mounting cage! The best part is that it can be mounted under the front wing just behind the back of the front sidelight. It is functional and out of sight!
To this end I have been searching for the ideal container and have found it. A Halfords bicycle drinking water bottle. It even comes with its own mounting cage! The best part is that it can be mounted under the front wing just behind the back of the front sidelight. It is functional and out of sight!
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Phil Robson
Well-Known Member
I'm interested in fitting an expansion tank myself, but I can't fathom how water is drawn back into the radiator when the engine cools.
The overflow pipe exits above the sprung cap seal - how does this let water return? :?
The overflow pipe exits above the sprung cap seal - how does this let water return? :?
Phil Robson
Well-Known Member
Ahh I see! That now makes sense Hans, thanks. 
happy days
Active Member
Hi Will, looks good and is a definite improvement, no need to keep topping up. keep an eye on your brake fluid level by the way. that enginre bay does look clean, if your cleaning because your bored mine could do with a bit of a spring tidy up
keynsham1
Active Member
I will try to explain! Normally, the cap (old style) has a spring and a seal. This seals below the level of the drain pipe. There is no real proper seal around the cap to filler rim, just usually a lightly sprung ring. When the water heats up, it expands and the pressure in the system increases. When it get to its max working pressure, the seal below the drain pipe opens against its spring and the water can go out of the drain pipe. It doesn't come put around the cap edge as the thin lightly spring ring stops it. When the engine cools again, it sucks air back into the radiator past the lightly spring ring (and up the drain pipe I expect) and throught a one way valve in the middle of the cap which lets air in but not out.
If you fit a proper rubber seal around the cap to rim area then when the engine cools the only way air can be sucked back into the radiator is up the drain pipe. So if the drain pipe dips into an open bottle, then expelled watrer is pushed out of the radiator into the bottle, and when the engine cools, provided the drain pipe end is below the water, the water will be sucked back into the radiator.
That sounds complicated, but I assure you it isn't really!
If you fit a proper rubber seal around the cap to rim area then when the engine cools the only way air can be sucked back into the radiator is up the drain pipe. So if the drain pipe dips into an open bottle, then expelled watrer is pushed out of the radiator into the bottle, and when the engine cools, provided the drain pipe end is below the water, the water will be sucked back into the radiator.
That sounds complicated, but I assure you it isn't really!
Phil Robson
Well-Known Member
I do understand now - thanks
It is interesting that the 3.5 litre P6B engines and possibly the SD1 engines too have a bad habit of discharging coolant from their respective radiators, hence the valuable contribution that an expansion tank can make. Looking back through my log book for work carried out on my Rover since 1978, the need for frequent topping up of the coolant was always ever present. Distances varied but typically 1 to 2000 Miles was the normal range. When left for longer the level down was sometimes quite significant with half the radiator empty. Coolant loss was independent of the thermostats fitted, 74, 78 and 82 were all used over the years, radiator caps all 15psi and different brands made no difference. Increasing coolant capacity by using a 3 core as opposed to the original 2 core design did not prevent the purge either nor did changing from tin to composite head gaskets. Blown head gaskets will certainly see considerable coolant loss, much more so than what is normal for these engines, but that is down to component failure rather than a possible design issue.
My 4.6 on the other hand doesn't display this problem at all. I checked my coolant level for the first time on December 15 having travelled 16,446 Miles since May 1, a new radiator I fitted at that time. The coolant level was as it had been when it was filled, engine off..right at the base of the filler neck, engine running...an inch down at most. So no change and no loss of coolant, interesting.
I wonder if the 10.5 : 1 engines like my original are the biggest offenders? Is the high compression ratio the cause or does it stem from the P6B heads? Does a P6B engine fitted with any of the later 14 bolt heads behave the same? I tend to think it stems from the high compression and the additional heat that generates as a result when the engine is switched off, but I have no proof.
Ron.
My 4.6 on the other hand doesn't display this problem at all. I checked my coolant level for the first time on December 15 having travelled 16,446 Miles since May 1, a new radiator I fitted at that time. The coolant level was as it had been when it was filled, engine off..right at the base of the filler neck, engine running...an inch down at most. So no change and no loss of coolant, interesting.
I wonder if the 10.5 : 1 engines like my original are the biggest offenders? Is the high compression ratio the cause or does it stem from the P6B heads? Does a P6B engine fitted with any of the later 14 bolt heads behave the same? I tend to think it stems from the high compression and the additional heat that generates as a result when the engine is switched off, but I have no proof.
Ron.
Compression ratio per se cannot be the cause. But I could believe some quirk of the coolant passages in early 3.5 blocks and heads could be to blame. Anyone with SD1 heads on their P6 still have the problem? I presume, Ron, that you used the original inlet manifold? If not then the efficiency or otherwise of the bleed system up through the carburettor tower could be a cause? Early manifolds having the problem, later not? I do know that the SU inlet manifold does go through at least a couple of casting numbers over the years.
Chris
Chris
Willy Eckerslyke
Well-Known Member
Keynsham's explanation also covers the Land Rover Series 3 system that puzzled me as it didn't look as if it should work.
This uses a narrow overflow bottle and comes with its own carrier so might be a better and more robust solution than the Halfords one above.
This uses a narrow overflow bottle and comes with its own carrier so might be a better and more robust solution than the Halfords one above.
chrisyork wrote,...
Hi Chris,
Yes, the original inlet manifold from 1974, and the tower bleed system has always been kept clear with strong coolant flow into the radiator.
So with the later manifold design and no tower blockage the problem was still there when on my original engine. It could be something to do with the coolant passage design within the block, and maybe the heads too... :?
There needs to be a reasonable amount of feedback from members so as to see if this plays out.
Ron.
Hi Chris,
Yes, the original inlet manifold from 1974, and the tower bleed system has always been kept clear with strong coolant flow into the radiator.
So with the later manifold design and no tower blockage the problem was still there when on my original engine. It could be something to do with the coolant passage design within the block, and maybe the heads too... :?
There needs to be a reasonable amount of feedback from members so as to see if this plays out.
Ron.
vaultsman
Well-Known Member
Since Feb '09, Occie (one of the last 10.5:1's) has had mid-80's Range Rover inlet manifold and heads...
...and she still divests herself of some coolant...but nothing like as much as with the original heads/manifold. So...could be a block issue. Or maybe just clearer coolant passages after the top end rebuild. Or slightly lower CR after the composite gaskets.
...and she still divests herself of some coolant...but nothing like as much as with the original heads/manifold. So...could be a block issue. Or maybe just clearer coolant passages after the top end rebuild. Or slightly lower CR after the composite gaskets.
stina
New Member
vaultsman
Well-Known Member
stina said:I think for the few quid it cost to do you always have a full coolant system , about two or three pints more than the standard system seems to want to hold . So why bother complicating things , another couple of pints is always good eh ?
Merry Christmas stan
Indeed! And a few more will pass my lips later!
Merry Christmas to you Stina! :wink: