Coolant Pressure playing silly buggers!

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300CE
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Coolant Pressure playing silly buggers!

Post by 300CE »

Not sure what is going on with my van at the mo, but have the following dilemma:

If I go for a run and up to temp, the coolant level in the header tank drops down to minimum and the light starts flashing. It never goes any lower than minimum no matter how long I drive for and the temp needle doesn't rise.

If I let the engine cool down it doesn't pull anything back into the header tank from the top up tank, but if I undo the header tank cap, you hear the pressure release and it fills back up to full? I can leave it for a couple of days and it will still do this.

She doesn't smoke/steam (steams about 5 minutes from cold until warmed up and is then clear) and uses no oil whatsoever (I've never had to top up between oil changes) and it's always full on the dipstick.

I've replaced the darlek caps and now have a genuine one on there, I've also cleaned out the top up tank and it has a new pipe from top up tank to darlek cap. The heater works really well and is nice and hot.

Could this be a possible thermostat problem (sticking) and/or could it be an air lock and requires re-bleeding?

Any ideas much appreciated!
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Smiffo
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Re: Coolant Pressure playing silly buggers!

Post by Smiffo »

I wiped my last reply - it was nonsense..!!

OK. If the coolant level is going down in the header tank when you drive it, then it must be going somewhere, so you must have air in it.
Mine does this when I'm bleeding it.

I have to rev it right up to drag the coolant level down while I top up the header tank.

So, did you rev the nuts off it when you topped up the coolant level?

Also, when you go back to it and the header level has dropped, is the expansion tank full and over max?
( Or has it remaining higher than before? )
Last edited by Smiffo on 26 Nov 2016, 21:08, edited 1 time in total.
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300CE
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Re: Coolant Pressure playing silly buggers!

Post by 300CE »

Cheers for the reply Smiffo! It's been doing it just prior to the stainless coolant pipe change and I initially thought it resolve it as the leaking plastic ones would have been causing an air leak. All connections are the same as before as the pipe connectors were all colour coded so didn't get it mixed up (my brain isn't what it used to be) :lol:

I've had a search about but can't seem to find anything with these exact symptoms and wondered if it could possibly down to the failing stat maybe being stuck open?
Last edited by 300CE on 26 Nov 2016, 21:10, edited 1 time in total.
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Smiffo
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Re: Coolant Pressure playing silly buggers!

Post by Smiffo »

Sorry mate - I edited the post before you replied.
I think I was going off on a tangent....

Here is my edited one below:

Smiffo wrote:I wiped my last reply - it was nonsense..!!

OK. If the coolant level is going down in the header tank when you drive it, then it must be going somewhere, so you must have air in it.
Mine does this when I'm bleeding it.

I have to rev it right up to drag the coolant level down while I top up the header tank.

So, did you rev the nuts off it when you topped up the coolant level?

Also, when you go back to it and the header level has dropped, is the expansion tank full and over max?
( Or has it remaining higher than before? )

Lets get the basics first - the exact symptoms etc and steps followed
Not sure about stat being stuck open. If it was that which would cause these symptoms, there would be all those people driving around with no Thermstats in the van with odd symptoms like yours ( I think? )
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300CE
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Re: Coolant Pressure playing silly buggers!

Post by 300CE »

No worries Smiffo - the expansion tank coolant level stays exactly where it is (between min and max) - it doesn't look like it's actually pulling anything in or pushing anything back out. That said, when I went on a really long run, the expansion tank had filled up to over max, but, the header tank was almost full to the brim?

When I bled it I revved it up to about 3000rpm.

What I did notice is singular air bubbles rising up in the expansion tank which would stop if i pulled the pipe off of the darlek cap?!
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Smiffo
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Re: Coolant Pressure playing silly buggers!

Post by Smiffo »

It does sound like air in there, doesn't it...

If we imagine it is a closed system, and if you definitely aren't losing any coolant through leaks, then it must be going somewhere for the header tank to drop ( even when expansion tank remained the same. )
I would try bleeding again first before getting bogged down, I think.

Silly question, but did you undo the nut ontop the radiator when bleeding?
( Tell me to Feck oof if that was a dumb question LOL )

Also, I'm not sure if you have an early or late cooling system....?
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300CE
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Re: Coolant Pressure playing silly buggers!

Post by 300CE »

:lol: A silly question is only one that isn't asked mate as it's usually the obvious ones that end up being the culprits!

Yep, all bled through the rad screw as well. Could well be that it needs re-bleeding but I have a spare stat I can use so might just change that anyway prior to the bleed - I think i put a GSF one in there when I replaced the engine about 3 years ago.

I have the late cooling system :ok
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itchyfeet
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Re: Coolant Pressure playing silly buggers!

Post by itchyfeet »

pin hole leaks can act like one way valves and give you strange results
some leak cold some leak hot
tighten all clips :ok

they don't call them water leakers for nothing :lol:
Last edited by itchyfeet on 26 Nov 2016, 21:38, edited 3 times in total.
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Smiffo
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Re: Coolant Pressure playing silly buggers!

Post by Smiffo »

I suppose changing the stat is cheap and easy on the late ones, and you would bleed it after anyway.

Still thinking - it can't be anything else other than air in there from the start.
If it was fully bled, the only way air would get back in there would be if the coolant expanded and leaked out, and then sucked air back in through that leak when it subsequently cooled down and contracted...

Someone may pick holes in that theory.
I haven't experienced it myself, but that is how I would imagine air to get in the system if it were bled fully to start with.

Which of course means it could be leaking and you can't see it / find it?

Let us know how you get on..!!
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300CE
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Re: Coolant Pressure playing silly buggers!

Post by 300CE »

Cheers Smiffo/Paul - much appreciated chaps - I'll do the change next week, check all pipes and clips and provide an update! Bloomin' vans, just when you think your on top of everything they let you know that still crave attention :lol:
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Smiffo
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Re: Coolant Pressure playing silly buggers!

Post by Smiffo »

No probs - I'm just suggesting ideas really for you.

Anyway, I hope it works out for you..!!
Thinking a bit more, I would hope it isn't a leak. It would have to be a pretty big leak to let out enough to have the coolant drop enough for the LED to flash....

In that scenario you would like to think you would see it leaking from the system.

That says air in the system to me really - but again this is all theory based, I haven't experienced your issue.

Just an FYI, if you don't have a rev counter, you will be surprised how much you have to rev the van up to bleed it... 3000RPM sounds like it's going nuts... If your misses doesn't come out and ask what on Earth you are doing, then you aren't revving it enough..!! :wink:
You should also see the header tank level drop dramatically when you do that, so you need to top it back up and put the dalek cap back on before dropping the revs. If you don't, you end up with a nice stain on your drive - like me :lol: :lol:
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300CE
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Re: Coolant Pressure playing silly buggers!

Post by 300CE »

Thanks again Smiffo - I have a rev counter fitted with me little red marker on about 4.2k and you're right it does sound like it's going to take off at 3k! Like you said makes it sound like air in the system as that long run i did where the expansion tank went over max was on the motorway so would have been at a constant 55-60mph which is about 3000/3200 rpm in 5th, so maybe it forced the coolant through.
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Re: Coolant Pressure playing silly buggers!

Post by kevtherev »

Is the bleed ring clear with no blockages?
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Re: Coolant Pressure playing silly buggers!

Post by itchyfeet »

you did open the hearter valve when bleeding didn't you? lots of air in that circuit.
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300CE
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Re: Coolant Pressure playing silly buggers!

Post by 300CE »

Cheers chaps - yep, bleed ring is all clear as have a new one on there. Pretty sure had the heater valve open (was a few months ago now) but will ensure on the re-bleed :ok
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