Coolant issue, low pressure tank filling up

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chewbacca
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Coolant issue, low pressure tank filling up

Post by chewbacca »

Hi all.

Quick question, that I hope I already know the answer to. Just wanted to run it past the experts on here.

1.9 petrol bus, 1984ish, water cooled.

I presume the low pressure tank completely filling up with coolant, means the valve in the header tank cap is shot?

Replacement here...
https://www.brickwerks.co.uk/t3-parts/e ... 3-oem.html

Just to add, the bus drives fine and doesn't overheat, just had the low water alarm start to flash. Well it would, the coolant is all in the low pressure tank. :lol:

Thanks for the help.
B plate 1.9 petrol bus

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Re: Coolant issue, low pressure tank filling up

Post by silverbullet »

Its not a low pressure tank, it's a blow-off overspill that is vented to atmosphere.
Check the blue cap for cracking of the black insert behind the rubber seal, it's a hidden failure point.
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Re: Coolant issue, low pressure tank filling up

Post by chewbacca »

Cheers for the quick reply, I never know what to call it.

I'll check the cap tomorrow for signs of damage. I've heard of people blowing through the cap to test. Does that actually tell you anything meaningful?
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Re: Coolant issue, low pressure tank filling up

Post by ajsimmo »

i have possible bad news, I'm afraid. The behaviour you describe suggests worse than a dalek cap failure, I'm afraid. It's indicative of combustion gases entering the cooling system, probably via a failed compression seal on one or more cylinders. The clue is that you've had a low coolant warning, so something has displaced that coolant. With a failed cap usually too much coolant flows into the overflow tank due to expansion, but it'll still leave the cooling system fully charged with coolant, and as it cools toward ambient temperature will still suck most/all of the excess back into the header tank. If the hose between cap and overflow tank is porous it's possible to draw air in on cooling, but that would just be expelled again on next heat cycle and there would be no net loss of coolant.
Fingers crossed it's not that.
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Re: Coolant issue, low pressure tank filling up

Post by chewbacca »

Well, I'm even more confused.
New cap fitted, overspill drained to max, header topped up. About half a litre spare from the overspill excess. Points to air/gas in the system i guess, which i'm really not pleased about.
I've run the engine up to temp and for about 10 minutes after, rpm sat at about 2000. Heaters switched between hot and cold every so often.
No coolant movement at all. I'll check it tomorrow and try to find time for a short drive, see if it behaves any differently.
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Re: Coolant issue, low pressure tank filling up

Post by ajsimmo »

Often a failing compression seal will not leak under idling or free revving, only under load, due to insufficient cylinder pressure being created to breach the seal. Under full load the temperature and peak pressure achieved is much higher, and a tiny bubble of gas can be forced past the seal on each stroke. This accumulates over time, increasing pressure in the cooling system and forcing coolant out of the cap into the overflow tank. Some of the gas will flow around to the header tank and accumulate at the top, resulting in the low coolant warning light flashing. On cooling, there is still raised pressure in the system due to the gas, and the expelled coolant cannot return back through the dalek cap.
The real giveaway is if you top the coolant up to brimming (header tank, not overflow), take it for a good fast drive, then let the van cool completely (overnight, maybe), and find there is still residual pressure at the cap when loosened, you've got an internal leak.

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Re: Coolant issue, low pressure tank filling up

Post by a1winchester »

ajsimmo wrote: 14 Aug 2020, 08:49 Often a failing compression seal will not leak under idling or free revving, only under load, due to insufficient cylinder pressure being created to breach the seal. Under full load the temperature and peak pressure achieved is much higher, and a tiny bubble of gas can be forced past the seal on each stroke. This accumulates over time, increasing pressure in the cooling system and forcing coolant out of the cap into the overflow tank. Some of the gas will flow around to the header tank and accumulate at the top, resulting in the low coolant warning light flashing. On cooling, there is still raised pressure in the system due to the gas, and the expelled coolant cannot return back through the dalek cap.
The real giveaway is if you top the coolant up to brimming (header tank, not overflow), take it for a good fast drive, then let the van cool completely (overnight, maybe), and find there is still residual pressure at the cap when loosened, you've got an internal leak.

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Re: Coolant issue, low pressure tank filling up

Post by chewbacca »

All the above makes me very sad.
I've not driven it yet, too busy at work. I give it run this weekend hopefully.

Presuming the above diagnosis is correct, is it a big fix? Most stuff I turn my hands to, but engines...
I've known the engine is on borrowed time since we got the bus, but so far it's just kept struggling on. At the minute, repair would be much more preferable because of cost. It's been fault free since getting the exhaust replaced. (Thanks to Andrew oddly enough, before you moved miles away!)
B plate 1.9 petrol bus

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Re: Coolant issue, low pressure tank filling up

Post by chewbacca »

OK, so I'm back on this thread.

I've run the bus a good few times on 10 mile runs I often have to do, with no issue at all.

We decided to risk Wales this last week, frankly we needed a break from work. Over the longer drive we had the same problems. The bus didn't overheat, but the overspill tank was filled and the low coolant light came on a few times. Either way, repair is required.

So the question is, what is the fix? I've a few friends I can call on for engine help, if its beyond my abilities. I do most stuff on the bus, unless it's big engine stuff or specialist tools are required.
There's the further question on if it's time to swap the engine, it's getting tired, but at the minute money isn't really there. Repair would definitely be preferable.

All advice greatly appreciated.
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Re: Coolant issue, low pressure tank filling up

Post by chewbacca »

a1winchester wrote: 14 Aug 2020, 20:18
I had this on my 1990 AutoSleeper last year. I had it fixed and the engine is as sweet as a nut now. Tappets all adjusted up and quieter now. So good came out of bad.

Any chance you could send me over details of the work you had done?
Was it just a random local garage?
Many thanks.
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Re: Coolant issue, low pressure tank filling up

Post by OldSmithy »

I think this is what could be happening with mine too so I’ll be watching with interest.

If it is the case I’m assuming it is a rebuild or a recon unit. Either of which won’t be a quick or cheap fix but I’m wanting to use the van with confidence so if this is the diagnosis I need it sorting. I’m happy to have a go myself in terms of taking it apart etc but as this is my first big issue only having had the van for a short time may be it is one I’ll need to leave to the experts.

Looking forward to reading other responses. I’m off out for a long drive to see what happens today. I haven’t had the flashing light as yet but have seen some coolant pushed into the tank and not sucked back in on cool down. My only hope is I may not have left it long enough on cool down for that to have happened so will leave it overnight this time to check.

Good luck

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Re: Coolant issue, low pressure tank filling up

Post by chewbacca »

I've found this old thread that doesn't make me feel like its one for me to tackle on my own.

https://club8090.co.uk/forum/viewtopic. ... 7&t=156172
B plate 1.9 petrol bus

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Re: Coolant issue, low pressure tank filling up

Post by chewbacca »

Hi all

So I think the current plan is to look for a new engine.
The amount of oil the engine uses, now combined with this new fault, is pointing me that way. I'm fairly certain we'll be running the van for the foreseeable future, so spending the money to get a good engine seems smart.
I'm not rushing into anything at the minute, but is there any places that can be recommended currently?

I'm probably after supply only, reasonably certain I can fit myself.
I think it may also be smart to look for a 2.1 as opposed to a 1.9? Any thoughts on this please?
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Re: Coolant issue, low pressure tank filling up

Post by Mocki »

ole simmo in the scottish islands for refurb or rebuild i would say ..... 
 
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Re: Coolant issue, low pressure tank filling up

Post by ajsimmo »

Thanks Steve
Just back from the flatlands with a truckload of cases and cranks, including a few 2.1s.
Planning to build a couple of cheaper units from stock (with some recycled parts), so I can deliver two on each run over the water. Happy to put one together for you if required.

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