Head or Gasket?

[Aethelric]

continued from this topic http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=34527

Reading other threads on here it seems that if the gasket goes the head usually goes too.
The symptoms I have are that when the engine warms up, that air is forced into the cooling system. At some stage this has been "fixed" by removing the stat and thus keeping the engine cold. I discovered the problem when I fitted a stat. I have had to remove it again to keep running. I don't seem to be getting any steam in the exhaust, and previously to refitting the stat I had done around 500Km without any coolant loss.
Has anyone had the gasket go without the head? And what were the symptoms.

BTW the fact that it does run quite reliably with the stat removed may be a good "get you home" method if your head goes whilst on holiday.

Dave

[Simon Jones]

In my case, the head was fine, but the gasket was the problem. What probably saved it was that it failed on a short run across town. If it had gone on the motorway & the engine overheated, then it could have been a lot worse. I paid £100 for a skim & pressure test. This was much cheaper than just replacing the head on the off-chance that it was cracked. If you do get it pressure tested, ask if they heat it up first as this will help to open up any cracks.

[The Great Pretender]

Reading other threads on here it seems that if the gasket goes the head usually goes too.
The symptoms I have are that when the engine warms up, that air is forced into the cooling system. At some stage this has been "fixed" by removing the stat and thus keeping the engine cold. I discovered the problem when I fitted a stat. I have had to remove it again to keep running. I don't seem to be getting any steam in the exhaust, and previously to refitting the stat I had done around 500Km without any coolant loss.
Has anyone had the gasket go without the head? And what were the symptoms.

BTW the fact that it does run quite reliably with the stat removed may be a good "get you home" method if your head goes whilst on holiday.

Dave

Think your barking up the wrong tree.
If the head or gasket is at fault removing the stat wont stop the engine reaching operating temp, it may (depending on use) make it take longer but it will still get there and if the leak is heat sensitive will pump gas into the cooling system.
What it may do is alter the positive to negative point of the system.

[missfixit70]

What it may do is alter the positive to negative point of the system

Not sure what you mean by that?
What do you think may be causing Aethelric's problem?

[The Great Pretender]

What it may do is alter the positive to negative point of the system

Not sure what you mean by that?
What do you think may be causing Aethelric's problem?

I Think his diagnoses is wrong, it could be many things Kirsty.
Your first question i'm not sure I wanna answer as it ended in world war 3 and locked posts before the Bongo cooling system had a chance be understood and explored by us all. But basically a system has a positive part (after the pump) a neutral point (eg radiator where the flow slows) and a negative part from there to the pump. That is the simple version, as you are aware the negative or suction side will draw air in, the positive side push coolant out.

[The Great Pretender]

U lurking Cheffy?....................

[cheffy34]

Bingo stingo

NO JUST DAY DREAMING

got side lined

Haven't gotta a clue what your talking about But i will go back and read it again and maybe shed some words of wisdom,

[mikeonb4c]

What it may do is alter the positive to negative point of the system

Not sure what you mean by that?
What do you think may be causing Aethelric's problem?

I Think his diagnoses is wrong, it could be many things Kirsty.
Your first question i'm not sure I wanna answer as it ended in world war 3 and locked posts before the Bongo cooling system had a chance be understood and explored by us all. But basically a system has a positive part (after the pump) a neutral point (eg radiator where the flow slows) and a negative part from there to the pump. That is the simple version, as you are aware the negative or suction side will draw air in, the positive side push coolant out.

Well put+++ TGP and that insight should help peeps to work out many things for themselves once the thought has percolated (or is it circulated )

On the subject of pinhole pricks and the drawing in of air, are we stil sound in thinking though that a 'heat pump' effect may also apply. i.e. coolant expelled through pinhole as coolant warms, expands and system pressurises then - on cooling, coolant+air volume contracts creating negative pressure and drawing air in through pinhole - air that stays in the nearest suitable bend/chamber near the leak). Effect over several cycles is to pump out coolant (on warming) and replace it with air (on cooling). This may result in air pockets in the (notoriously capable of cealing them) Bongo cooling pipes/chambers so that althugh the header tank may still show an acceptable level, there is excessive air. Since air expands much more than coolant, the owner may suddenly experience an eruption of hot coolant from the header tank as the pressure rises dramatically and exceeds the pressure rating on the header tank cap.

[bigdaddycain]

Reading other threads on here it seems that if the gasket goes the head usually goes too.
The symptoms I have are that when the engine warms up, that air is forced into the cooling system. At some stage this has been "fixed" by removing the stat and thus keeping the engine cold. I discovered the problem when I fitted a stat. I have had to remove it again to keep running. I don't seem to be getting any steam in the exhaust, and previously to refitting the stat I had done around 500Km without any coolant loss.
Has anyone had the gasket go without the head? And what were the symptoms.

BTW the fact that it does run quite reliably with the stat removed may be a good "get you home" method if your head goes whilst on holiday.

Dave

I know of a bongo in my locale that has been running round with no stat (and diagnosed as "the head's gone") for many months now... There is the slightest whisp of mist from the exhaust when it's accelerated at a normal rate,plus average amount of blue smoke.... Dunno how it's managed to cling on for so long!

[dandywarhol]

Reading other threads on here it seems that if the gasket goes the head usually goes too.
The symptoms I have are that when the engine warms up, that air is forced into the cooling system. At some stage this has been "fixed" by removing the stat and thus keeping the engine cold. I discovered the problem when I fitted a stat. I have had to remove it again to keep running. I don't seem to be getting any steam in the exhaust, and previously to refitting the stat I had done around 500Km without any coolant loss.
Has anyone had the gasket go without the head? And what were the symptoms.

BTW the fact that it does run quite reliably with the stat removed may be a good "get you home" method if your head goes whilst on holiday.

Dave

I know of a bongo in my locale that has been running round with no stat (and diagnosed as "the head's gone") for many months now... There is the slightest whisp of mist from the exhaust when it's accelerated at a normal rate,plus average amount of blue smoke.... Dunno how it's managed to cling on for so long!

That could be coming from the coolant part of the turbo Ste.

[cheffy34]

I reckon i am with you now mr P I understand the ins and outs but i still daren't do my system I assume the flow direction will be the same on all cars and on my v6, stupid i know Mr p but i assume hot water enters the top of radiator and comes out the bottom cooler. I'm not stupid just slow but i am good wive me hands


I would love to stay here and find out but my nieghbour has beaten me at mo and the threat of violence is to much, we are catagorically out of the way this weekend so there amphet and beer fuelled violence doesn't include me again this sat and sunday

asta


Back soon Dar

[The Great Pretender]

Mike I tend to think of the engine as a radiator in a central heating system, feed and return pipes dropping below the rad same as the flow and return on the Bongo. Now any air that floats around the c/h system, when it gets to a radiator what happens, it rises to the top and there it stays and as more air works its way around it starts filling the radiator and normally the first you notice this is when the room is bloody cold.
Now if air gets drawn into the Bongo engine via air leaks or trapped air or a fresh coolant mix giving of air as it is heated. As the pipes have to drop down out of the engine bay the same as a radiator the air ends up in the same place, the top eg the head and there is stays until it is vented, make sense?
Now as the coolant in the head is being replaced by air the header tank level may not drop and this can carry on until the head is so full of air that the coolant level is below the level of the return hose to the rad and then no matter how fast the water pump spins it cant circulate, head heats up fast, fans come on, system presure rises, open the header cap and cool coolant is forced out.
Coolant being forced out of the header tank.............yer heads gone mate.
Heard that before?
So before commiting Harry Carry thinking the head is dead consider the simple things that can cause problems.
And remember.................Always look on the bright side of life.............

[mikeonb4c]

Mike I tend to think of the engine as a radiator in a central heating system, feed and return pipes dropping below the rad same as the flow and return on the Bongo. Now any air that floats around the c/h system, when it gets to a radiator what happens, it rises to the top and there it stays and as more air works its way around it starts filling the radiator and normally the first you notice this is when the room is bloody cold.
Now if air gets drawn into the Bongo engine via air leaks or trapped air or a fresh coolant mix giving of air as it is heated. As the pipes have to drop down out of the engine bay the same as a radiator the air ends up in the same place, the top eg the head and there is stays until it is vented, make sense?
Now as the coolant in the head is being replaced by air the header tank level may not drop and this can carry on until the head is so full of air that the coolant level is below the level of the return hose to the rad and then no matter how fast the water pump spins it cant circulate, head heats up fast, fans come on, system presure rises, open the header cap and cool coolant is forced out.
Coolant being forced out of the header tank.............yer heads gone mate.
Heard that before?
So before commiting Harry Carry thinking the head is dead consider the simple things that can cause problems.
And remember.................Always look on the bright side of life.............

Excellent explanation - well worth noting by all as I think it explains the danger of relying on header tank level alone. It also suggests that temp measuring devices that rely on a sensor immersed in coolant could be fooled, so engine block sensor or (possibly) oil temp sensor might be better bets?

[Aethelric]

Think your barking up the wrong tree.
If the head or gasket is at fault removing the stat wont stop the engine reaching operating temp, it may (depending on use) make it take longer but it will still get there and if the leak is heat sensitive will pump gas into the cooling system.
What it may do is alter the positive to negative point of the system.

That all sound feasible TGP, but I have been running around for around 600Km and had no problems with the stat missing. When I put it in I then got air in the system which I think is being pumped in by the engine, either via the gasket or a crack in the head. This doesn't seem to happen when the coolant is cold.
When I picked up the bongo, I drove it home around 100Km. For the first 40Km I thought the temperature sender was not working, then as I got into slow moving traffic the gauge started to rise - reaching about the 10 o'clock position (a bit lower than a bongo without a Mason alarm). As I got out of the traffic the gauge dropped again to the bottom stop.

Yes, the air will collect in the head, and today I'm going for a run, (no stat) and then after the engine has cooled down, try a "cold bleed". I should see if any air has collected in the head.

It really only makes a difference in the short term, as I use it on a daily basis, for my work so it will need to be fixed, but I want to schedule it in.

I have been quoted £1000 to get it fixed, or £1500 if it needs a new head (all plus VAT). Is that a reasonable price?

BDC, you give me hope

[bigdaddycain]

I know of a bongo in my locale that has been running round with no stat (and diagnosed as "the head's gone") for many months now... There is the slightest whisp of mist from the exhaust when it's accelerated at a normal rate,plus average amount of blue smoke.... Dunno how it's managed to cling on for so long!

That could be coming from the coolant part of the turbo Ste. [/quote]

That's quite possibly in addition to Alan...

I have reason to believe that particulare vehicle hasn't been serviced in 2 or 3 years,so i disregarded the amount of smoke being emmited from the exhaust... It's quite feasible that any other items are also on their last legs, and given that the coolant part of the turbo is also a known fail item on some bongo's, then that could well be the case also...

I have been informed that the bongo in question has been diagnosed as "the head's gone" That's all i know on that score... What i do know as a fact, is that the vehicle does local, short runs only, and seeing as the stat has been removed, this has bought the vehicle enough time to carry on plodding about without getting to the overheating stage before the journey finishes.