Overheating problem!

[monfluffy1987]

Hi everyone,

I have just registered on this site, so am probably the newest member!

I have read through numerous overheating issues on the forum and taken what i thought to be the necessary steps to fix the problem... But now I'm experiencing slightly different symptoms. Here's what's happened to me:

after 2 months of having the car (!!!) I saw my temp guage rise considerably so i pulled over only to hear a bubbling noise from under the bonnet. I then checked and saw coolant trickling out of the expansion tank. I merely topped up with water and the problem went away.

This then repeated itself (driving through Germany!), so i called out the breakdown company. The guy topped up with coolant and sent me packing.

Since this, back in the UK I have located a common problem (a hole in the coolant hose as it crosses the engine bay). I then repaired this correctly & cable tied.

I then drained the system as per instruction, and have filled with 50/50 coolant.

I have only driven the car on two short journeys since, but i have found that my coolant hoses are all super hot after driving and my expansion tank is chucking out coolant. (so much so, that i start on 'full' before a journey, get back and leave the car in the drive, Only to check and find that the coolant is on 'low' and the bottle that i put out to catch the over flow in is half full!!! i.e. 1/4 litre!

What's wrong with my car/ where do i take it? I'm from Oxford!

(ps. i have just recievd a mason alarm and will fit tonight).

thanks!

Marc

[Simon Jones]

Hi Marc - welcome to the forum.

It sounds like you may have an airlock in the cooling system which tends to happen if it has not been bled properly. The air will expand as the temperatures rises which forces out the water. Because the system is not running at the correct pressure, the boiling point of the coolant is not as high as it should be, hence it running hot.

There is a wealth of information on here about bleeding the system & there are a few variations on how to do it. Haydn Callow uses a method of bleeding the system which seems to be very sucessful at getting the air out. See this post for details on the steps I used in Poland when I needed to do an 'emergency bleed'.

http://www.igmaynard.co.uk/bongo/forum/ ... re&start=0

I would advise you not to use the van until this is sorted otherwise you risk serious damage caused by over heating.

Don't panic - it sounds fixable.

Simon

[mikeonb4c]

Should the coolant be checked for traces of exhaust gases in case there is a leak in the head gasket and its blowing ito the cooling channels?

[bigdaddycain]

A quick sniffer test wouldn't do any harm mike, but it does sound like an airlock as simon correctly points out....

Are your front AND rear heaters blowing constantly hot monfluffy? If not, that's another pointer to an airlock, especially if the rear heater is just blowing cold/warm.

[bongoben]

When I change my coolant, I test for air in the coolant system several times to ensure that all - or most - of the air has been purged. If anyone wants to try this, here is what I do and is based on the fact that air in the system will be compressed when the coolant level rises in the expansion tank and creates pressure.

Start with a cold engine. Remove expansion tank cap and add or remove coolant so the level is exactly at the MAX mark and then replace the cap. Turn off cab heating and air conditioning and start engine. Run engine on a fast tickover until you are sure that that the coolant temperature is hot and stable, then switch off the engine.

The coolant level should have risen by 12 to 16 mm - depending on temperature - and created some pressure in the expansion tank. Mark this level with a permenant marker. Wearing a glove to protect your hands, slowly release the expansion tank cap and jiggle it about until you can no longer hear any air escaping, hence no pressure. The coolant level will rise in the tank indicating how much air is left in the coolant system. Mark this new level.

My experience is that a rise of level of between 1 and 4 mm is about the best I can hope for, but I do try and get it down to around 2 mm. In theory, a completely purged system should remain at exactly the same level when the pressure is released but maybe old coolant hoses expand slightly under pressure or there is a small amount of air which is impossible to remove.

For me, this test works extremely well and I would expect it to show up any head gasket failure or lack of purging.

[Aethelric]

If you had a small hole in the hose, that would have sucked air into the engine as it cooled resulting in your initial problem. After that, it all points to what Simon says (there a song there somewhere) above. It needs properly bled before you drive it anywhere. Its not hard, but its laborious. If your local garage is not bongo knowledgeable, I'd advise doing it yourself.

Bongobens test looks like a great idea. (I'm going to try it myself) I think the hoses and the header tank itself will expand slightly, but Bens 1-4mm is a great guide. But don't forget that its a test to see how well you have bled the system, if you have not done it well then hot coolant could gush out when you loosed the cap.

Good luck

Dave

[monfluffy1987]

Thanks for your responses everyone! Very quick indeed!

Well the trouble is, I spent a couple of hours bleeding the system by the book! Or so I thought, so I don't hold much confidence in doing it again.

1 think to add though, when bleeding the system, am I right in saying that the only two places to open / disconnect are the bleed pipe under the passenger side and the expansion cap? this is what i managed to decipher from the instructions in bigdaddy's method from the thread. so i tried to stick to it.

Do you have to remove the bottom hose from the radiator at any point? this is something that my dad did thinking he was a bongo expert even though there was no mention of it in the instructions! Would this cause any problems?

Is it worthwhile me continuing to search for small holes etc?

Thanks again!

[Veg_Ian]

You are correct in saying the only two places that should be opened during bleeding are the expansion tank cap and the bleed hose. These are in theory the highest points in the cooling system and air bubbles upwards. Opening the bottom of the rad during this process is likely to introduce more air to the system. So tell your dad he's sacked. For peace of mind I would go through the bleeding process again following the official method or see-saw or BDC methods as published on here. One further thing to note, any restrictions in the rad core could also be causing your overheating problems so if you haven't done so already give it a good backflush.

[monfluffy1987]

Oh this is news to me - what's a back flush? How do I do that?

Also - could a problem with my expansion cap affect the problem (i.e. being too stiff and not opening correctly?)

thanks,

[Veg_Ian]

See Simon's tip further down this forum re backflushing. Essentially what you are attempting to do is dislodge the scale and debris that builds up over time in the narrow pathways through the radiator core. This comes about from being stood and unused for lengths of time and from using poor coolant (ie just water or antifreeze without rust inhibitors) exactlly the conditions that many of our Bongos have been through whilst living in Japan and sat on the side of docks for months on end!

Essentially you need to drain the rad then with bottom and top hoses off and rad cap off force water up through the bottom outlet from a hosepipe, Drain and repeat then fill and bleed as described earlier. You can also get commercial descaler products as well. Never used one but someone else may comment on them and their use later.

[Veg_Ian]

Forgot to add - if in doubt about your rad cap then replace it.

[Simon Jones]

Marc - you've prompted me to post a tip on back flushing that I've been meaning to do for a while:

http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=25140

Basically, it's where you force clean water thru the system from bottom to top to dislodge & wash out all the sediment & goo that builds up, especially in the radiator. It will get any loose bits of rust etc out of the system so it should reduce the chances to getting a blockage in the radiator.

It's something that ought to be done every time the coolant is changed (that's just my opinion, not necessarily what the manual states). However, if you're going to spend £10 on anti-freeze & up to an hour changing/bleeding it, then another 20 or 30 mins won't go amiss.

The general opinion seems to be that the Japanese coolant tends to be more prone to silting up the radiator, which is made worse when the vans can sit unused for many months at the docks.

With regard to the expansion tank cap, it is designed to allow pressure to escape at 1.1 bar. This is also the same as the radiator cap, so I've often wondered why its always the expansion tank that always blows first. The rad one should have a red label & yellow for the tank. There have been instances where either the spring-loaded rubber seal, or the neck of the tank have been damaged which resulted in water being lost at much lower pressure. If the cap does not allow the pressure to be released until after 1.1 bar, then it will find the next weakest point to escape, which will probably be by splitting a hose.

[Simon Jones]

Veg_Ian - you beat me to it on that reply so appologies for the replication of info

[Bob]

Hi Marc and welcome, Discount Trucks, in Newbury know their Bongos.

[Big Rich]

Hi i hope you have better luck than me .....gauge shot up?? STOPPED STRAIGHT AWAY ! popped up seats and TINY pin hole spotted in hose, squirting Very fine jet, so water still going round the system ....fitted new hose! ...... Upshot HEAD BUGGERED UP = FITTED NEW HEAD.... one of my fiesta vans 1800 diesels .. BOILED IT DRY FITTED NEW HOSE NO PROBLEMS AT ALL simply it appears there is no leway at all on a bongo -water + overheated = buggered head.. Just hope you have found it quick enough............. Regards Bigh Rich