Coolant level dropping

[bikemunky]

Hi all,

I'm sure there is an answer on here to my problem, but after hours of trawling I can't find one.

I'm losing coolant from somewhere, the level in the header tank drops over time, and I have to top up every couple of weeks or so. I had another overheat issue tonight,the needle went rapidly into the red so I pulled up, waited for it to cool down and topped her up. She runs fine again and the needle sits where it should. This has happened a couple of times over the last 6 months.

Thing is I can't see any visible leak anywhere. I have been underneath, under the seats, everywhere, but I can't see anything. I changed the coolant at the end of August, thinking there may have been a blockage somewhere and it has run fine until today, so I haven't fixed it obviously.

I had notice before I changed the coolant that there appeared to be a rusty coloured leak from around one of the hoses on the header tank, the rusty water has stained the inside of the wheel arch where it has run down. The tank itself is now opaque due to age and you have to take the cap off to check the levels.

Do these tanks fail eventually? And if so can I get another off here? Is so, how much are they? Does anyone have any experience of a busted header tank?

I have checked all the pipework, and inspected each pipe when I changed the coolant, they all looked good, but the one on the header tank was stained with a rusty coloured deposit around the neck of where it atttaches to the tank. There is no visible leak,but could the water be forced out of a whole here under pressure?

[mister munkey]

Chances are there a a few jubilee clips that just need a quarter twst up every few months.

have a good rummage around with a screwdriver & give a tweak to all you find.

I suffer that.

[M 80NGO]

It could be summat simples like a faulty Header tank cap, small pinhole in the radiator thats evaporating the water off before it drips off the radiator or summat major like head gasket, if you have a local garage that you trust get them to do a coolant gas test to eliminate the head gasket issue but get them to do the test for half an hour as my head gasket had a tiny leak that took about that sort of time to slowly turn the blue liquid a yellowy shade.

Keep us posted

[g8dhe]

Splits in the Header tanks are becoming more common see http://www.igmaynard.co.uk/bongo/forum/ ... 93#p504593

[Northern Bongolow]

get your local garage to do a system pressure test,(not a vac test).inflate the system to about a bar and have a good look round the entire system.
usual candidate for a hard to spot leak is the water pump. it has 2 leak off points in the casting, one is viewable from the passy side behind the belts, its in the quarter past position if viewing from the front, the second is more difficult to spot when leaking, its at the 6 oclock position and very well hidden, if it leaks here it is usually evaporated off so not detected, a dentist mirror is a good idea.
the brown staining is usually associated with boiling.
check or replace the expansion tank cap, and remove the tank and check the underside as geoff says.
check the video's on youtube on how to bleed a mazda bongo, as topping up and not bleeding when its very low is the worst thing you can do. if the bongo will not bleed up as shown in the video's then its likely to have done the head.

good luck.

[mikexgough]

Splits in the Header tanks are becoming more common see http://www.igmaynard.co.uk/bongo/forum/ ... 93#p504593

It doesn't seem all that common when applied to the amount of Bongo's on UK roads, percentage wide and from "known" cass..... It's all subjective per vehicle and "could" be a possible problem area if a leak is needed to be found after the usual suspects have been exhausted..... in all my years of working on older vehicles....of all makes ....I have never changed a header tank yet due to leaking....only for aesthetic reasons..... to make it look pretty...or more like fresh from factory

[B*Witched Blingo]

I agree with you Mike regarding numbers on UK roads etc but, it is another area that perhaps should be looked at in the event of an unexplained leak.

My father made a suggestion years ago when an old car I had developed a raining in problem. He found that simply using talc (baby powder) in the suspected area would leave a trail to the source or problem. Would it be an idea to use this method under the bongo (if dry) leave it parked up over night and check the following day?

[mister munkey]

Best to remove the undertray first I s'pose . . . . .

[mikexgough]

a Bongo group buddy in Japan - Kz-p changed his tank......as was discoloured not because it was leaking...... and it hasn't overheated .......

[bikemunky]

Hey guys,

Been over the bongo again in the full light and dry. There was a small patch of water on the passy side. With the bonnet up and looking down it is where water would run down the inside of the arch/bulkhead if the header was leaking. From underneath there is evidence of wet (antifreeze) that has collected in areas underneath and there are drips down here. Also there is a rubber flap that protects the engine bay from road spray and this too is dripping with antifreeze.

I have removed the tank and cleaned it down (how flipping good are wet wipes!!!?). Before I took the tank off the smaller of the two pipes was wet at the union and there was brown staining here which suggests there may have been a leak here? Anyhoo, on removing the tank and cleaning it there appears to be a small crack that goes 2/3rds of the way around the connection. It starts below the sprue line or manufacturing joint of the top and bottom halves of the tank, over the top and down the other side. Even after cleaning this "crack" remains dirty and looks like a crack so I don't think I'm confusing it with part of the manufacturing process.

I have tried to flex it to see if it opens but it doesn't budge, but like I say it was wet when I took the pipe off (the tank was empty by the way, so no, not leakage from the tank. The missus reckons she can feel it with her finger nail too!

I drove her from Leicester to Tenby some 250 miles the other week and she lost a small amount which I topped up prior to driving home.

I have since driven back and done some local short trips around 300 ish miles but I haven't checked the water and guess what she boiled over, I feel beacuse of a low coolant level and because air is being drawn in somewhere. I have also notice in the mornings, especially now it is cooler that I get a small amount of steaming up on the bottom of the left hand side of the windscreen which I didn't pay any mind, but now on thinking about it is where the header tank is situated.

I have checked everywhere else, all the hoses are sound with no signs of moisture, the rad seems fine with no sign of leakage and the undertray is dry, apart from all that gunky oil you get in there after a rocker cover gasket leak.

What I need to know is, would this hairline crack be enough to empty the tank over a period of time under the pressure it is subjected too with daily use?

[g8dhe]

Very difficult to comment, but it certainly doesn't sound like a perfect tank! If its not actually leaking from the crack yet, the question is how long before it does ? Are you able to get a photo of the tank and crack up I wonder ? (Details for posting pictures here http://www.igmaynard.co.uk/bongo/forum/ ... =42&t=9285 )

[bikemunky]

I'll try to get a pick on here. Beause of the size of the crack, I'm not sure it will show up, it really is that small, but if it is enough for there to be moisture present after use, then surely it is enough for water or steam to be forced out of a pressurised system. However, I'm not a mechanic, not particularly handy under the bonnet, and skint as a church mouse.

[mikexgough]

The small outlet pipe from the tank is sleeved, obviously Mazda put some thought into the construction as the smaller pipe would be weaker......and probably why you can't budge it to flex and show a proper "crack"... I guess,and without handling the tank I can't fully comment....it depends on if the tank pipes have been forced at some stage in the past to allow a crack in that outlet pipe... and a very slight weep and we all know how much coolant can show from a small leak......One thing for you..... of the 2 tanks I have here none have that problem

Spookily,Header Tanks and manufacturing "cracks" were discussed today and moulding techniques and the imperfections that can come about with moulding and how many don't affect the performance of the end products, whatever it is

[mister munkey]

I get a small amount of steaming up on the bottom of the left hand side of the windscreen which I didn't pay any mind, but now on thinking about it is where the header tank is situated.

Thats also where the front heater matrix is, have you had a look around there yet?

[haydn callow]

I have removed the tank and cleaned it down (how flipping good are wet wipes!!!?). Before I took the tank off the smaller of the two pipes was wet at the union and there was brown staining here which suggests there may have been a leak here? Anyhoo, on removing the tank and cleaning it there appears to be a small crack that goes 2/3rds of the way around the connection. It starts below the sprue line or manufacturing joint of the top and bottom halves of the tank, over the top and down the other side. Even after cleaning this "crack" remains dirty and looks like a crack so I don't think I'm confusing it with part of the manufacturing process.

After removing and checking your tank...did you bleed the system correctly..

I would say most "old" tanks will be seen to have the start of cracks underneath (not all the way through but defo visable) how many peeps have seen the underside of their tanks.....I know of 6 that have cracked through and leaked......search the topics and see the photo's