Overheating/coolant boiling after coolant change and bleed

Technical questions and answers about the Mazda Bongo

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mikexgough
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Re: Overheating/coolant boiling after coolant change and bleed

Post by mikexgough » Mon Aug 01, 2016 9:38 pm

Coolants.... Chemistry is important with Bongo's and Jap vehicles... the closest to the Multi colour coolants which come across from Japan chemistry wise is the G12+ Red/Pink OAT - Comma, Car Plan or Triple QX which are available premixed as well as concentrated.
Steer clear of Blue/Green coolants unless they are Mazda O.E which are OAT not like in the UK where they are G11 coolants and do not play well in the playground and to be honest the root cause of many Bongo Head failures and overheating.
The 2 don't mix well but using G12+ in G11 is a slow process to clog and gel.

Prestone Yellow... this is now getting widely available and to be honest is not a bad coolant, one I would only suggest using if you are unsure what coolant you have for a short term basis, however...I guess on a fresh fill it could be used, but I'm concerned a little about any silicates,borates or phosphates, even trace elements of it, but that is my opinion and I guess in real terms it's not as bad as putting in UK Blue which is riddled with them.
At the end of the day it is your Bongo and yer pays yer money and takes your choice.

Now....as always, flush the system well and back flush and when filling do it slowly, as already been suggested squeeze all the pipes and when you do fill.....make sure fresh coolant flows out of the bleed vent hose (if you get some burps of bubbles all well and good) In effect you are bleeding out as much air from the coolant before the engine starts...in effect if you do the above process then all the air left should be in the bottom hose/thermostat area ready to shift when the 'stat opens after the cooling bypass circuit has done it's job.....
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Northern Bongolow
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Re: Overheating/coolant boiling after coolant change and bleed

Post by Northern Bongolow » Tue Aug 02, 2016 9:36 pm

thats the best post thats been on here for yonks, in regard to the oat chemistry needed for a bongo present in red coolant and the reason for bleeding in a slow deliberate manner.

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Re: Overheating/coolant boiling after coolant change and bleed

Post by stuc » Wed Aug 03, 2016 11:43 am

Has anyone suggested a new expansion tank cap. I know mine was fine until it started pushing coolant out the header and it was just a simple cap change.
The cap wasn't holding pressure so not allowing the coolant to raise it's boiling point so possibly showing overheating symptoms earlier.
I may be way off here but worth trying for price of a new cap. Mazda genuine parts are cheap enough 1.1 bar
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Re: Overheating/coolant boiling after coolant change and bleed

Post by Long » Wed Aug 03, 2016 3:25 pm

Hi,

i did try switching the cap already, it was not the faulty cap. I will flush the system backwards and also do a vacuum fill. the coolant i will get is the prestone yellow. it contains no scillates.
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Re: Overheating/coolant boiling after coolant change and bleed

Post by Long » Wed Aug 03, 2016 3:27 pm

I was thinking of using a water wetter coolant additive. it lowers surface tension of the water, and it is anti foaming. and suggestions?

is this something useful?
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Re: Overheating/coolant boiling after coolant change and bleed

Post by Bongolia » Wed Aug 03, 2016 3:52 pm

To help flush it or as an after flush additive do you mean?
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Re: Overheating/coolant boiling after coolant change and bleed

Post by Long » Wed Aug 03, 2016 4:17 pm

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Re: Overheating/coolant boiling after coolant change and bleed

Post by Bongolia » Wed Aug 03, 2016 4:53 pm

Personally, as long as you are using a good quality A/Freeze I wouldn't bother.
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Re: Overheating/coolant boiling after coolant change and bleed

Post by Long » Mon Aug 08, 2016 2:41 pm

Hi everyone,

i completed my flush and vacuum fill this weekend, it worked and the system sucked all the coolant in with no problems. However, i did leave the vacuum on the system a bit longer about 15 minutes. Now the coolant is not flowing into the radiator. when the engine is warm both top and bottom hoses are cool. Could this be caused by a collapsed hose somewhere that stayed collapsed from the vacuum? can i find it and just un-collapse it?

could it be the thermostat? the thermostat was working with no problems before this vacuum fill.

thanks.
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Re: Overheating/coolant boiling after coolant change and bleed

Post by Northern Bongolow » Mon Aug 08, 2016 9:13 pm

it will be an airlock in the top hose pipe to the rad, this pipe leaves the head with coolant very hot but it WILL NOT push air down hill to the horizontal pipe over the axle then up to the top of the rad.

this is why i never use a vac fill method on a bongo, the system has several routes to vac fill, and coolant will always fill the easy route and not always purge all the air out, even if it does a fairly good job, how do you know, the only way to test is to run or drive it, possibly killing it in the process as many garages have done. this is the reason for the often criticised seesaw method shown on youtube.
at this point i must confess to being biased as my wife filmed it on my bongo. :)
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Re: Overheating/coolant boiling after coolant change and bleed

Post by Long » Mon Aug 08, 2016 9:35 pm

Hi,

thanks for letting me know. how would you suggest i fix this problem? do i need to re-bleed it again with the see-saw method?

thanks
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Re: Overheating/coolant boiling after coolant change and bleed

Post by Northern Bongolow » Tue Aug 09, 2016 10:09 pm

give me a ring, i will pm you my number, but the short answer is yes.

all bongos bleed differently, ive bled more than 30 different ones, some need special care, some do it quick, some slowly. ive had em where you need to loosen clips to bleed the front heater to let the air out, and crack the top hose and back fill it from the top.
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Re: Overheating/coolant boiling after coolant change and bleed

Post by Lordward » Thu Aug 18, 2016 11:04 am

Hello,

We are having exact same issues with our bongo as this thread. Could you give me an update on your difficulties, did you solve it, what else did you try, and was it the dreaded head?
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Re: Overheating/coolant boiling after coolant change and bleed

Post by BongoBongo123 » Thu Aug 18, 2016 2:41 pm

Northern Bongolow wrote:give me a ring, i will pm you my number, but the short answer is yes.

all bongos bleed differently, ive bled more than 30 different ones, some need special care, some do it quick, some slowly. ive had em where you need to loosen clips to bleed the front heater to let the air out, and crack the top hose and back fill it from the top.
That is good knowledge Northern B, but frankly scary for existing and potential owners. The cooling system is a thorn in the side of Bongo ownership. Especially those who do not have the fairly deep technical knowledge of doing the job correctly and knowing all the idiosyncrasies of the specific Bongo cooling system.
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Re: Overheating/coolant boiling after coolant change and bleed

Post by Long » Fri Aug 19, 2016 9:45 pm

Hi,

no the problem is not solved yet. even with vacuum fill it did not solve the problem. i am going to try meticulously bleeding it again this weekend and update on results.

if you find a way to solve the problem please let me know.

thanks