Couple of Newbie Techie Questions!

Technical questions and answers about the Mazda Bongo

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joeldrummer79
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Couple of Newbie Techie Questions!

Post by joeldrummer79 » Sun Sep 24, 2017 10:18 pm

Hi Guys

New here, introduced myself on an earlier thread
viewtopic.php?f=1&p=695702#p695695

and looked through loads of threads regarding a few issues I have with my (new to me) Bongo, learnt an awful lot about motoring in general as well as Bongos so was wondering if anyone can help me on a couple of things?

Saw the videos on Coolant bleeding, but is this method removing the old coolant? My header tank is near enough empty (had to put a cable tie through a little slit to left of the tank to find about 2mm of coolant. Don't know what colour or sort of coolant it is so assuming I need to empty it, flush it out before I re fill? I'm having water pump and aux belts replaced as a precaution on Tuesday, (as well as timing belt and full service) I assume the mechanic will flush and re fill? is it normal to flush and refill when the water pump is being changed? Or can I just top it up with a universal coolant that will mix? If so what sort would you recommend? I shall be checking for leaks once water pump is done.

My Bongo is an SGL5 model meaning it is 4WD. I've noted on here that the tyre sizes are different front to back. Checking my alloys that were fitted by previous owner the tyres on them are 215/50/R17 all round...... This doesn't sound good at all being a 4WD. And with the Rear conversion the rear tyres look flat haha. These are really nice wheels, I don't want to have to change them, cos I'm skint haha. Will these wheels and tyres be ok or not?

Oh and I've ordered a passenger door power window switch and wiring from switch to the motor, Is this wiring easy to do? Does it terminate under the glove box, think its a 6 pin plug or something.....

Thanks
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Tony x
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Re: Couple of Newbie Techie Questions!

Post by Tony x » Sun Sep 24, 2017 10:50 pm

Hi. I'll help with the bit I know most about.
The critical thing with the 4WD is having the tyres the same size or, to be completely accurate the same rolling circumference. Your tyres will make the Bongo a tiny bit undergeared but will be fine. When it comes to replacing them you can go for 225 50 17 which will make the gearing stock ( use a 195 70 15 spare if your spare wheel is 15 inch) or (which is what we've done) fit 225 55 17 tyres which make the gearing a little taller but allow more choice for tyres that will make the most of the 4WD such as the excellent Michelin Latitude Cross
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Re: Couple of Newbie Techie Questions!

Post by joeldrummer79 » Sun Sep 24, 2017 10:57 pm

Tony x wrote:Hi. I'll help with the bit I know most about.
The critical thing with the 4WD is having the tyres the same size or, to be completely accurate the same rolling circumference. Your tyres will make the Bongo a tiny bit undergeared but will be fine. When it comes to replacing them you can go for 225 50 17 which will make the gearing stock ( use a 195 70 15 spare if your spare wheel is 15 inch) or (which is what we've done) fit 225 55 17 tyres which make the gearing a little taller but allow more choice for tyres that will make the most of the 4WD such as the excellent Michelin Latitude Cross
Hi Tony

Thanks for this info.... So you're saying that with the wheels and tyres I have, I shouldn't have too much of a problem with the drive train, ie. Potential damage? I read on here somewhere that tyres should be 15" particularly on 4WD, more specifically

FRONT 195/70R15 92SREAR 215/65R15 96S

So I'm OK with the tyres I have as long as I put a 195/70/R15 on the spare?
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Re: Couple of Newbie Techie Questions!

Post by Bob » Sun Sep 24, 2017 11:03 pm

Hi, the mechanic will likely only flush the system if you ask for this to be done. Lots of peeps refuse to pay for work they haven't asked for.

Are you using a Bongo savvy garage? The system must be bled after fitting a new water pump, but they don't all know that.

Same size tyres all round is fine, good advice from Tony. The load rating must be adequate for the weight of the vehicle, min 92 on the front and 96 on the blunt end of a Bongo.

Anything less will invalidate your insurance and is dangerous. :(

The numbers are on your tyres. :wink:
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Re: Couple of Newbie Techie Questions!

Post by joeldrummer79 » Sun Sep 24, 2017 11:40 pm

So it looks like my load rating is 95 V XL all round. This means I will have to change my rear tyres due to the load rating? Is this correct?

My mechanic is just a normal mechanic but he's good. I expect in this case I'm going to have to ask him to flush the system and I pay him extra. Gutted haha. I just want to make sure that the coolant system is tip top and with the header tank pretty much empty I fear there is air in the system. (There's probably a leak somewhere as well but need to have it full before I can find it) ;-)

Funny thing is, I had no obvious heating/cooling problems on my last trip (3 hour drive from Norfolk)
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Re: Couple of Newbie Techie Questions!

Post by Bob » Sun Sep 24, 2017 11:51 pm

Just make sure he understands the VITAL need to bleed the system properly.

We've heard many tales of the world's very best mechanics saying, "Don't tell me my job, I've been doing this for 30 years".

Then we read of the blown head. Just sayin'. :wink:
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Re: Couple of Newbie Techie Questions!

Post by joeldrummer79 » Mon Sep 25, 2017 12:10 am

Good advice Bob, don't worry, I am as keen to have the system totally flushed/bled as anyone. I want to make sure this is done properly.

Out of curiosity and forgive my naivety, I'm new to Bongos so just what IS so different about the coolant system to other vehicles?
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Re: Couple of Newbie Techie Questions!

Post by Bob » Mon Sep 25, 2017 7:03 am

Just the need to bleed it properly after any coolant loss.

Otherwise you get an airlock which causes the head to fail.

Goodness knows why the designer was allowed to get away with it. :roll:
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Re: Couple of Newbie Techie Questions!

Post by mikeonb4c » Mon Sep 25, 2017 9:59 am

Personally i think 95 load rated tyres on 15" wheels should cope fine as long as they're not low profile type tyres. But i'll get shot down for saying that as technically they are below spec for the rear axle and as said there are insurance implications.

I recall my Bongo coming with 17" alloys and 50 depth tyres on with load rating of 92. Side wall cracking was evident, though even there they'd made it to full tread wear end life. I replaced them with 55 depth load rated to 99 all round and have stayed that way since, for a great ride. I have 15" steels which i have used also over the years.
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Re: Couple of Newbie Techie Questions!

Post by joeldrummer79 » Mon Sep 25, 2017 10:07 am

mikeonb4c wrote:Personally i think 95 load rated tyres on 15" wheels should cope fine as long as they're not low profile type tyres. But i'll get shot down for saying that as technically they are below spec for (i think) the rear axle.
Mine are 215/50 R17 95V all round. I could do without changing them as they're pretty much new but I am concerned about the weight over the rear axle... It has a rear conversion and wheels do look pretty flat. That's a point actually, what should the tyre pressure be for this tyre/load and with a rear conversion? I've checked internet but cannot get a definitive answer! :-)
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Re: Couple of Newbie Techie Questions!

Post by mikeonb4c » Mon Sep 25, 2017 11:05 am

joeldrummer79 wrote:
mikeonb4c wrote:Personally i think 95 load rated tyres on 15" wheels should cope fine as long as they're not low profile type tyres. But i'll get shot down for saying that as technically they are below spec for (i think) the rear axle.
Mine are 215/50 R17 95V all round. I could do without changing them as they're pretty much new but I am concerned about the weight over the rear axle... It has a rear conversion and wheels do look pretty flat. That's a point actually, what should the tyre pressure be for this tyre/load and with a rear conversion? I've checked internet but cannot get a definitive answer! :-)
I've read a lot of people (including me though i'm running just a little lower these days) just going for 38-40psi all round. May be a bit on the hard side but should help fuel economy an be ok as long as tyre tread wear looks even. Might be interesting to call your insurance to discuss. Could be they'll allow 95 rated as its almost on spec. Come to that, ought they to be notified about 17" wheels as being aftermarket/non standard? A lot of Bongos have come in from Japan with under-rated tyres. Why?!?
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Re: Couple of Newbie Techie Questions!

Post by Bob » Mon Sep 25, 2017 11:52 am

I've 38 front and 40 rear for a long time.

Seems a good balance. 8)
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Re: Couple of Newbie Techie Questions!

Post by rita » Mon Sep 25, 2017 12:00 pm

The vehicle Manufacturers Designers / Technicians spend shed loads of money and time Developing and safety testing their product.They give the specifications (required by law for that specific vehicle ) the Tyre Rating/Size and Tyre Pressures .

To keep within the LAW it is advisable to adhere to the specifications .But as we all know some people know better than the experts.

Its really up to you what you want to do with theses specifications , as they say you do your bit ,you pay the consequences.

Please Take care

Good Luck.
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Re: Couple of Newbie Techie Questions!

Post by Tony x » Mon Sep 25, 2017 8:00 pm

joeldrummer79 wrote:
Tony x wrote:So I'm OK with the tyres I have as long as I put a 195/70/R15 on the spare?
Hi
No, the 195 70 15 tyre is only suitable for a spare with the 225/50 17 tyres, not the smaller ones you have,
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Re: Couple of Newbie Techie Questions!

Post by mikeonb4c » Mon Sep 25, 2017 8:37 pm

rita wrote:But as we all know some people know better than the experts.
2nd that Rita. From the evidence, it seems that some motor industry fitters seem to know better than the experts too. It baffles me how tyres rated as low as 92 get fitted to a Bongo. Even if they don't know what the figure should be, experience from dealing with other van-like vehicles ought to have resulted in them making a better guess.

The OPs problem is arguably complicated by the wheels being non standard. I don't know enough about the relationship between tyre wall depth, tyre size and load rating to comment but maybe someone (you?) knows. I suspect though that, as with many similar safety related calibrations (speedo calibration, g limits in aircraft etc), the Bongos tyre load rating
requirements probably have a % over-rating that is significantly greater than (96/95)%, which is what led me to make my observation. HOWEVER, it is what the insurers think that is crucial, which is why i suggest the OP call them (and they'll probably say much the same as you) 8)
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