COOLANT LOSS DETECTION KIT

haydn callow · Post by **haydn callow** » Thu May 17, 2007 5:41 pm

Progress is good with the prototype and I have it fitted and it seems to be workin well. However my Bongo has a plain blanking cap on the Radiator rather than a pressure cap which I have on my header tank. This blanking cap is a important part of the alarm system and a pressure cap will not do the job. My questions are ... what good does a pressure cap do on the rad when you have one on the header tank ??? I can only see disadvantages.. if it were to fail you would be loosing coolant and then if you stopped air could be sucked in as things cool down.
The other question is ....how would some of you feel if you were asked to bin or modify your existing pressure rad cap and fit a plain one in order to have a coolant loss alarm.
A point to note. If you have a rad with metal rather than plastic end caps ( top/bottom) the alarm would not be suitable in it's present form.
My bongo came with a plain rad cap and a 1.1 bar pressure cap on the header. (it's fine)
If your rad has a outlet tube below the cap ,this would have to be blanked off ..easy to do.
I would be interested in any feedback and we are looking for a volunteer to try out the Mk2 alarm system (free) and report in confidance. This would entail fitting the kit and testing it under working conditions. This would involve draining hot coolant under pressure. Topping up and bleeding. I've done this about 10 times in the last couple of weeks and it's no longer a daunting prospect.

francophile1947 · Post by **francophile1947** » Thu May 17, 2007 6:13 pm

The Bongo is the only vehicle I've had with 2 pressure caps - all others have had one on the header tank only, so I would have no problem changing over. I'm no good for your volunteer though, I don't use my Bongo enough to give it a good, and quick, test.

Bonza · Post by **Bonza** » Thu May 17, 2007 6:59 pm

This was just the conversation I had with the guy at BongoBits.
The rad cap has the same part no. as the expansion cap but other numbers are quoted as well. They are not identical.
The rad cap is plain with no pressure relief and the expansion tank cap has a pressure relief valve.
Price without the relief valve £21, with relief valve £8 or so. thus everyone probably chooses the cheaper option and uses a pressure cap all round.

Love to help Haydn but I'm recovering from a broken back (fractured vertebrae last year) so work on the Bongo is fairly limited as I get better.

Bonza

haydn callow · Post by **haydn callow** » Thu May 17, 2007 7:37 pm

Bonza ...yes & no,
I have been in touch with Bellhill garage.. VERY helpful... They said" all the bongos he can remember and all the ones outside being broken down have 2 pressure relief caps fitted and all have Jap labels on. One red and the other yellow. Both say 1.1 bar and look the same and are interchangeable. I forget which colour is supposed to go on which but there is a correct way. Dispite this they are often mixed up. If two pressure caps are fitted it would make sense if the header tank one was the lower pressure one. You wouldn't want the rad one to blow first. But again I ASK.. what is the point of having one on the rad? Surely a blanking cap would be better. As I see it the only reason for having a cap on the rad at all is to help when filling/bleeding the system.

haydn callow · Post by **haydn callow** » Thu May 17, 2007 7:40 pm

Regarding the cost. The pressure cap ..approx £7 is ( I think ) a "pattern" cap and the plain cap £24 is origanal mazda

trevd01 · Post by **trevd01** » Thu May 17, 2007 9:19 pm

haydn callow wrote: I forget which colour is supposed to go on which but there is a correct way.

Just looked at ours (I didnt even know there was a radiator cap under the air intake).

Red on the radiator, yellow on the expansion bottle.
And the radiator has no overflow/outlet.

Now I can't swear that that is the correct way round, but we do have a full Japanese service history with our Bongo, and everything looks original.

Bonza · Post by **Bonza** » Thu May 17, 2007 9:23 pm

BongoBits had a s/h radiator and the cap was a non pressure relief cap.

I think thats the correct one for the rad.

Bonz

haydn callow · Post by **haydn callow** » Thu May 17, 2007 9:24 pm

Trevd01... is the one on the radiator a pressure cap ..i.e has it a spring under the cap??

haydn callow · Post by **haydn callow** » Thu May 17, 2007 9:25 pm

Bonza...so do I

trevd01 · Post by **trevd01** » Thu May 17, 2007 9:30 pm

haydn callow wrote:Trevd01... is the one on the radiator a pressure cap ..i.e has it a spring under the cap??

I'll look tomorrow - its a bit dark now.

trevd01 · Post by **trevd01** » Fri May 18, 2007 6:22 pm

haydn callow wrote:Trevd01... is the one on the radiator a pressure cap ..i.e has it a spring under the cap??

OK here we go.

Yes they are both pressure caps.

But the wording on them is subtly different

So the red one clearly says 'Radiator Use Only'. Other than that they look identical.

Oh yes - the other thing, the top of the radiator appears to be made of plastic???

Thanks for making me look in better light, some bare metal where the air intake has been rubbing on the bodywork, with some light rust, which I will now touch up with some waxoil.

haydn callow · Post by **haydn callow** » Sat May 19, 2007 12:18 pm

As I see it... if you have a pressure cap on your Raditator and your radiator doe's NOT have a coolant expansion outlet spigot in the neck of the radiator it serves no purpose at all othe than to seal the filler. If you look at a pressure cap it has two seals in it. One which is on the bottom of the spring and seals at 1.1 bar at the bottom of the rad neck. The other seal is directly under the cap and seals the top of the rad filler. This top seal is not pressure regulated and will never allow coolant out the top. The only reason as I see for fitting a pressure cap to a Rad which has no expansion outlet under the cap is the cost of a plain cap(£21). If anyone out there thinks different please let me know. The coolant loss alarm I am wotking on ,does ,at the moment in it's present form needs to have a plain cap fitted. I have modified a pressure cap to do the job we require but it is no longer a pressure cap. It works fine on my Bongo but I did have a plain cap fitted to start with

dandywarhol · Post by **dandywarhol** » Mon May 21, 2007 10:38 pm

I don't understand why the radiator has a pressure cap either but it seems that the majority of Bongos have a red pressure cap on the radiator (marked radiator only) and a yellow one on the header tank in the left wing area.

Bonza · Post by **Bonza** » Tue May 22, 2007 8:54 am

I like to think the answer is because as Haydn says that the red pressure cap on the rad is a "pattern" one and cheaper than a non pressure Mazda cap.

But this means that lots of Bongo had their caps replaced to pressure caps (cheaper) at some time does it. Cant believe that. UNLESS this was an effort to control overheating etc or maybe a cheaper alternative on the production line. I'll bet someone at Mazda realised that the non pressure cap was more expensive than the pressure cap and substituted it or the other way round maybe!

But, the rad pressure cap clearly says "FOR RADIATOR USE ONLY". Its the same cap as the expansion tank in function surely, isn't it?

Bonza

trevd01 · Post by **trevd01** » Tue May 22, 2007 2:40 pm

I've just got my son's '94 Honda Accord out of storage - (satrted first turn of the key after 9 months BTW). Looked under the bonnet for the first time in a long while.

That has no expansion tank, just an overflow on the radiator, and it has an identical red pressure cap (same Japanese, English and French wording), as the one on the radiator of our Bongo.