Dude, where's my bleed hose?

[bongojoe]

Had a burst pipe and lost all my coolant. Patched up pipe and was trying to refill system with water to drive a couple of miles to my garage to get it all looked at properly but couldn't find the coolant bleed pipe referred to in all the instructional videos and posts. Am I being daft?

My head was replaced a few years ago after a full meltdown, and I have read a post on here about a different style of head that doesn't include a connection for the bleed pipe. Could this be the case or am I missing something obvious? Here's a pic of the passenger side of the engine, where I believe it should be:



If I don't have one, how would I bleed the coolant system? It has been done by my garage at least once since the engine rebuild.

[g8dhe]

Yes when they replaced the engine they didn't move the three-way across just used the two way fitted, I believe a common answer is to cut into the hose going to the Turbo and add a "T piece and length of hose as the bleed hose.

[bongojoe]

Thanks Geoff.

Presumably the turbo hose is the one going off to the right with the heat shielding?

Is there a reliable method to bleed in the absence of a bleed hose?

[g8dhe]

Yes the one running to the right.
Best to vacuum fill the system even if you have a bleed hose!

[Lemner]

Hello BongoJoe,
A 3 way pipe fitting is another option to replace your existing 2 way one. The 3rd outlet goes to the new bleed pipe.

However another option is to fit a header tank from a 2l petrol (which I think is standard) if you can get one, they have another inlet at the top. Geoff- please correct me if this is wrong Sir.

If you run a pipe from the 3rd outlet to the top hose connection on the header tank the system will mostly self bleed the air out.
You still have to get the engine up to 82c to open the thermostat before the air and coolant will start moving fully.

Another more expensive option is to fit an auxiliary electronic water pump, (my Freda already had the 2l petrol header tank) this is the path I chose and I don't regret it. See my earlier post-
https://igmaynard.co.uk/bongo/forum/vie ... hp?t=78512

With the tiny toggle valve on the thermostat removed, coolant can flow regardless of whether the thermostat is open or closed, albeit slowly.
This makes bleeding the air out a very easy job (with the non standard header tank), you don't need a pipe and funnel. Another huge advantage with an EWP system is that you can decide the temperature your engine runs at and switch the fans on at a lower temperature than the ECU normally would.
There's an argument that diesels need to run hot in order to achieve their optimum fuel efficiency. I can only agree with this (as advised by a mechanic friend of mine) but the relative cost of a few lower miles per gallon verses a replacement cylinder head or gasket is small change in my opinion. I've had both go wrong on my Freda, first the head cracked- then replaced, and a few years later the gasket failed.
All of the coolant issues I have experienced can be attributed to bad design- sorry if this offends, but back in the day Mazda should have looked more closely at the impeller size and the volume of coolant in the system. When the engine is ticking over with no airflow they get very hot. The ECU starts the fans on a diesel at 96c at low speed, and full fans at 108c. Its no wonder things go very wrong so quickly. The smallest amount of sediment restricting coolant flow will magnify problems greatly.
After fitting a Davies Craig EWP system in my Freda, the coolant temperature has never exceed 98c, even when climbing an endless hill in France in 34c summer temperatures.

Trust me Gents, this is the way forward. Its expensive though.

Any questions are most welcome.

[g8dhe]

All the tanks I've seen or heard of have the Third inlet but its blocked off, the spout is there so if you want to make use of it, drill out the plastic and attach any extra hose.

However be aware that Mazda over all the years of production did NOT fit the extra pipe on anything other than the 2l engine, they knew something we don't! You don't complicate a production line with extra parts and the designs with extra hoses unless they have a distinct purpose. Mazda appear to have had a good reason to have different tanks and extra hoses for just the 2l not the diesel or the V6 and complicated the production line - they must have had good reason!

[bongojoe]

After my initial post above, I managed to successfully refill the coolant and bleed the system by raising the front end on a ramp. It took ages but got there in the end and have been driving around without any problems.

However I have now bought a three-way piece and bleed pipe, with the intention of replacing the two-way one to make future bleeding a lot easier.

I had assumed the piece would be threaded, and would simply screw in in place of the one currently there. But of course it's not and I'm not at all sure how it attaches to the engine block.

Before I go and try to replace the old one, can anyone let me know how it works and whether this is a job a (reasonably) competent DIY-er should attempt?

Thanks!

[g8dhe]

I think this has been discussed before but basically force fitted. See here for one method https://www.igmaynard.co.uk/bongo/forum ... 36#p402536

[bongojoe]

Thanks Geoff. Think I’ll save that job for a rainy day.