Thermostat problem???

[dp bradford]

Hi Folks,

Just had my Freda overheat

I could hear the coolant boiling and spluttering out of the header tank overflow....

So I stopped. As you do. I could detect no apparent leaks on the hoses or engine, I've checked the oil and it's nice and black (no mayo in there!), so wondered if the thermostat had jammed shut?

Fortunately I was about a quarter of a mile from home, so I added cold water to the header tank (after a suitable time had elapsed to allow me to get the cap off without boiling coolant being thrown everywhere) and headed home.

I've just spent the last hour and a half trying to bleed the system and despite almost an hour of running at various revs the lower radiator hose is still cold. The radiator doesn't appear to be blocked (squeezing the bottom hose with the radiator cap off produces a flood of coolant from the top)

The heaters, front and rear, are blowing nice and hot and the temperature gauge is steady at 11 o'clock.

So, what's the combined wisdom of the group? Thermostat? Or something much worse...

Dave

[mikeonb4c]

Wait and see what the techies say but thermostat would be my first suspect, then maybe water pump (mind you if its pumping water out the bleed hose OK - is it? - then that would seem unlikely) ? Unless the rad. has suddenly suffered a catastrophic blockage? Also seems unlikely nut....

Might as well fit a new Mazda stat anyway as cheap and if the old one is of uncertain age and go from there.

Hopefully all sortable and with no damage

[dp bradford]

...(mind you if its pumping water out the bleed hose OK - is it? - then that would seem unlikely) ? ...

Yes, if I lower the bleed hose to engine height the coolant flows at quite an alarming rate - and it's HOT

Dave

[dp bradford]

Bongo shop is out of stock of genuine thermostats - does anyone know the part number so I can see if a local Mazda dealer can source one? I've been searching and the consensus seems to be that it's not worth bothering with non-genuine / pattern parts for this essential component.... any comments on that - or relevant experience; is it OK for me to buy a non-genuine one from somewhere like BongoBits that appear to have them in stock? Do I need a gasket or is the seal on the thermostat all that's required? I need my Freda to be running!

Dave

[Northern Bongolow]

mazda order these for next day delivery, skipton are good.
part no mkl 0115171a £16 each plus vat

worth every penny. no gasket needed it has a rubber sealing ring on it.

check the port in the top of the stat housing,lye on the ground and shine a torch up into the stat housing,the ring/port should be bright and shinney,if not clean with emery cloth or similar,if you dont the stat will not seal the top port properly when it opens once fitted.

tip remove the bolt that hold the dipstick in place first.

[dp bradford]

Thanks for the info - I'll be straight on it in the morning

Dave

[mister munkey]

You're doing the right thing.

For the uninitiated, from what I've read on recent posts & research here have identified that the Blueprint copies look the same, open at the same temp but don't Go All The Way, so to speak. A fully opening stat will give your engine a better environment to live in. The cheaper copies although apparently work to the same spec, will restrict coolant flow giving rise to future problems sooner rather than later.

[dp bradford]

... The cheaper copies although apparently work to the same spec, will restrict coolant flow giving rise to future problems sooner rather than later.

Thanks - I'd guessed as much - it's really not worth messing about for the sake of a tenner

Just need to hope this will solve the problem! Still, puts me off the road for a couple of days - perhaps I should invoke one of my (so far un-resolved) new years resolutions - and get my push bike out of the shed

Dave

[widdowson2008]

You're doing the right thing.

For the uninitiated, from what I've read on recent posts & research here have identified that the Blueprint copies look the same, open at the same temp but don't Go All The Way, so to speak. A fully opening stat will give your engine a better environment to live in. The cheaper copies although apparently work to the same spec, will restrict coolant flow giving rise to future problems sooner rather than later.

To be absolutely pedantic, not strictly true mister munkey
The Mazda and pattern stats actually do perform exactly the same way. Where they differ is that the Mazda stat has an extra seal on the stem which prevents loss of wax at the extreme upper end of the temperature range.
What happens when wax is lost (and it doesn't take much of a loss for this to happen) is that the stat becomes 'lazy' - ie: it takes a higher temperature for it to respond. Also, at the top end, it may not fully close the bypass, again due to the wax loss.
Got to stress that wax loss will probably only happen if the stat has experienced very high temperatures.
see sketch on 6th entry on post http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=39193

Having said all that, considering what the stat actually does and the price difference between genuine and pattern stats, I personally wouldn't even consider the cheaper version. What say you Ady?

[Northern Bongolow]

i agree with the compatible,or rather the lack of compatibility steve,out of all the tests ive done the gen mazda stat (nearly)always out performs the several other brands i have tested.

my only reservation i have is i have seen 2 old,age unknown gen mazda stats that have been lazy in operation until pan tested to boiling point,once fully opened and allowed to cool,they appear to act like new ones again,outside the system.cant get my thick head round this.

conclusion.change your stat regularly,what ever the make.i personally think that the gen stat is far superior to any others out there,and thats whats going in mine,always.

[widdowson2008]

my only reservation i have is i have seen 2 old,age unknown gen mazda stats that have been lazy in operation until pan tested to boiling point,once fully opened and allowed to cool,they appear to act like new ones again,outside the system.cant get my thick head round this.

I had a brand new Mazda stat for testing from Ian and it did the same - slow to respond on first test but then behaved properly on subsequent tests, suggesting that whatever you put in, pan-test it first to get it moving.
It was suggested a while ago (and sounds reasonable to me) that an old stat would have dried up coolant residue on the stem and needs the initial kick to release it. Not sure on reasoning for a brand new Mazda stat doing this though.
Sometimes wish I had never started looking into the cooling system bits & pieces - resolve one issue and another two spring up in its place

[Northern Bongolow]

keep bashin on steve

[mikeonb4c]

...and remember, a fantastic stat is not a cure all for a system with poor circulation. Similarly, a less effective stat may do a perfectly adequate job for a system that is in otherwise good condition. We have only recently zeroed in on the idea that using a Mazda stat is better, but I suspect many Bongos (mine included) are running around quite happily with a blueprint product in them (its the lack of QA with non Mazda brands that can often be the issue).

[dp bradford]

.... tip remove the bolt that hold the dipstick in place first.

Top Tip, thanks

Did the job this afternoon, in the rain Everything now back to normal

For anyone else contemplating doing this job...

Don't (if at all possible) do the job in the rain. Really not Although, to be fair I did have a fully waterproof Hi Viz boiler suit on, so it wasn't too bad - must have looked a proper charlie though

At the very least, get the vehicle up on ramps - but if you can access a pit or a proper lift then all the better. I did it with the vehicle just standing on my driveway, and it's the last time I'll fall for that one Good grief, there's not a lot of ground clearance - I didn't realise the thermostat housing was so inaccessible - I had to use the long extension bar from my socket set and even then couldn't get quite 'square on' to the two 12mm housing bolts, to get properly square on I'd have had to drop the front prop shaft off! But I managed (with the help of the universal joint in the set). Eventually

The plastic under-tray will be refitted another day - it's one thing dropping it off in the rain, but there's no way I'm going to attempt to refit it until the weather improves!!!

Still, thanks for all the comments and advice - fantastic as usual

Dave (with a bit of a stiff neck!)

[mikeonb4c]

Excellent -glad its sorted