Bongo Fury

Hi Guys. Had an unexpected coolant loss through the expansion tank by the cap being blown off. Luckily it jammed on the rim , so managed to retain it

However am having problems getting fresh coolant back in having followed Haydn's instructions to the letter... and the wife getting some sarcastic comments from friends in the marina as she got the job of raising and lowering the funnel up and down while I did the hard bit sitting revving it up and checking the header tank

Thing is we spent 2 hours doing the cycle as instructed got a luke warm response from the heaters and the bottom radiater hose was still cold when we gave up, locked up, and went down the pub.

Now am thinking maybe the thermostat is faulty, however when I squeezed the bottom pipe Sharon said bubbles appeared in the funnel, so maybe it's not the thermostat? Dunno, but can't figure out why the cap got blown off in the first place.

Can't be the pump at fault as coolant is sucked in when at 2500rpm.

I check the tank regularly so perhaps I did'nt put the cap back firm. When it happened I was only doing 20mph but previously to that had it up to 50mph. I had plenty of spring water at the time and managed to limp home by filling the tank with that.

So can anyone come up with a solution or throw some idea's my way ?

Happy New Year!

John AND Sharon

may be the rad or a pipe is blocked

might be an idea to add rad flush

run it and dump that and try backflush with a hose

would not hurt to change stat

Hi there,

Outsider here but what caused the cap to come off, had it failed or not been put on properly?

Did you car overheat? If so what caused that in the first place. Could maybe the pump have failed or a belt, this would cause no circulation and make bleeding impossible but then you'd get overheating?

Just a thought.

Andy

handyman wrote:
Thing is we spent 2 hours doing the cycle as instructed got a luke warm response from the heaters and the bottom radiater hose was still cold when we gave up, locked up, and went down the pub.

Now am thinking maybe the thermostat is faulty, however when I squeezed the bottom pipe Sharon said bubbles appeared in the funnel, so maybe it's not the thermostat? Dunno, but can't figure out why the cap got blown off in the first place.

John AND Sharon

Hi John,

Two thoughts are:

Could it be that, in this freezing weather, even 2500 revs is not enough to get the stat working - maybe getting the van in somewhere warmer might help
OR
Try taking the stat out, and checking it in a pan of water - a quick and dirty way, but would test it reasonably conclusively. (I believe they open around 84deg, Widdowson88 has posted loads of great stuff on them)

SD

Personally I would try & get it up to temp with the heaters OFF, especially in these temperatures, just flick them on once the temp gauge needle rises to check they're functioning (then turn them off again), otherwise they're bleeding the heat from the system.
Unless the stat has failed open (which apparantly can happen) it doesn't sound like that's at fault (although it's always a good idea to replace with a TESTED new one IMO) as it wouldn't affect how quickly the temp rises, as the stat will only open once the system has got hot enough - the heaters should be hot way before that point.
Good advice give in the previous posts, also make sure you don't leave it without proper coolant concentration in these temperatures.

Thanks for replies.
Including Harry's advice re seperate post.

Bottom rad pipe is flexible and cold not frozen.

Kirsty, I take your point about heater. Which is why I think the stat is at fault because we reached operating temp on bleed and maintained that for some time and still bottom pipe remained cold. I know rad is not blocked as I removed rad cap and squeezed bottom pipe and water gushed from the top of rad.
Theres enough coolant in the top end of system as we left it.

Proof in pudding will be removing stat I suppose.

Anyone know where that is?

No just kidding!!

Regards

John

Good advice above. Out of interest, is the coolant clear looking and/or is there rust staining in the header tank?

On bleeding, I did mine using the workship manual method, not the see saw one, in case you want to try a less hysterical method

Good luck - keep us posted

I remember 'samuel' posting something about having trouble bleeding his after the header cap blew off. He discovered that the seal between tank and cap wasn't sealing, AND he had a leaking hose. The summary of the problem is on THIS LINK and the full version is ON THIS LINK

handyman wrote:Thanks for replies.
Including Harry's advice re seperate post.

Bottom rad pipe is flexible and cold not frozen.

Kirsty, I take your point about heater. Which is why I think the stat is at fault because we reached operating temp on bleed and maintained that for some time and still bottom pipe remained cold. I know rad is not blocked as I removed rad cap and squeezed bottom pipe and water gushed from the top of rad.
Theres enough coolant in the top end of system as we left it.

How do you know you reached "operating temp" ?? your gauge reaches "normal 11 o'clock" position at about 55C (nowhere near "normal" operating temp) it then sits there without movement up to around 110C.
The fact your gauge reaches 11 o'clock means very little....
It will take around 45 mins to get the Stat open (bottom hose hot).....If your stat was NOT opening I would expect you to have overheated before now.

My expansion cap came off after I had topped up the levels - fortunately, my hi-lo alarm screamed so I stopped pretty quickly and no damaged was caused. It took me 2 long weeks to be sure - bleeding the system, reving etc took several hours to be certain there were no air bubbles left & a sniffer test combined with oil & water checks didn't show any problems after 2 weeks of use.

Twas the thermostat that did it.

Thermostat was only opening about 2mm at 82c and at 90c it was still shut. On the outer brass casing of the wax cartridge there were scoring marks where it had jammed. So I put it in a pan and continued to heat and forced it to open fully at boiling point. After that the scoring marks continued right up the brass cartridge.

Anyway after new thermostat was installed I flushed the radiator half a dozen times to get rid of that 'mucky brown stuff',bled the system and with the help of a digital thermometer stuck the probe in the expansion tank and the bottom hose got warm at 83.5c

I used the official Mazda workshop method of bleeding the system rather than the 'funnel' method as it's easier to do on your own and a lot less stressfull than when the wife was playing with the funnel.

So we are back on the road as of this morning and am keeping an eye on levels.

Thanks to the following for advice and to one individual for the 'official Mazda' bleeding method

Wonkanody
Apole
Stilldesperate
Missfixit70
Mikeonb4c
Doone
Haydn Callow
Matt and Joybongling
Aunt trumper

Glad you got it all sorted and hope you've cracked it now.

Andy

apole wrote:and hope you've cracked it now. Andy

Let's hope not