Can I Remove Thermostat?

[stevejt]

Just had two new tyres fitted ready for long trip tomorrow, but on the way home only 2 miles the bongo overheated - first time. I've checked all the hoses no leaks, no cream in oil. A lot of water lost out of header tank relief, engine cooling fan was on.

I suspect a sticking thermostat, as allowed to cool down and topped up water and now engine appears to be running as normal.

Could I remove the thermostat temporarily just for this ~ 800 mile trip and fit a genuine one later. Is there any reason why I should not do this?

Any help, much appreciated, as I have a very glum looking mrs downstairs.

Cheers,
Steve.

[haydn callow]

I think NO is the answer....if you lost water (coolant) and then just refilled the tank, chances are you have now got air trapped in there.
I would not remove the thermostat unless you put a new "Mazda" one in to replace.

You must get the system bled properly...see many topics on here and the new Vidio (go to webshop below for vidio links.

[missfixit70]

Take the stat out & pan test it, it should open & 82-85 degrees & have at least 8.5mm of lift at 95 degrees. if it doesn't open fully it doesn't close the top recirc port & force the coolant around the rad. Also check its Jiggle pin is in place, I just had a brand new Mazda one that lost it's jiggle pin after 40 miles & it made a big difference, was trying to overheat due to the thin stream of cold coolant telling the stat to shut when it shoulda been open.
I would not run it without the stat for an 800 mile round trip as it won't control the temp properly, & you could well end up with a diastrous overheat, if you haven't had that already
Have you modified the temp gauge or got any temperature sensors, low coolant alarms or anything to help tell you what's going on? the standard gaufge is dumbed down so it is already overheating by the time it moves.
Get it bled properly, as Haydn said, video now available to help as well as the factsheets, but I'd be looking at what's already happened & why - especially if it's chucked out of the header, could well be pressurising system due to head/gasket leak, TBH bongos rarely seem to give the margarine oil symptoms. Mine was pressurising for weeks without any other signs other than a a slight coolant loss, it can be very difficult to diagnose. once it's bled, & the stat checked and/or replaced, if the hoses are feeling pressurised after a run, chances are you've got big issues I'm afraid.

[stevejt]

Thanks both for your advice, much appreciated. I'm hoping that a closed thermostat will cause the rad to overheat and bubble coolant out of the header.

Just been watching the excellent videos, will aim to try and change the thermostat if I can get a genuine one on a Sat morning. Looks like the nuts are not the easiest to undo. Hope it's not the head gasket.

Cheers,
Steve.

[missfixit70]

Closed stat will cause the engine to overheat I'm afraid, these threads may help you to understand the sytem (or not )
http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=35902
http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=36433
Worth trying to pressure test the system http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=38823 to see if there are any obvious leaks that led to the overheat? You didn't say if you have a low coolant alarm or anything that warned you of a problem?
Stat can be done from above using a long extension & reaching underneath, 12mm bolts I think & undo the 10mm bolt holding the top of the dipstick in place so it can be moved out of the way. It is easier to get to if you take off the bottom tray if you've got one in situ. Make sure the top sealing face inside the stat is clean so the top disc can seal against it.

[stevejt]

Done some more investigating after watching the videos and found the radiator weeping at the top seal, looks like this may have been happening for a while as some crusties are evident along the length (largest weep is on drivers side end). The rad seems to have what looks like some foam attached to the top that is perished, not sure what use that is for. The bottom rad hose also feels easy to squeeze, possibly a sign of missing coolant?

I'm thinking if I have to change the rad and stat, I may as well add a new water pump in for good measure. I don't have any temp alarms fitted, one of those jobs I was getting around to.

I'm guessing genuine rad / pump also best option, for any chance of going on the road tomorrow.

[missfixit70]

I'd say you ain't going anywhere tomorrow TBH, you'll be lucky to source that lot on a saturday. I got my rad & waterpump from JAS - http://www.japautosolutions.com/acatalo ... BONGO.html -not genuine but good quality. If you can afford & source proper Mazda it's usually preferable though.
Not sure about the "foam stuff" in the rad (Hate to say it but it could be a sign that someone has used rad seal type stuff in there in the past), but it's a common issue for them to fail along the seam, some have had success crimping the metal tags back over the plastic header part for a get you home, but definitely sounds like it's best to replace before going anywhere. Check the state of all the hoses while you're at it too.

[haydn callow]

I think the foam in question is the strip that runs along the front of the "front" rad A/C.
Mines crumbling away as well

[missfixit70]

Sounds like a more hopeful theory

[stevejt]

I'd say you ain't going anywhere tomorrow TBH, you'll be lucky to source that lot on a saturday. I got my rad & waterpump from JAS - http://www.japautosolutions.com/acatalo ... BONGO.html -not genuine but good quality. If you can afford & source proper Mazda it's usually preferable though.
Not sure about the "foam stuff" in the rad (Hate to say it but it could be a sign that someone has used rad seal type stuff in there in the past), but it's a common issue for them to fail along the seam, some have had success crimping the metal tags back over the plastic header part for a get you home, but definitely sounds like it's best to replace before going anywhere. Check the state of all the hoses while you're at it too.

Well, I was not lucky, so trip cancelled. Parts now on order from JAS. You mentioned that some have had success with bending the metal tags over the plastic header - mine already were. Although the hoses all look good, I'm tempted to replace anyway for having the system apart. The bottom rad hose is easy to squeeze, so it may have lost its rigidity.

Any thoughts on the ebay samco lookalikes or the ava 5 hose set, versus genuine.

[missfixit70]

If you want to fit silicon hoses, the issue seems to be with fitting the right clamps. I've just replaced all my silicon hoses & jubilee clamps for genuine hose & genuine spring clams after 8 - 10 months of weeps & leaks from the hose connections, finally ended up having to get the head replaced. Personally I would only recommend genuine from my experiences, but others may say different.
Haydn Callow is hopefully obtaining a supply of Norma constant pressure hose clamps to fit silicon hoses that may help with their issues?
Bear in mind there are 17 hose in all on the cooling/heating system

Complete list of hoses

Main cooling system - http://www.lushprojects.com/bongopartsm ... mgno=.html

15-261 - bypass/recirc into top of thermostat
15-381 - bleed hose
15-186 - top hose/engine outlet to large metal pipe drivers side
15-183 - Large metal pipe drivers side to top of rad (inlet)
15-184 - bottom of rad/outlet passenger side to large metal pipe passy side
15-185 - passy side large metal pipe to bottom of thermostat
15-227 - top of rad to header/expansion tank
15-188 - expansion/header tank to heater return pipe

Most of front & rear heater system - http://www.lushprojects.com/bongopartsm ... mgno=.html

61-211 - drivers side heater pipe to front heater matrix
61-212 - front heater matrix to heater return pipe
61-214 - heater return pipe to thermostat
61-213 - outlet over starter on engine, drivers side to heater pipe
61-211A - drivers side heater supply pipe to rear heater matrix

Rear heater return - http://www.lushprojects.com/bongopartsm ... mgno=.html

61-212C - rear heater matrix to return pipe behind engine

Another rear heater return - http://www.lushprojects.com/bongopartsm ... 1of02.html

61-213A - rear heater return pipe connector behind turbo under passy seat

Two turbo cooling hoses - http://www.lushprojects.com/bongopartsm ... mgno=.html

13-539A &
13-546 - turbo suppply & return hoses

If you want the part no's click on the index on he left of the drawing no's

Most commmon failures seem to be the top hose out of the engine on drivers side that goes forward towards rad, heater outlet over starter that goes down to the metal pipe T piece, the heater return under the passener seat that feeds into the stat from the metal pipe & the bleed hose. Check them all thoroughly though.

[stevejt]

Spent all day reading about cooling issues and trying to make my mind up if I need to do anything else besides RAD, PUMP and STAT.

I'm leaning towards taking the head off and replacing the gaskets as a belt and braces exercise, along with the main 5 hoses as recommended by ava. Which would also lead me to a cam belt change as it would be all apart (needs doing within next year).

I'm wrestling with the outlay / time investment, changing just what I've got on order and seeing how it goes or changing the gaskets as well. I have some rocker / head gasket oil weeps mainly on the drivers side (EGR blanking plates coming).

After so much reading I guess the decision comes down to this..

Failed head gaskets can cause cooling issues before a head needs replacing, cooking a head can cause it to crack, weeping gaskets could be a sign of deterioration, does one episode of overheating nearly always lead to head / gasket replacement, how many overheating examples have actually been rectified without changing head / gaskets, would a weeping radiator / stuck thermostat combine to cause expansion tank boil over without affecting head or gaskets, does overheated coolant deteriorate gaskets much quicker, cracked heads probably due to hot or cold spots caused by weeping / failed gaskets.

Taking all that into consideration, provided I've not misunderstood, the obvious path would be to change the gaskets and inspect the head at the same time.

I also noticed that the rubber seal on the expansion tank cap is perished around the edges. Is this cap supposed to provide header tank presuure or is it mainly there to allow top up?

[missfixit70]

Sounds like you need to replace the expansion cap, it needs to seal to maintain pressure, the seal is on the bottom seal rather than the top - could be that simple
Sounds like you're thinking along the right lines, but, how are you going to inspect the head? Mine was replaced (system kept pressurising & coolant loss), the old one looks fine but it was leaking into cylinder no2, plus you'd have to replace all the stretch bolts etc. It seems that not many heads survive any overheating episodes in the long term, or being taken off & put back on (stresses dues to loosening & tightening), even if they pressure test ok, there seems to be a good chance it'll still be leaking or will start to within a short space of time.

[stevejt]

Sounds like you need to replace the expansion cap, it needs to seal to maintain pressure, the seal is on the bottom seal rather than the top - could be that simple
Sounds like you're thinking along the right lines, but, how are you going to inspect the head? Mine was replaced (system kept pressurising & coolant loss), the old one looks fine but it was leaking into cylinder no2, plus you'd have to replace all the stretch bolts etc. It seems that not many heads survive any overheating episodes in the long term, or being taken off & put back on (stresses dues to loosening & tightening), even if they pressure test ok, there seems to be a good chance it'll still be leaking or will start to within a short space of time.

Done some more reading up on cylinder heads etc off site, consensus is that any alu head that is removed should always be skimmed before refit. Pricing in gasket set, skim, pressure test etc and you are not far away from a new fully assembled head with gaskets. So on that thought, maybe I'll just change RAD, PUMP, STAT and new cap and see how I get on with that lot. Also have LCA coming to fit.

If I get another 6 months out of this head at least it will placate the mrs somewhat, even though I know its probably coming.

[stevejt]

Just thought I would update on what appears to be the outcome.

I changed the rad, rad top and bottom hose, water pump, genuine stat, transfered the old rad cap onto the expansion tank. Bled system as per youtube vids, burnt hand in process - hose came off bottom of funnel - ouch.

The hoses I removed looked pretty good. The stat and water pump looked practically brand new, so no need to have done that. I think that in fact the main problem was in fact the header tank cap, even though the rad appeared to have some small weeps.

I fitted an LCA and I-Alert. I used fords 10 year premium antifreeze. Testing the bongo temps range between 78-80 when cruising on motorway around 60mph, not much different around town either, max around 82. Have topped up header tank once by only a small amount, to be expected after initial bleed I've read.

In all probability we lost out on a trip due to a bad seal on the expansion bottle cap.

Steve.