Do thermostats get 'tired'?

[Lewy]

Having replaced my rad and a couple of hoses and changing coolant etc. but rather shortsightedly not changing the stat , I still notice that the MAson damped temp guage reads higher than it used to - especially on long sustained climbs. I seem to remember being able to see much more dramatically the moments when the stat opened and the needle started to drop - it still happens, but happens later and seems to be slower.

Although it could be the Mason calibration has become a bit unreliable, it does sometimes peep erratically for no reason.

Anyway - do stats get worn or tired? Can you get a lower temp rated stat that opens a bit earlier - I seem to remember some talk of drilling them out?

[missfixit70]

When I tested my new one against my old one in a pan of boiling water, the new one opened sooner & stayed open longer as it cooled, definitely worth changing if it's suspect, check it against the one you take out to see for yourself if there's a difference.

[ScubaBongo]

Is it true it's a hard job if you're 4wd?

[You've Been Bongod]

isn't there a liquid you can add to cool the temp down on a bongo and other vehicles ??

i am sure dbo mentioned it

[waycar8]

isn't there a liquid you can add to cool the temp down on

Yep its called water wetter

Having replaced my rad and a couple of hoses and changing coolant etc. but rather shortsightedly not changing the stat , I still notice that the MAson damped temp guage reads higher than it used to - especially on long sustained climbs. I seem to remember being able to see much more dramatically the moments when the stat opened and the needle started to drop - it still happens, but happens later and seems to be slower.

Although it could be the Mason calibration has become a bit unreliable, it does sometimes peep erratically for no reason.

Anyway - do stats get worn or tired? Can you get a lower temp rated stat that opens a bit earlier - I seem to remember some talk of drilling them out?

Change the stat it might be sticking, or you might have an air lock still. dont drill the thermostat for what it will cost for new one compared to the "hiding" of a overheating issue?, the reason why people drill the stats is to hide an issue with the system I believe, and if yours has never overheated then theres no need to drill it all thoe the stat does have a nipple type thing on one side and has a bar going through the stat then a nipple on the other side so it can move from side to side to help release any air the one I bought had this on and the only possible reason for it being there is to relese air??

[Lewy]

Thanks for those replies - spoke to Allans in Plymouth and he mentioned that if an engine has been running a bit warm they can start to play up so booked it in for him to do. Although fairly handy around cars Allan's last bleed of the system was faultless and quick so I reckon its worth a few quid to get him to do it again and make sure the system is fully up to spec as we're off on our travels soon and those Cornish hills are pretty steep.

On another point, has anyone had a Mason alarm act-up - I wonder if perhaps its not running hotter, maybe its the measuring tool that is inaccurate?

[Peg leg Pete]

I agree with you wayne and missfixit I think with a F.W.D the front drive shaft might make changing the stat a little trickier

[maxheadroom]

No it can be done without removing the drive shaft you need a long reach socket set
I have changed mine and had it out so to speak to check it.

[Peg leg Pete]

I stand corrected sir

[sandstone]

The reason for holes on stats is usually:

1. To allow trapped air to circulate out of the system when filling.
2. To prevent a stagnant area of coolant between the engine's heat generating surfaces and the thermostat's wax capsule. A stagnant area would slow down the response of the thermostat and accuracy of control.

Item 2. above usually applies to engines with "constant outlet temperature" control where the thermostat is on the outlet, and responds to outlet temperature changes.

The Bongo engine uses a "constant inlet temperature" system, with the thermostat on the inlet. The wax capsule in the mixing chamber of the thermostat senses the temperature of the re-circ line. When this reaches 82 degsc the thermostat opens and cool fluid is admitted from the radiator circuit. A stagnant area is therefore avoided.
This initial opening of the thermostat after a system re-fill is also the point at which trapped air in the radiator/thermostat hose is released into the system, about which so much has been written on these pages. The bleeding procedure eliminates this air once it has been released from the hose. In other words when the thermostat opens and the hose get warm.

The "constant inlet temperature" system gives a tight temperature control on fluid entering the engine even with varying engine speed and changing ex-radiator coolant temperature. After warm-up, when the thermostat has taken control, the system can react quickly to inlet coolant temperature changes caused by surges of cold fluid such as when engine speed increases. An outlet control system can only sense the temperature of coolant after it has passed through the engine, when it is too late, with the resultant thermal shock to the engine. The Bongo system eliminates this.

[mikeonb4c]

The reason for holes on stats is usually:

1. To allow trapped air to circulate out of the system when filling.
2. To prevent a stagnant area of coolant between the engine's heat generating surfaces and the thermostat's wax capsule. A stagnant area would slow down the response of the thermostat and accuracy of control.

Item 2. above usually applies to engines with "constant outlet temperature" control where the thermostat is on the outlet, and responds to outlet temperature changes.

The Bongo engine uses a "constant inlet temperature" system, with the thermostat on the inlet. The wax capsule in the mixing chamber of the thermostat senses the temperature of the re-circ line. When this reaches 82 degsc the thermostat opens and cool fluid is admitted from the radiator circuit. A stagnant area is therefore avoided.
This initial opening of the thermostat after a system re-fill is also the point at which trapped air in the radiator/thermostat hose is released into the system, about which so much has been written on these pages. The bleeding procedure eliminates this air once it has been released from the hose. In other words when the thermostat opens and the hose get warm.

The "constant inlet temperature" system gives a tight temperature control on fluid entering the engine even with varying engine speed and changing ex-radiator coolant temperature. After warm-up, when the thermostat has taken control, the system can react quickly to inlet coolant temperature changes caused by surges of cold fluid such as when engine speed increases. An outlet control system can only sense the temperature of coolant after it has passed through the engine, when it is too late, with the resultant thermal shock to the engine. The Bongo system eliminates this.

Excellent post and very informative - thanks+++

[cheffy34]

i think i understood it


dar

[stevedon]

its dead easy on a 4wd mine took all of 15 mins 10mm socket wobble extention drive and your away.do it from underneath tho

[stevedon]

over a period of time thermostats get weak as all mechanical things do.replace it as it made a major difference to mine and many an engine has been ruined by a £10 thermostat

[Lewy]

Brilliant replies as ever.

New stat it is then next week - I will post back when its done - hopefully with positive results and a slightly cooler running engine!

Lewy