DOC4444 wrote:
Kap,
What exact vehicle thermostat are you using? When I get a unit from you, I want to use a MotoRad, which fails OPEN. (I brought this up months ago and several people literally flamed me.) I have had two motors over the years ruined by thermostats that failed CLOSED and know several other cases of the same thing.
I never use anything but MotoRad thermostats when I have a choice.
DOC
Yes, 1999 Hyundai Accent, 1.5L SOHC.
I have been using a MotoRad on all units so far. I do like their quality. MotoRad does not mecessarily mean "Failsafe" however, they make both versions. See the pics at teh bottom of this post. I think due to their quality and engineering they do tend to fail by opening early, not late. I will explain more on this and why later.
They also have a 192ºF failsafe option for $13 and annother 192ºF failsafe option for $17 (not sure the difference between the 2, but the $17 is special order and probably going away, the $13 is listed as a stocked item). Additionally the regular 192º price went down to $10, the 180º is still $12. I did not however find a 180ºF failsafe option from them, at least on the autozone website since i buy there locally.
A "failsafe" thermostat, by the way, only means
if the vehicle overheats, it will allow (when temp is high enough - probably 250ºFish) for the piston to push the thermostat open far enough to catch on physical hardware and not ever close again. I would never let my temp get that high and would just pull over and pull out the thermostat instead of letting my vehicle get that hot if that was the case.
I personally believe it is 90% marketing and 10% function only. It doesn't necessarily prevent the piston assembly itself from gradually leaking out the wax that causes it to expand like all thermostats and it can fail just like any other thermostat unit in the closed position. If the wax has leaked out enough, it will not open far enough to catch on the fail safe hardware and then not fail open...eventually it will fail closed unless the spring fatigues first like any other thermostat.
A failsafe is great in the case that your cooling fan clutch has gone out and your temps rise enough to open it further and lock to help cooling a bit, but that is all it does. It's design is to have a locking mechanism that catches right before the piston is fully extended and the wax leaks out.
A regular thermostat does the same thing w/exception of it will close again after (and still funcition) unless the design lets the piston come all the way out and the wax leaks out rapidly in which case it could fail closed,
but ONLY after you vehicle is well past the design spec operating temperature for the engine.
And if the cooling system is that hot, you need to shut your vehicle down - preferably WAY before it gets that hot!!! In fact the CRD starts cutting fuel to the engine at 225ºF and fully cuts fuel to the engine at 243ºF, Cluster chime for overheating is at 244ºF based on GDE's info.
Anyway, if you get close to the 3/4 mark on teh coolant gauge (230ºF), something is wrong w/ your cooling system and you need to shut down. Do not let your CRD shut down on its own at 245º - That is just not good for the engine and can cause BAD stuff like head gasket failure, etc. Not worth the $$$$ to fix when you could prevent it w/ correcting the cooling system issue.
The failsafe is an option I am happy to offer. My only recommendation is that regardless what you use, keep a spare...they are only about $10 and you only need a 10mm socket/ratchet to change it on the road. Even if you don't have a spare, the housing is also designed in such a way that you can reassemble w/o a thermostat at all in the case that a thermostat failed closed. If this ever happens, the thermostat can be removed and the unit reassembled and you can get to your destination w/ the port completely open and then get a new thermostat ASAP.
In any case, todays thermostats are designed to allow the metal spring to fatigue before the piston surrounding wears and lets wax leak out. the only exception is if the thermostat is severely overheated (caused by annother cooling system component failing first) and the piston comes out of the housing completely. Spring fatigue is how every factory thermostat in our CRD's has failed that I know of. The spring has weakened and let it open early, bad for economy, but better fail open than closed. Good for about 50k miles on most designs it seems.
I did notice the spring on the MotoRad was not as stiff as the spring on the Stant. This can be good...or bad...
If the spring is stiff enough to never fail, it will then wait for the piston seal to fail and will fail in the closed position (bad) but you will probably get 100k miles out of a thermostat instead of 50k miles. It could be possible that it is a better design and will let the spring fail around 100k and the piston still outlast the spring which would be good.
If the spring is too soft you will get premature failure at 50k or less and thermostat life is shortened causing more maintenance. Personally a thermostat change is minor maintenance in my book and I would rather change a $10 part and spend 20min doing it every 50k miles with it failing opening to earily and loosing a tiny bit of economy until i notice it and be able to change it in my own time allowing me to schedule a change rather than have one fail closed and overheat and possibly damage the engine/blow a head gasket, etc and leave me stranded if I don't notice the temp creeping up even if it lasts 2-3 times as long.
We don't have any data for long term reliability of the new thermostat since no one has been running a MotoRad in the CRD for long enough yet
All that being said, it can't hurt to go the $3-7 extra for a failsafe though it only adds a minor ammount of protection in my opinion and
only in the case annother cooling system component fails and you let your engine over heat. It looks like the spring is the same on the MotoRad failsafe and the non failsafe from MotoRad so life should be about the same and it will most likely fail opening too early at least earlier than the stant one which is on the safe side.
Here is the standard MotoRad:
Here is the Failsafe MotoRad:
**note** from autozone they are boxed "Duralast" brand, but are marked on the thermostat itself "MotoRad"
Please notice the piston unit in both versions from the same manufacturer adn the springs are the same. Only the additional hardware catch is different. This means both will fail by overextending the piston and leaking wax at the same temp when forced too far open by too hot of a temperature. Again, like I mentioned, when this happens you engine is already too hot and needs to be shut down - preferably before this happens. It may not even be possible to reach this temp since the CRD shuts down automatically w/fuel cutoff.
Oh, if you read all that you were forced to listen to my
again!
I at least hope it was a good read and all useful information.
**EDIT**
Here is a video of both standard and failsafe thermostats failing at the undisclosed temp (REALLY HOT - guessing around 250ºF) side by side after a vehicle has already overheated for some other reason (fan failure, etc.):
http://www.youtube.com/watch?v=LTz4Buuy_c8 - listen carefully:
1) "failsafe thermostats fail in an open position" - yes, but can also fail closed like any other thermostat if the wax leaks out over time.
2) "they will
help to keep your engine from blowing" - yes, "help"
only if you continue to drive on an extremely overheated engine
3) "lessening the chance for expensive engine damage" - carefully choosing their words again (only if you continue to drive at an overheated temp)
4) "when overheating does occur, the thermostat will fail" - Duh, they all do, failsafe or not...and if it needs to overheat to fail and lock open, how does this help again?!? Won;t I want to shut the engine down before being extremely hot - hot enough ot lock the thermostat open?
5) "the failsafe thermostat contains these 2 additional components" - Really??? your non failsafe thermostat has the same wax resivoir, same piston, same spring, etc. How is this circled wax resivoir component different?
6) "the coolant continues to circulate which could save your engine" - if your engine has to have a component other than the thermostat fail first to obverheat which will allow the failsafe thermostat to then fail open (and only then - after extreme engine temps are reached), it really doesnt keep your engine cool at all if the other component that caused overheating is still failing and you will still be overheated!!! I guess you will increase temp slower at this piont since the other thermostat would have closed by now...but again...why keep driving at this point???!??
Regardless of it failing open or closed, by the time this hits the temp to "fail open" or the other one fail and close, you will have already shut down your engine so almost pointless in my opinion...again marketing because they want your $$$ but like I said it can't hurt. <-- more of my
but, don't complain, I'm giving $ away 2 cents at a time.
I am not saying people shouldn't go for the failsafe, not at all. I just want to clear up the myth that people think it can't fail closed like any other thermostat. That is simply not true. It only locks open if it was already functioning properly when you overheat caused by annother component in the cooling system failing. <-- can;t stress that enough.
By gradually wearing the piston sleeve through normal use, wax will eventually leak out on both the failsafe and the non failsafe and they will fail closed at the same time if the thermostat is not replaced before the piston wears out.
Again, to be clear - If the piston sleeve wears and the wax leaks out, the failsafe WILL fail closed, you WILL overheat, and the "failsafe" function will never be used. Usually the thermostat spring weakens and allows early opening and the engine to run cool well before the piston sleeve wears out. Given that it's $3 more it certanly can't hurt to go for it and I ma happy to install whichever you choose. They both fit and honestly, this is not an important decision unless it helps you sleep better at night.
- Mark
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I wish you didn't live all the way up there in Canada, if you were a few states closer we'd be hangin out more. 
