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Mon Apr 13, 2009 10:42 am

Please explain to me how they (watercooled) are all designed to fail open?
If the wax pellet filled element fails it will close or not even open to begin with, right?

Mon Apr 13, 2009 11:54 am

I fully understand that concept, but what the ad says that it LOCKS in open IF there is a overheating condition. An overheat may or may not be the fault of the thermostat. WTF?

Mon Apr 13, 2009 12:11 pm

MAYHEM wrote: Please explain to me how they (watercooled) are all designed to fail open?
If the wax pellet filled element fails it will close or not even open to begin with, right?

Yes, assuming it fails for that reason. If the thermostat fails because the spring broke, it would probably fail open. In my experience, this occurs far less often and to suggest conventional thermostats are designed to fail open is just wrong. If that was the case a failure associated with the wax element would result in a fail open condition and that simply can't happen by virtue of the design of a conventional thermostat.

Perhaps the most accurate statement is that a conventional thermostat is designed to fail open if the failure is the result of the spring failing or debris jamming it open. It is designed to fail closed if the failure is associated with a failure of the wax element.

Mon Apr 13, 2009 12:19 pm

GatorJZ wrote: MAYHEM wrote: Please explain to me how they (watercooled) are all designed to fail open?
If the wax pellet filled element fails it will close or not even open to begin with, right?

Yes, assuming it fails for that reason. If the thermostat fails because the spring broke, it would probably fail open. In my experience, this occurs far less often and to suggest conventional thermostats are designed to fail open is just wrong. If that was the case a failure associated with the wax element would result in a fail open condition and that simply can't happen by virtue of the design of a conventional thermostat.

Perhaps the most accurate statement is that a conventional thermostat is designed to fail open if the failure is the result of the spring failing or debris jamming it open. It is designed to fail closed if the failure is associated with a failure of the wax element.

Thank you. My thoughts exactly.

Mon Apr 13, 2009 12:45 pm

MAYHEM wrote: GatorJZ wrote: MAYHEM wrote: Please explain to me how they (watercooled) are all designed to fail open?
If the wax pellet filled element fails it will close or not even open to begin with, right?

Yes, assuming it fails for that reason. If the thermostat fails because the spring broke, it would probably fail open. In my experience, this occurs far less often and to suggest conventional thermostats are designed to fail open is just wrong. If that was the case a failure associated with the wax element would result in a fail open condition and that simply can't happen by virtue of the design of a conventional thermostat.

Perhaps the most accurate statement is that a conventional thermostat is designed to fail open if the failure is the result of the spring failing or debris jamming it open. It is designed to fail closed if the failure is associated with a failure of the wax element.

Thank you. My thoughts exactly. I hate to break it to you, but I did a lot of researching and like I said, thermostats are supposed to fail open, although there are some out there that will fail closed. The Fail-Safe (which I followed-up on by reading the patent) is designed with an overall override to absolutely fail open.

Mon Apr 13, 2009 12:49 pm

Icy wrote: MAYHEM wrote: GatorJZ wrote: MAYHEM wrote: Please explain to me how they (watercooled) are all designed to fail open?
If the wax pellet filled element fails it will close or not even open to begin with, right?

Yes, assuming it fails for that reason. If the thermostat fails because the spring broke, it would probably fail open. In my experience, this occurs far less often and to suggest conventional thermostats are designed to fail open is just wrong. If that was the case a failure associated with the wax element would result in a fail open condition and that simply can't happen by virtue of the design of a conventional thermostat.

Perhaps the most accurate statement is that a conventional thermostat is designed to fail open if the failure is the result of the spring failing or debris jamming it open. It is designed to fail closed if the failure is associated with a failure of the wax element.

Thank you. My thoughts exactly. I hate to break it to you, but I did a lot of researching and like I said, thermostats are supposed to fail open, although there are some out there that will fail closed. The Fail-Safe (which I followed-up on by reading the patent) is designed with an overall override to absolutely fail open.

Sorry, but there's a difference between design limitations and wishful thinking.

Mon Apr 13, 2009 1:20 pm

Again...the difference is in whether they "fail"...or wear out. There is a difference.

If you keep your thermostat for 100K miles and it craps out and burns up your engine...thast not a failure. Thats stupidity and any self respecting manufacturer of thermostats woudl rightfully show you the finger and laugh at you.

In a failure....and this was the original problem with the first WC thermostats of this type...you usually got corrosion or leakage of the "bulb" area. This vented the wax so the piston could not expand and unseat/open the valve.
The way these thermostats work is that the wax "pellet" will only compress down so small. That minimum compressed height is usually designed in as the bottom stop. If the bulb cracks and the wax vents completely (a manufacturer related failure).....the stopper should then over-extend leaving the thermostat at least partially open in the other direction.

These wax bulbs rarely fail these days unless you let your coolant get so corrosive and old (again your fault so its not a "failure"). What fails.....and this is what I was getting at.....is that the plunger rod gets gunked up with corrosion and the expansion of the wax pellet is not enough force against the spring.
Short of actual defective made in China thermostats (yes it can be a problem)........the most common failure mode is corrosion that impedes proper movement of the opening plate. This includes corrosion of the springs which can break or get weak and cause a full open thermostat that wont close.

So yes......"most" WC thermostats are designed with some margin of safety in them. But the buffer that protetcts most of the manufacturers is that the failure mode that screws most people...can almost always be attributed to poor maintenance. Ray

Mon Apr 13, 2009 2:19 pm

raygreenwood wrote: Again...the difference is in whether they "fail"...or wear out. There is a difference.

If you keep your thermostat for 100K miles and it craps out and burns up your engine...thast not a failure. Thats stupidity and any self respecting manufacturer of thermostats woudl rightfully show you the finger and laugh at you.

In a failure....and this was the original problem with the first WC thermostats of this type...you usually got corrosion or leakage of the "bulb" area. This vented the wax so the piston could not expand and unseat/open the valve.
The way these thermostats work is that the wax "pellet" will only compress down so small. That minimum compressed height is usually designed in as the bottom stop. If the bulb cracks and the wax vents completely (a manufacturer related failure).....the stopper should then over-extend leaving the thermostat at least partially open in the other direction.

These wax bulbs rarely fail these days unless you let your coolant get so corrosive and old (again your fault so its not a "failure"). What fails.....and this is what I was getting at.....is that the plunger rod gets gunked up with corrosion and the expansion of the wax pellet is not enough force against the spring.
Short of actual defective made in China thermostats (yes it can be a problem)........the most common failure mode is corrosion that impedes proper movement of the opening plate. This includes corrosion of the springs which can break or get weak and cause a full open thermostat that wont close.

So yes......"most" WC thermostats are designed with some margin of safety in them. But the buffer that protetcts most of the manufacturers is that the failure mode that screws most people...can almost always be attributed to poor maintenance. Ray

Lost it with the first line:

fail
5 entries found.

1. 1fail (verb)
2. 2fail (noun)
3. 1fail–safe (adjective)
4. 2fail–safe (noun)
5. pass–fail

Main Entry:
1fail Listen to the pronunciation of 1fail
Pronunciation:
\ˈfāl\
Function:
verb
Etymology:
Middle English failen, from Anglo-French faillir, from Vulgar Latin *fallire, alteration of Latin fallere to deceive, disappoint
Date:
13th century

intransitive verb1 a: to lose strength : weaken <her health was failing> b: to fade or die away <until our family line fails> c: to stop functioning normally <the patient's heart failed>2 a: to fall short <failed in his duty> b: to be or become absent or inadequate <the water supply failed> c: to be unsuccessful <the marriage failed> ; specifically : to be unsuccessful in achieving a passing grade <took the exam and failed> d: to become bankrupt or insolventtransitive verb1 a: to disappoint the expectations or trust of <her friends failed her> b: to miss performing an expected service or function for <his wit failed him>2: to be deficient in : lack <never failed an invincible courage — Douglas MacArthur>3: to leave undone : neglect <fail to lock the door>4 a: to be unsuccessful in passing <failed chemistry> b: to grade (as a student) as not passing
— fail·ing·ly Listen to the pronunciation of failingly \ˈfā-liŋ-lē\ adverb

Mon Apr 13, 2009 4:19 pm

raygreenwood wrote: (sigh).... :roll: all thermostats are desigend to fail in the open position. However, that depends on what causes them to fail.
The primary reason a lot of watercooled thermostats fail in the closed position is because of corrosion...not from the element and spring failing...which are the parts designed to fail open.

Also...as mentioned....you cannot run most "modern" cars with no thermostats. The Humvee is a great mention. That function is specifically one of the many things desigend into the hummer to make it tough as nails...along with EMP suppression for the ignition, waterproofing of ingition, shock proof dash gauges, fill on the fly tire airing system sand deep water wading capability.

Modern fuel injected waterpumpers...quickly drop into gas guzzling limp home mode when the thermostat fails open, closed....or is removed. Some cars can bearly run this way and its not great for the car.

ACVW's.....all fail in the open position. Ray

Unfortunately not true. There are/were Mexican made thermostats that used a wax pellet instead of the original bellows. They fail closed. Berg even sold them for a while. I have a couple that I would be very happy to sell you. Their mounting bracket is a little different than the bellows style, but the original bracket can be easily modified to work. I used the Mexican ones for a while, but was never comfortable with them. I now have 5 or 6 NOS bellows ones. If the price continues to rise, they may be my retirement.

Mon Apr 13, 2009 4:22 pm

spanky324 wrote: Anyone tried the Failsafe thermostat they advertise on Two Guys Garage they do list one for aircooled VWs? I talked to the tech dept-They dont have any here in USA but they do carry them in there Germany branch for aircooled vws!!

Mon Apr 13, 2009 4:25 pm

spanky324 wrote: spanky324 wrote: Anyone tried the Failsafe thermostat they advertise on Two Guys Garage they do list one for aircooled VWs? I talked to the tech dept-They dont have any here in USA but they do carry them in there Germany branch for aircooled vws!!

Were they able to direct you to a picture of one?

Tue Apr 14, 2009 9:52 am

no he didnt!

Tue Apr 14, 2009 10:15 am

I've had several waterpumper thermostats fail over the years... never burned up an engine because they all failed open... by design? I'd hope so, but I didn't design them nor do I care to research the design... I've had a few failed ACVW thermostats over the years(yeah I run them in *every* vw, even with large engines) all but one failed open...

Tue Apr 14, 2009 10:47 am

Gatorjz.....since you lost it in the first line...I'll spell it out for you so you don't overheat yourself...and won't have to list a half page of un car-related crap expressing your confusion.

Its like this.....
(1)your engine throws at rod at 40,000 miles with perfect tuning, parts, compression, fuel mixture, cooling and driving styles. Failure of a part? Most probably. Fault of the part? Most probably.

(2) Your engine throws a rod at 240,000 miles with perfect tuning, parts, compression, fuel mixture, cooling and driving styles.
Failure of a part? Probably several. Fault of the part....no...doubtful. It was time to rebuild and your failure to notice gradual changes in tolerance, efficiency and compression and rebuild before you "grenade" the engine....are your fault.

(3) Your engine throws a rod at 50,000 miles with perfect tuning, parts, compression, fuel mixture, cooling and driving styles...except that you changed the oil only after break-in
Failure of a part? Probably most of them. Fault of the part?...no your fault.

All of these are the same failure...for different REASONS. The manufacturers of T-stats these days (and many other parts) build in fail-safes to cover what could be their fault....no driver negligence.

Disect a few thermostats...and it becomes plainly obvious what happens when they corrode (and vent the expansion pellet) versus when they corrode and can no longer move. The vast majority are designed to open to a "fail-safe" position....when...and here is the kicker.....when the thermostat fails due to any reason that can be construed as a construction defect (that would be soldering or crimping) or from a material defect (alloy, galvanic corrosion due to dissimilar metals etc.).

In all of those cases, the operative mechanism that moves the thermostat (the wax pellet)...would vent...rendering the T-stat ineffective. Most WC thermostats are designed to fail in a safe position. Its manufacturers covering their backside.

Likewise....jamming of the central shaft, the bearing point of that shaft or any of the mechanical movement by corrosion or debris....read that as any other failure method.....can only be caused by incorrect or poorly maintained coolant. In those cases....the T-stat will generally NOT fail in a safe position.
Since the maintenance and composition of your coolant......has nothing to do with the manufacturer......I would tend to agree with their position.

Also do a bit of historical research and you will find out that back in the 50's...there were issues with construction (soldered and crimped) and with materials (brass, copper bronze and various combinations)...of all T-stats.
There were too many problems....too many lawsuits.
I have driven enough company and fleet vehicles...two of which had major cooling systems failures with low miles. When you end up at the dealer debating whether it was the T-stats fault or the car manufacturers fault....These enlightening details above will be explained to you.
It is only recently with Cheap overseas made T-stats...that the auto industry is eeing a rash of failures (about the last 5 years). Otherwise...for the few failures modern thermostats have had (within the warranty of the T-stat manufacturers....ie....to do with the chamber and wax bulb and nothing else) ...you find the T-stat companies paying out on a regular basis...when it can be proven that their parts failed.

TWD....thanks for the info. I have never seen a non-bellows variety of ACVW T-stat.
In general...with the bellows variety...I have never seen a non-safe failure...except in the few cases where spring tension on the system was not correct.
In that case...its not the fault of the bellows...but the operator. I guess the real categories of failure would be....correctly installed and adjusted failures or incorrectly installed and adjusted failures.Ray

Tue Apr 14, 2009 11:57 am

Ray...let me dumb this down for you....when a thermostat stops working properly, it has failed.

Tue Apr 14, 2009 12:02 pm

that's a stretch.... if it failed to do it's job, then it did just that... I have a couple bald tires that fail to do their job properly, but they haven't suffered a failure...

Tue Apr 14, 2009 12:44 pm

Written in stone: "If a watercooled engine OVERHEATS for any reason in most instances the thermostat will then fail closed due to the overheated condition". This has been going on for as long as watercooled engines have had thermostats. So if this new design prevents it from closing when the engine overheats it is definitely an improvement.