silicone paste?
William R. Watt
my distributor with one out of a distributor I bought from a wrecker. I
read up on ignition systems in a couple of library books. One suggested
applying a silicone paste between the ICM and the distributor to protect
the ICM from engine heat. I've seen a white paste on the heat sink of a
couple of computer CPU's I've removed from old computers. When I took the
ICM off the distributor I bought it looked like there was a clear grease
or something between the ICM and the distributor. There wasn't anything on
the ICM on my car, which had been replaced by a service station in 1999.
Can anyone tell me what, if anything, I should ptu between the ICM and the
distributor? If I were to get something at an auto parts store what should
I ask for?
thank you.
--
------------------------------------------------------------------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-freenet email must have "notspam" in subject or it's returned
Bruce Chang
that you put on the spark plug boots to keep them from sticking to the spark
plug.
-Bruce
"William R. Watt" <ag...@FreeNet.Carleton.CA> wrote in message
news:btcoqi$b4l$1...@freenet9.carleton.ca...
John Ings
Watt) wrote:
>I'm about to replace the malfunctioning ignition control module (ICM) in
>my distributor with one out of a distributor I bought from a wrecker. I
>read up on ignition systems in a couple of library books. One suggested
>applying a silicone paste between the ICM and the distributor to protect
>the ICM from engine heat. I've seen a white paste on the heat sink of a
>couple of computer CPU's I've removed from old computers.
That stuff is just what you DON'T want. It has zinc oxide in it and is
formulated to conduct the maximum amount of heat.
>When I took the
>ICM off the distributor I bought it looked like there was a clear grease
>or something between the ICM and the distributor.
Yes. Silicone dialectric grease.
http://www.classicgarage.com/noname25.html
It looks like vaseline. Auto parts stores will have it. Good for the
job you mention, waterproofing electrical disconnects, keeping park
light bulbs from corroding and siezing in their sockets...lots of
other uses. Good stuff.
L0nD0t.$t0we11
> On 5 Jan 2004 22:34:58 GMT, ag...@FreeNet.Carleton.CA (William R.
> Watt) wrote:
>
>>I'm about to replace the malfunctioning ignition control module (ICM) in
>>my distributor with one out of a distributor I bought from a wrecker. I
>>read up on ignition systems in a couple of library books. One suggested
>>applying a silicone paste between the ICM and the distributor to protect
>>the ICM from engine heat. I've seen a white paste on the heat sink of a
>>couple of computer CPU's I've removed from old computers.
>
> That stuff is just what you DON'T want. It has zinc oxide in it and is
> formulated to conduct the maximum amount of heat.
Actually not that effective. For good heat transfer, you want
something like Arctic Silver, which contains colloidal silver.
Some of the white stuff is also a titanium compound, tends to
be a bit "whiter" than zinc oxide.
Not that I would guess either would be a good idea.
>
>>When I took the
>>ICM off the distributor I bought it looked like there was a clear grease
>>or something between the ICM and the distributor.
>
> Yes. Silicone dialectric grease.
>
> http://www.classicgarage.com/noname25.html
>
> It looks like vaseline. Auto parts stores will have it. Good for the
> job you mention, waterproofing electrical disconnects, keeping park
> light bulbs from corroding and siezing in their sockets...lots of
> other uses. Good stuff.
Unless you get it between the battery post and the terminal,
where you discover what "dielectric" really means.
--
Fan of the dumbest team in America.
do_not_spam_me
> I'm about to replace the malfunctioning ignition control
> module (ICM) in my distributor with one out of a distributor
> I bought from a wrecker. I read up on ignition systems in a
> couple of library books. One suggested applying a silicone
> paste between the ICM and the distributor to protect the
> ICM from engine heat. I've seen a white paste on the heat
> sink of a couple of computer CPU's I've removed from old
> computers. When I took the ICM off the distributor I bought
> it looked like there was a clear grease or something between
> the ICM and the distributor. There wasn't anything on the
> ICM on my car, which had been replaced by a service station
> in 1999.
Whoever said that the paste is for insulating the ICM from engine heat
was dead wrong, and auto mechanics are often wrong about electronics.
The purpose of the paste is to conduct heat _away_ from the ICM and
into the engine, which, amazingly, is actually cooler, and if the ICM
really had to be insulated from engine heat, it wouldn't be mounted
inside anything as hot as a distributor. Some transistors are rated
for 200 Celcius (not Fahrenheit) continuous use.
Get some dielectric grease, made of silicone oil mixed with zinc
oxide. Loctite makes some, and it's commonly applied to spark plug
boots to seal them from moisture, but Radio Shack (no. 276-1372) and
electronic parts supplies sell it as heatsink grease. Don't get
anything runny, like Dow Corning DC4 or DC22, which will drip and
attract gas and oil fumes that will form carbon tracks; the Loctite
and Radio Shack products are thick enough. And don't ever use any
substance that bears metal powder, like Arctic Silver, a heatsink
grease made for computer processor chips, because it conducts
electricity well enough to create shorts at high voltages. The makers
of the product deny that it conducts significantly, but they also said
not to use it inside a TV, where some of the voltages are in the same
range as those of automotive ignition systems.
I don't know why your previous ICM had no silicone grease on it, but I
suspect that's why it failed so soon. I've never handled a factory
ICM myself, but I did tinker with a couple of homemade electronic
ignitions for myself back in the 1970s, and I always used silicone
grease or RTV on the transistors and SCRs. I never had a failure,
except when rain leaked in a box I failed to seal and when distributor
caps cracked every few weeks from excessive voltage (my first try at
CD ignition, adding regulation stopped the cracking).
Bob Paulin
William R. Watt <ag...@FreeNet.Carleton.CA> wrote in article
<btcoqi$b4l$1...@freenet9.carleton.ca>...
> I'm about to replace the malfunctioning ignition control module (ICM) in
> my distributor with one out of a distributor I bought from a wrecker. I
> read up on ignition systems in a couple of library books. One suggested
> applying a silicone paste between the ICM and the distributor to protect
> the ICM from engine heat. I've seen a white paste on the heat sink of a
> couple of computer CPU's I've removed from old computers. When I took the
> ICM off the distributor I bought it looked like there was a clear grease
> or something between the ICM and the distributor. There wasn't anything
on
> the ICM on my car, which had been replaced by a service station in 1999.
>
> Can anyone tell me what, if anything, I should ptu between the ICM and
the
> distributor? If I were to get something at an auto parts store what
should
> I ask for?
>
You should ask for silicone heat-transfer compound. It is used to transfer
heat away from the module into the breaker plate.
Silicone di-electric compound is NOT the same thing. Di-electric compound
has electrical insulation qualities that helps keep sparks from jumping
around. That is why it is used on spark plug wires.
Bob Paulin - R.A.C.E.
Race Car Chassis Setup and Dial-in Services
Bob Paulin
Jimmy <nop...@nowhere.not> wrote in article
<fanlvv4b406k00qu2...@4ax.com>...
> On Tue, 06 Jan 2004 06:34:11 -0600, "Bob Paulin" <ra...@mint.net>
> wrote:
>
> >Silicone di-electric compound is NOT the same thing. Di-electric
compound
> >has electrical insulation qualities that helps keep sparks from jumping
> >around. That is why it is used on spark plug wires.
>
> I thought it was just to make the boots easier to remove next time
> and the insulating properties were a requirement for that job.
>
Di-electric compound is meant to seal the electrical connection from
external corrosive elements. It is used at points other than spark plug
boots around the car such as lamp sockets.
Making the boots easier to remove is merely a great side benefit.
do_not_spam_me
> You should ask for silicone heat-transfer compound. It is used
> to transfer heat away from the module into the breaker plate.
>
> Silicone di-electric compound is NOT the same thing. Di-electric
> compound has electrical insulation qualities that helps keep sparks
> from jumping around. That is why it is used on spark plug wires.
Dielectric compound is not _necessarily_ the same thing as heat
transfer compound, but in practice it's identical -- silicone oil
mixed with zinc oxide powder. The exception are silver-bearing heat
transfer compounds marketed toward ignorant computer users. But any
silicone heat transfer compound made for high voltage use, like
ordinary Radio Shack Transistor Heatsink Grease, Tech Spray Heat Sink
Compound, or GC Electronics heatsink grease, will also be dielectric
compound. Some of heatsink compounds aren't made with silicone grease
but instead with ester oil and are labelled "silicone-free," but I
don't know if they're safe for automotive plastics and rubbers, so I'd
avoid them. Also some silicone-based compounds contain very little
zinc oxide or other oxides and can drip (Dow Corning DC-4 is notorious
for this) and should not be used on ignition systems, especially not
around the distributor.
do_not_spam_me
> > On 5 Jan 2004 22:34:58 GMT, ag...@FreeNet.Carleton.CA (William R.
> > Watt) wrote:
>>> I read up on ignition systems in a couple of library books.
>>> One suggested applying a silicone paste between the ICM and
>>> the distributor to protect the ICM from engine heat. I've
>>> seen a white paste on the heat sink of a couple of computer
>>> CPU's I've removed from old computers.
>
>> That stuff is just what you DON'T want. It has zinc oxide in
>> it and is formulated to conduct the maximum amount of heat.
>
> Actually not that effective. For good heat transfer, you want
> something like Arctic Silver, which contains colloidal silver.
> Some of the white stuff is also a titanium compound, tends to
> be a bit "whiter" than zinc oxide.
You do not want Arctic Silver around high voltage equipment. It is
not a dielectric, Arctic Silver co. has warned against using it in
TVs, and I know of one horizontal output transistor (voltage similar
to ignition primary's) that instantly failed when it was used. It's
also false that zinc oxide bearing grease doesn't conduct heat well;
otherwise it wouldn't be in the grease used on almost every transistor
and power IC mounted against a heatsink, such as inside the better
computer power supplies.
>> It looks like vaseline. Auto parts stores will have it. Good for
the
>> job you mention, waterproofing electrical disconnects, keeping park
>> light bulbs from corroding and siezing in their sockets...lots of
>> other uses. Good stuff.
>
> Unless you get it between the battery post and the terminal,
> where you discover what "dielectric" really means.
Wrong again. The grease will be pierced and squeezed out by
mechanical pressure and won't interfere at all with electrical
conduction but will simply seal out liquids. This is why high-amp
slide switch contacts are often coated with dielectric grease before
assembly, and even GE silent mercury wall switches have been. Anyone
who coats battery terminals with grease after assembly isn't doing the
job right.
William R. Watt
> I'm about to replace the malfunctioning ignition control module (ICM) in
> my distributor with one out of a distributor I bought from a wrecker. I
from the responses there seems to be trwo functions
1. electrical insulation (di-electric, ie "non-conducting")
2. heat dissipation
I looked at the pastes at Radio Shack and at the auto parts store. The
Radio Shack store was a small one and not well stocked but the clerk did
find a very small container of the "heat sink grease" for $10. The package
did not mention any di-electic property but I think it was reported in
this thread that this paste is di-electirc. That's all this radio Shack
store had. The auto parts store had two brands of silicone di-electric
paste at $5 and $8. The lower priced one was a store brand. Listed on the
back of one of the packages were recommended applications including
"ignition modules". I didn't read anything on the packages at the auto
parts store about heat dissipation.
I'm wondering what it is that gives paste its heat dissipating quality and
if the cheaper pastes at the auto parts stores would dissipate heat.
Mark Olson
> William R. Watt (ag...@FreeNet.Carleton.CA) writes:
> > I'm about to replace the malfunctioning ignition control module (ICM) in
> > my distributor with one out of a distributor I bought from a wrecker. I
>
> from the responses there seems to be trwo functions
> 1. electrical insulation (di-electric, ie "non-conducting")
> 2. heat dissipation
>
> I looked at the pastes at Radio Shack and at the auto parts store. The
> Radio Shack store was a small one and not well stocked but the clerk did
> find a very small container of the "heat sink grease" for $10. The package
> did not mention any di-electic property but I think it was reported in
> this thread that this paste is di-electirc. That's all this radio Shack
> store had. The auto parts store had two brands of silicone di-electric
> paste at $5 and $8. The lower priced one was a store brand. Listed on the
> back of one of the packages were recommended applications including
> "ignition modules". I didn't read anything on the packages at the auto
> parts store about heat dissipation.
>
> I'm wondering what it is that gives paste its heat dissipating quality and
> if the cheaper pastes at the auto parts stores would dissipate heat.
http://www.wakefield.com/pdf/accessories.pdf
"The 120 Series Silicone Oil-Based Thermal Joint Compound fills the minute
air gap between mating surfaces with a grease-like material containing
zinc oxide in a silicone oil carrier. It possesses an excellent thermal
resistance of only 0.05[deg]C/W for a 0.001 in. film with an area of one
square inch."
Rex B
an issue. It's usually white opaque, whereas the dielectric grease looks like
Vaseline.
On Mon, 05 Jan 2004 22:38:52 GMT, "Bruce Chang" <bec...@swbellnospam.com>
wrote:
Rex in Fort Worth
L0nD0t.$t0we11
>
> You do not want Arctic Silver around high voltage equipment.
True.
> It's also false that zinc oxide bearing grease doesn't conduct heat well;
No, but it IS true that it isn't even in the same ballpark
for heat transfer efficiency as colloidal silver.
> otherwise it wouldn't be in the grease used on almost every transistor
> and power IC mounted against a heatsink, such as inside the better
> computer power supplies.
Ummm, Arctic Silver is
a common way to cool a hot Pentium, and is approved by Intel
as not voiding the warranty on their Pentiums... at least for
an OEM manufacturer that might give them grief about those
cheesy thermal pads.
do_not_spam_me
> The Radio Shack store was a small one and not well stocked
> but the clerk did find a very small container of the "heat
> sink grease" for $10.
> The auto parts store had two brands of silicone di-electric
> paste at $5 and $8. The lower priced one was a store brand.
> I'm wondering what it is that gives paste its heat dissipating
> quality and if the cheaper pastes at the auto parts stores
> would dissipate heat.
It dissipates heat mostly because it's much denser than air. About
any liquid or solid that fills the gaps will be about 50 times as good
as air, and in practice anything that doesn't drip or evaporate will
work. Metal oxide powders, most often zinc oxide, are usually added
so dielectric grease to prevent dripping and improve heat conduction.
In a pinch you can use high temperature grease, but it can make damage
vinyl and turn it into hard cheese, but I'd probly use silicone rubber
sealant (RTV) instead.
Steve
> ag...@FreeNet.Carleton.CA (William R. Watt) wrote in message news:<bth1q1$bda$1...@freenet9.carleton.ca>...
>
>
>>The Radio Shack store was a small one and not well stocked
>>but the clerk did find a very small container of the "heat
>>sink grease" for $10.
>
>
>>The auto parts store had two brands of silicone di-electric
>>paste at $5 and $8. The lower priced one was a store brand.
>
>
>>I'm wondering what it is that gives paste its heat dissipating
>>quality and if the cheaper pastes at the auto parts stores
>>would dissipate heat.
>
The clear "dielectric" grease found at parts stores isn't a great heat
conductor because its pure grease. Its questionable whether it might
even be WORSE than bare metal-to-metal. The white "heat sink grease" is
better because its loaded with fine metal-oxide particles (zinc oxide, I
imagine) that do conduct heat much better than the grease without being
a good electrical conductor. There are still better heat-conducting
greases that can be used where electrical insulation isn't needed or is
desired (like silver powder loaded grease and copper powder loaded
grease). Those can be used, for example, between a transistor's
collector thermal pad and a heatsink in a common-collector ("emitter
follower") amplifier circuit.
William R. Watt
> The clear "dielectric" grease found at parts stores isn't a great heat
> conductor because its pure grease. Its questionable whether it might
> even be WORSE than bare metal-to-metal. The white "heat sink grease" is
> better because its loaded with fine metal-oxide particles (zinc oxide, I
> imagine) that do conduct heat much better than the grease without being
> a good electrical conductor. There are still better heat-conducting
> greases that can be used where electrical insulation isn't needed or is
> desired (like silver powder loaded grease and copper powder loaded
> grease). Those can be used, for example, between a transistor's
> collector thermal pad and a heatsink in a common-collector ("emitter
> follower") amplifier circuit.
>
the di-electric paste at the auto parts store has "heat resistant"
written on it which I assume means it will not deform when heated.
I hope it does not mean that is acts as a thermal insulator. I do
have a pot of heat resistant wheel bearing grease. :)
the ICM is black plastic with a stamped white metal base and
two bolt holes lined with metal. around the edge between the metal
base and the plastic body is a dried white paste which looks like
it bled out and was wiped off when the ICM was made. I can't tell
if the ICM was made to be electrically insulated from the
distributor body. When the ICM was hooked up for testing one lead
was connected to the metal base at the bolt hole. Ground? If so
would than mean the ICM is not an electrically insulated design?
When testing, leads were connected to the pickup terminals I guess to
stimulate the ICM, and leads were connected to the terminals for the coil,
I guess to read the ICM output. There is an additional terminal on the ICM
which was left unconnected during the test. the store clerk who did the
test on both ICM's said it was "probably just a ground". The wiring
diagram in my Haynes manual shows it going to the car's computer. Duh.
Makes me wonder about the test. Does it sound reasonable to test the
module without hooking up the computer lead?
the stamped metal base on the ICM is flush around the edge and at
the bolt holes, I assume for structural contact with the
distributor housing it is bolted to, but it is slightly depressed
in the central area leaving an air gap between the ICM and the
distributor. On the distributor from the wrecker there is a clear
(yellowed) paste (like petroleum jelly) where I took the ICM off.
(I have the distributor in front of me on the desk as I type.)
There is evidence of this clear paste all over the base of the ICM
even after I wiped it with a rag to clean it up before taking it
for testing, and squeezed into the bolt holes as well. I assume
its the original ICM and the paste was put on when the car was
made. I tested a drop of the paste off the distributor with an ohm
meter and got no current reading but at the low dry cell voltaage
that may not mean anything.
It looks like the car came new with a di-electric paste but not a
heat transfer paste.
I have a very comprehensive (for me) book on car electronics from the
public library with a chapter on electronic ignition but nothing about
installation and applying paste. I'd like to read as much information as I
can about this situation to avoid the cost of more ICM's ($147 - $291 new
locally), and if possible to improve the weak ignition on the Festiva
which was noted in the Lemon Aid guide to used cars. Its -10 deg F outside
today so it's too cold to work on the car, a good day to stay indoors and
think.
L0nD0t.$t0we11
> The exception are silver-bearing heat
> transfer compounds marketed toward ignorant computer users.
Such ignorant folks as the Intel engineers who designed
the Pentium chips and offer engineering support to OEM's that
use them. Which pretty much sums up the accuracy of
your blathering.
do_not_spam_me
>> It's also false that zinc oxide bearing grease doesn't conduct
>> heat well;
>
> No, but it IS true that it isn't even in the same ballpark
> for heat transfer efficiency as colloidal silver.
What's its efficiency, about 0.1W/cm^2/cm?
Why has grease laced with zinc oxide been used far more than any other
in factory assembled products, and why have auto makers recommended it
for their ignition modules since the 1970s? Virtually nothing else
was available back then, except silicone grease containing nothing
else.
>>Dielectric compound is not _necessarily_ the same thing as heat
>>transfer compound, but in practice it's identical -- silicone oil
>>mixed with zinc oxide powder. The exceptions are silver-bearing
>>heat transfer compounds marketed toward ignorant computer users
>Such ignorant folks as the Intel engineers who designed the
>Pentium chips and offer engineering support to OEM's that use
>them. Which pretty much sums up the accuracy of your blathering
You quoted me out of context, and I was warning against the use of
silver-bearing heatsink grease for auto ignition modules, which
usually have exposed connections with hundreds of volts on them. As
for PC CPUs, nothing more than ordinary heatsink grease is ever
needed.
William R. Watt
heat sink grease they sell. Apparently there are different formulations.
They are not all the same. One computer store guy said the thermal
range is up to 77 deg C then the di-electric property breaks down. Another
store has something else which is "stable" to 200 deg C and "intermittent"
to 300 deg C.
Looking in "Automotive Electronics and Computer Systems" by R N Brady
(2001) at the temperature ranges for electronic sensors the typical high
temperatures are 125, 150, 175 deg C (the 175 is for the EGR sensor. The
enigne coolant max is 130 and the engine oil is 170.) It doesn't give an
operating temperature range for the ignition control module but it's
probably lower than the 175 deg C for the EGR sensor.
I think you have to be careful about which heat silicone-zinc sink grease to
use.
newman...@gmail.com
Do not Spam ME said :if the ICM
inside anything as hot as a distributor.
They guessed, and rightly so, anyone experiecing this issue would think of fuel issues, air issues, rad etc etc first since if you tested ICM at garage...it would be cool and work fine. So why do a recall if no one could identify the problem and save themselves money.
So just cause something is placed in a high heat area, dont assume it is meant to perform there.
Heat transfer grease IS Titanium Oxide Grease, high heat transfer rated @ 200c
Dialetic grease cannot transfer at these high heat ranges nessisary, if you use dieletic grease... you'll burn out your new ICM in likely less than a month or so. Look for that engine dying when engine is hot but starts again when cool
(providing ICM isnt cooked, then engine will never start again)
but if your ICM is on your distributor like mine was, look up how to make a wire harness for remote location of ICM to side engine or fender wall.
There are several helpful how tos outthere and one at ranger station forums, just search remote location to find it.