Fan Clutches and Onan 4k ?s

T

tmaki1

New member
Aug 25, 1999
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1. Fan Clutches:

While doing some parts sleuthing at the local
Cadillac/Olds/GMC dealership in Riverside, I found the
following (among others):

For those contemplating a General Motors solution to a
fan clutch replacement, in the Parts Interchange Index P/N
561826 is still a good GM part number for the original fan
clutch. P/N 12529772 is a good number for the "Olds
diesel" version some have suggested would be a good
replacement. (In the PII, there is not a distinction between
these two.) In my haste during a short lunch hour, I forgot
to write down the price, but it seems that I was told about
$140-ish.

2. Onan ?s

Changed oil in the 4k yesterday. Tried to purchase from
NAPA the oil filter that PO had used, #1339. Was told
that 1339 was not a NAPA number, but showed counter
guy the box top with ID info. He said, "Hmmm." Using PII,
crossed to NAPA 1348 from AC PF-53 as listed in PII.
Okay.

After chaning oil and filter, a new situation got my
attention. Now when Onan runs, the dipstick acts like a
pop-off valve, pulsing up and down to the rhythm of the
pistons. Does it for 15 or 20 seconds, then settles down
for 20 or 30 seconds, and then goes through the cycle
again as long as engine is running. Didn't do that before.
Only difference is the filter. Any ideas out there what could
cause this? I also observed that previously a little blue
smoke came out of the exhaust as long as the engine
was running (obviously, burning a little oil). Now, there is
no blue smoke unless I hit the throttle and rev the engine a
little. Could there be a relationship between these two
phenomena?

3. Oil cooler lines

Spent most of the day yesterday replacing the oil cooler
lines with JR Slaten's works of art. Without getting into the
greasy details, for those who have not yet put on their
Slaten cooler lines, just be aware that when he says
"tighten", TIGHTEN is what he means. They go in like a
breeze, but ya gotta get 'em tight.

Hope the parts info helps, and TIA for any
advice/suggestions on the Onan.

Toby Maki
'73 Glacier 230
 
>
>After chaning oil and filter, a new situation got my
>attention. Now when Onan runs, the dipstick acts like a
>pop-off valve, pulsing up and down to the rhythm of the
>pistons. Does it for 15 or 20 seconds, then settles down
>for 20 or 30 seconds, and then goes through the cycle
>again as long as engine is running. Didn't do that before.
>Only difference is the filter. Any ideas out there what could
>cause this? I also observed that previously a little blue
>smoke came out of the exhaust as long as the engine
>was running (obviously, burning a little oil). Now, there is
>no blue smoke unless I hit the throttle and rev the engine a
>little. Could there be a relationship between these two
>phenomena?

Toby - even though you can get a cross reference on filters,
sometimes the crosses don't really match because some have an
internal check valve and some don't. If you are noticing the
dipstick pulsing I would guess that there is no check valve in the
filter and you are getting some pressure back down into the oil pan.
Actually, I'm not certain whether the Onan uses a check valve in the
filter on not - I'd have to do some research. Perhaps someone else
knows.

If the OEM filter has a check valve it should serve to increase the
oil pressure to the engine and if your new filter doesn't have the
required check valve you are losing some pressure back to the pan and
not getting as much to the engine. Could be a problem. But first
we've got to determine if it should have a check valve in the filter.

Revving the engine would increase the oil pressure and push more oil
past the rings which is what is giving you the blue smoke. Not
having any blue smoke now is not necessarily a good thing -- it just
might mean less oil pressure than you should have.

Most good filter manufacturers have an application manual that has a
section showing the filter specs. IE whether it has a check valve or
not. You should always check this when you are substituting a
different manufacturer's filter.

Emery Stora
77 Kingsley
Santa Fe, NM
 
Thanks Emory.

The check valve thing was actually my first suspicion.

Now to determine check valve/no check valve . . . and
which x-ref is correct for application.

Toby Maki
'73 Glacier 230

Date sent: Sun, 25 Jun 2000 10:59:25 -0600
To: gmcmotorhome
From: "Emery L. Stora"
Subject: Re: GMC: Fan Clutches and Onan 4k ?s
Send reply to: gmcmotorhome

> >
> >After chaning oil and filter, a new situation got my
> >attention. Now when Onan runs, the dipstick acts like a
> >pop-off valve, pulsing up and down to the rhythm of the
> >pistons. Does it for 15 or 20 seconds, then settles down
> >for 20 or 30 seconds, and then goes through the cycle
> >again as long as engine is running. Didn't do that before.
> >Only difference is the filter. Any ideas out there what could
> >cause this? I also observed that previously a little blue
> >smoke came out of the exhaust as long as the engine
> >was running (obviously, burning a little oil). Now, there is
> >no blue smoke unless I hit the throttle and rev the engine a
> >little. Could there be a relationship between these two
> >phenomena?
>
> Toby - even though you can get a cross reference on filters,
> sometimes the crosses don't really match because some have an
> internal check valve and some don't. If you are noticing the
> dipstick pulsing I would guess that there is no check valve in the
> filter and you are getting some pressure back down into the oil pan.
> Actually, I'm not certain whether the Onan uses a check valve in the
> filter on not - I'd have to do some research. Perhaps someone else
> knows.
>
> If the OEM filter has a check valve it should serve to increase the
> oil pressure to the engine and if your new filter doesn't have the
> required check valve you are losing some pressure back to the pan and
> not getting as much to the engine. Could be a problem. But first
> we've got to determine if it should have a check valve in the filter.
>
> Revving the engine would increase the oil pressure and push more oil
> past the rings which is what is giving you the blue smoke. Not
> having any blue smoke now is not necessarily a good thing -- it just
> might mean less oil pressure than you should have.
>
> Most good filter manufacturers have an application manual that has a
> section showing the filter specs. IE whether it has a check valve or
> not. You should always check this when you are substituting a
> different manufacturer's filter.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM
>
 
The Onan filter has the check valve, and you can buy those from Mr.c for $7
now... The check valve is so that in cold wether then the oil is thick, the
oil can bypass the filter. I would not think it would come into play now
but who knows.

>Thanks Emory.
>
>The check valve thing was actually my first suspicion.
>
>Now to determine check valve/no check valve . . . and
>which x-ref is correct for application.
>
>
>
>Toby Maki
>'73 Glacier 230
>
>
>
>Date sent: Sun, 25 Jun 2000 10:59:25 -0600
>To: gmcmotorhome
>From: "Emery L. Stora"
>Subject: Re: GMC: Fan Clutches and Onan 4k ?s
>Send reply to: gmcmotorhome
>
>> >
>> >After chaning oil and filter, a new situation got my
>> >attention. Now when Onan runs, the dipstick acts like a
>> >pop-off valve, pulsing up and down to the rhythm of the
>> >pistons. Does it for 15 or 20 seconds, then settles down
>> >for 20 or 30 seconds, and then goes through the cycle
>> >again as long as engine is running. Didn't do that before.
>> >Only difference is the filter. Any ideas out there what could
>> >cause this? I also observed that previously a little blue
>> >smoke came out of the exhaust as long as the engine
>> >was running (obviously, burning a little oil). Now, there is
>> >no blue smoke unless I hit the throttle and rev the engine a
>> >little. Could there be a relationship between these two
>> >phenomena?
>>
>> Toby - even though you can get a cross reference on filters,
>> sometimes the crosses don't really match because some have an
>> internal check valve and some don't. If you are noticing the
>> dipstick pulsing I would guess that there is no check valve in the
>> filter and you are getting some pressure back down into the oil pan.
>> Actually, I'm not certain whether the Onan uses a check valve in the
>> filter on not - I'd have to do some research. Perhaps someone else
>> knows.
>>
>> If the OEM filter has a check valve it should serve to increase the
>> oil pressure to the engine and if your new filter doesn't have the
>> required check valve you are losing some pressure back to the pan and
>> not getting as much to the engine. Could be a problem. But first
>> we've got to determine if it should have a check valve in the filter.
>>
>> Revving the engine would increase the oil pressure and push more oil
>> past the rings which is what is giving you the blue smoke. Not
>> having any blue smoke now is not necessarily a good thing -- it just
>> might mean less oil pressure than you should have.
>>
>> Most good filter manufacturers have an application manual that has a
>> section showing the filter specs. IE whether it has a check valve or
>> not. You should always check this when you are substituting a
>> different manufacturer's filter.
>>
>> Emery Stora
>> 77 Kingsley
>> Santa Fe, NM
>>
>
>
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/
 
Thanks Gene.

That's the info needed. Goes into notes . . .

For the record, the NAPA 1348, x-ref AC-PF53, is not the
filter to use for Onan 4k.

Thanks again.

TM

Date sent: Sun, 25 Jun 2000 10:34:09 -0700
To: gmcmotorhome
From: gene
Subject: Re: GMC: Fan Clutches and Onan 4k ?s
Send reply to: gmcmotorhome

> The Onan filter has the check valve, and you can buy those from Mr.c for $7
> now... The check valve is so that in cold wether then the oil is thick, the
> oil can bypass the filter. I would not think it would come into play now
> but who knows.
>
>

> >Thanks Emory.
> >
> >The check valve thing was actually my first suspicion.
> >
> >Now to determine check valve/no check valve . . . and
> >which x-ref is correct for application.
> >
> >
> >
> >Toby Maki
> >'73 Glacier 230
> >
> >
> >
> >Date sent: Sun, 25 Jun 2000 10:59:25 -0600
> >To: gmcmotorhome
> >From: "Emery L. Stora"
> >Subject: Re: GMC: Fan Clutches and Onan 4k ?s
> >Send reply to: gmcmotorhome
> >
> >> >
> >> >After chaning oil and filter, a new situation got my
> >> >attention. Now when Onan runs, the dipstick acts like a
> >> >pop-off valve, pulsing up and down to the rhythm of the
> >> >pistons. Does it for 15 or 20 seconds, then settles down
> >> >for 20 or 30 seconds, and then goes through the cycle
> >> >again as long as engine is running. Didn't do that before.
> >> >Only difference is the filter. Any ideas out there what could
> >> >cause this? I also observed that previously a little blue
> >> >smoke came out of the exhaust as long as the engine
> >> >was running (obviously, burning a little oil). Now, there is
> >> >no blue smoke unless I hit the throttle and rev the engine a
> >> >little. Could there be a relationship between these two
> >> >phenomena?
> >>
> >> Toby - even though you can get a cross reference on filters,
> >> sometimes the crosses don't really match because some have an
> >> internal check valve and some don't. If you are noticing the
> >> dipstick pulsing I would guess that there is no check valve in the
> >> filter and you are getting some pressure back down into the oil pan.
> >> Actually, I'm not certain whether the Onan uses a check valve in the
> >> filter on not - I'd have to do some research. Perhaps someone else
> >> knows.
> >>
> >> If the OEM filter has a check valve it should serve to increase the
> >> oil pressure to the engine and if your new filter doesn't have the
> >> required check valve you are losing some pressure back to the pan and
> >> not getting as much to the engine. Could be a problem. But first
> >> we've got to determine if it should have a check valve in the filter.
> >>
> >> Revving the engine would increase the oil pressure and push more oil
> >> past the rings which is what is giving you the blue smoke. Not
> >> having any blue smoke now is not necessarily a good thing -- it just
> >> might mean less oil pressure than you should have.
> >>
> >> Most good filter manufacturers have an application manual that has a
> >> section showing the filter specs. IE whether it has a check valve or
> >> not. You should always check this when you are substituting a
> >> different manufacturer's filter.
> >>
> >> Emery Stora
> >> 77 Kingsley
> >> Santa Fe, NM
> >>
> >
> >
> >
> Genef -- 77PB/ore/ca
> GMC MOTORHOME INFORMATION
> mr.erf
> http://www.california.com/~eagle/
>
 
I remember that discussion, but I thought the Onan only had the bypass one ??

gene

>>The Onan filter has the check valve, and you can buy those from Mr.c for $7
>>now... The check valve is so that in cold wether then the oil is thick, the
>>oil can bypass the filter. I would not think it would come into play now
>>but who knows.
>
>Gene - some possible confusion here. Oil filters often have two
>valves. You are referring to the bypass valve which allows the oil
>to bypass the filter when the filter gets clogged or, as you point
>out, when the oil is cold and builds too much pressure up.
>
>Filters also often have what I called a check valve, sometimes called
>an antidrainback valve. This keeps the oil from draining back out of
>the filter and keeps a full filter so there is oil flow when the
>engine first fires up.
>
>Here is a site that discusses filters:
>http://members.xoom.com/minimopar/techdata.html
>
>There is also info on this site that discusses someones study where
>they bought many different brands and cut them open to analyze the
>quality of the different brands.
>
>Emery Stora
>77 Kingsley
>Santa Fe, NM
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/
 
>The Onan filter has the check valve, and you can buy those from Mr.c for $7
>now... The check valve is so that in cold wether then the oil is thick, the
>oil can bypass the filter. I would not think it would come into play now
>but who knows.

Gene - some possible confusion here. Oil filters often have two
valves. You are referring to the bypass valve which allows the oil
to bypass the filter when the filter gets clogged or, as you point
out, when the oil is cold and builds too much pressure up.

Filters also often have what I called a check valve, sometimes called
an antidrainback valve. This keeps the oil from draining back out of
the filter and keeps a full filter so there is oil flow when the
engine first fires up.

Here is a site that discusses filters:
http://members.xoom.com/minimopar/techdata.html

There is also info on this site that discusses someones study where
they bought many different brands and cut them open to analyze the
quality of the different brands.

Emery Stora
77 Kingsley
Santa Fe, NM
 
>I remember that discussion, but I thought the Onan only had the bypass one ??
>
>gene

I don't know. That's why I was hoping someone might have that answer.

Emery
 
>Thanks Emory.
>
>The check valve thing was actually my first suspicion.
>
>Now to determine check valve/no check valve . . . and
>which x-ref is correct for application.
>
>

IMHO: I doubt that if a filter without a check valve ( bypass )
would cause the problem you are discribing. the bypass valve is
for bypassing oil in the event, that the filter is too clogged
or too cold and causing a lack of oil flow. this insures that you don,t
run the engine with no oil pressure. there is a low oil pressure
switch on some models as well.

The pulsing MAY be a sign of stuck,broken or very worn piston
rings. OR the wrong grade of oil. are you using SAE 30 oil
or 10-30 ? this also could be the cause of the blue exhaust
smoke. I have the Onan Emerald 4K and it requires SAE 30 only.

John Szalay
73 GMC " Blue Yonder"
 
Yup, Castrol straight 30W. As I mentioned, the _only_
difference was the filter. Running engine just a few
minutes before to warm everything up did not exhibit
pulsing dipstick.

Didn't really have to change oil. Probably didn't have 15
hours on it. Still pretty transparent when drained. Just did
it because I had the stuff handy and was doing mh engine.

Kind of odd that the pulsing cycles, although usual
suspect of pressure being cyclicly relieved would explain
it, I guess. When I hold dipstick in place, I feel no build-up
of pressure, though. Letting go, no excessive expulsion of
built-up pressure.

Hmmm . . .

Toby Maki
'73 Glacier 230
Date sent: Sun, 25 Jun 2000 15:29:21 -0400
To: gmcmotorhome
From: John Szalay
Subject: Re: GMC: Fan Clutches and Onan 4k ?s
Send reply to: gmcmotorhome

> >The check valve thing was actually my first suspicion.
> >
> >Now to determine check valve/no check valve . . . and
> >which x-ref is correct for application.
> >
> >
>
> IMHO: I doubt that if a filter without a check valve ( bypass )
> would cause the problem you are discribing. the bypass valve is
> for bypassing oil in the event, that the filter is too clogged
> or too cold and causing a lack of oil flow. this insures that you don,t
> run the engine with no oil pressure. there is a low oil pressure
> switch on some models as well.
>
> The pulsing MAY be a sign of stuck,broken or very worn piston
> rings. OR the wrong grade of oil. are you using SAE 30 oil
> or 10-30 ? this also could be the cause of the blue exhaust
> smoke. I have the Onan Emerald 4K and it requires SAE 30 only.
>
> John Szalay
> 73 GMC " Blue Yonder"
>
 
Thanks Rick.

The reed valve breather was my second suspicion. In
investigating the blue smoke (hoping it might be traced to
something other than a cause requiring engine overhaul),
I'd read in the t-shooting table about the breather. I'll
certainly check into it. (Thought about it Saturday, but after
spending nearly six hours changing the oil cooler lines
and doing other stuff, I was too dirty, and too tired to tear
something else apart).

Toby Maki
'73 Glacier 230

From: RickStapls
Date sent: Mon, 26 Jun 2000 01:25:03 EDT
Subject: Re: GMC: Fan Clutches and Onan 4k ?s
To: gmcmotorhome
Send reply to: gmcmotorhome

> In a message dated 6/25/00 12:04:08 PM Mountain Daylight Time,

>
> > Oil filters often have two
> > valves. You are referring to the bypass valve which allows the oil
> > to bypass the filter when the filter gets clogged or, as you point
> > out, when the oil is cold and builds too much pressure up.
> >
> > Filters also often have what I called a check valve, sometimes called
> > an antidrainback valve. This keeps the oil from draining back out of
> > the filter and keeps a full filter so there is oil flow when the
> > engine first fires up.
> >
>
> Emery, Gene, and Toby,
> Right you are on the check vs. bypass valves. However..... once the
> engine is running and oil is circulating, the check valve has no affect on
> oil pressure OR crankcase pressure. The bypass valve, if present, may
> prevent excessively high oil pressure due to a clogged element WITHIN the
> filter (and consequently low pressure in the rest of the lubrication system),
> but it has no affect on crankcase pressure.
> When you think about it, nothing in the lubrication system could affect
> crankcase pressure, as the entire lube system, including relief valve, bypass
> valve , intake passage, etc, is ALL contained within the crankcase, so
> whatever goes on goes on internally. Only the introduction of liquid or
> vapor (ie: "blowby") from outside the crankcase can pressurize it.
> Of course it is normal for a substantial amount of blowby gasses to slip
> past the rings (and sometimes the exhaust valve guides) into the crankcase.
> In the old days a vent tube released these fumes to the air. Since this
> accounted for about 30% of the pollution emitted in the OLD days, the very
> first emission control involved adopting the PCV ("positive crankcase
> ventilation") valve which Willys invented (I think) to allow waterproofing
> the Jeep's crankcase. (I'm speculating here, but I know the military used to
> waterproof their vehicles, and the earliest PCV valve I ever saw was on a
> 1948 Jeep CJ2A.) Whatever its origins, the PCV valve, or some variant
> thereof, was adopted for the 1963 model year, beginning the whole emissions
> control process.
> The Onan was apparently include in the emissions equation, or perhaps they
> just found that the PCV system was actually good for keeping the crankcase
> clean, especially on an engine that runs flat-out standing still much of the
> time. The Onan uses a reed check valve within the top of the crankcase,
> leading to a rubber hose which directs the vapors to the carburetor inlet
> duct to be burned up. Both the check valve and the hose occasionally get
> clogged up or stuck shut, causing excessive pressure in the crankcase. This
> in turn leads to oil leaks AND excessive oil-burning (blue smoke). Your
> dipstick's strange behavior seems to confirm the problem.
> Check and clean your crankcase vent system and I think the smoke etc. will
> diminish. See section 24C, Figure 31 (page 24C-22 in my copy) of your GMC
> Maintennance Manual (X-7525B) for details.
>
> My .02. HTH.
>
> Rick Staples
> '75 Eleganza
> Louisville, CO
>
>
 
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