| [GMCnet] Curiosity question [message #281499] |
Sun, 05 July 2015 11:57  |
glwgmc
Messages: 1014
Registered: June 2004
Karma: 10
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I have followed only casually all this discussion about oil flow, etc. but it does raise a curiosity question for me. Why would anyone go to all the trouble and expense to replace an engine in a GMC motorhome and not also replace everything that touched water, oil or which moves? If you do, why do you care whether the oil can or cannot bypass the oil filter under some assumed set of circumstances? A new radiator, whether aluminum or brass, costs less than $1000. If you want to keep your existing radiator for some reason, an external fan assisted oil cooler costs less than $300. A quality remanufactured long block will cost from $2000 to $10,000 and the R & R will cost between $2000 and $5000 (or take somewhere around 25 hours if you do it yourself) so why take a chance with reusing old components no matter where or how the oil flows? Inquiring minds would like to know……..
General Motors built a ton of these Generation 2 engines so had a lot of warrantee experience to draw on when it came to lubrication under all sorts of use so it seems unlikely to me that we could really learn much of use by trying to set up some sort of an experiment to try to out engineer them now. My take on it anyway.
A really compelling answer to all these questions would be the same one a friend once gave me when I asked him how he could justify the new Lear Jet he had just purchased. He replied, “because I can afford it and I want one”. Hearing that I cleverly changed the subject…...
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
glwork@mac.com
http://jerrywork.com
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Jerry & Sharon Work
78 Royale
Kerby, OR
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| Re: [GMCnet] Curiosity question [message #281508 is a reply to message #281499] |
Sun, 05 July 2015 15:39  |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Jerry,
I comprehend what you have noted below and while I cannot afford a Lear Jet I can afford to "replace everything that touched water,
oil or which moves."
I watched the video about the Hot Flush system on Jay Leno's garage and it impressed me so much I watched it over and over until I
had gleaned every shred of information from it I could.
I then sent the following information in to GMCnet last week as part of a long email without the step numbers separated by blank
lines and it got bunched up and I suspect people did not catch all the comments made during the video.
If you have not done so please watch the Hot Flush video on Jay Leno's garage;
http://www.hotflusher.com/automotive/Jay-Leno-Hot-Flush.cfm
Please pay particular attention to the following comments (especially No. 4):
No. 1) @ 1:05 minutes - Automatic Transmission Fluid is used because it has detergents and carries contamination well
No. 2) @ 1:30 minutes - Oil cooler acts like a filter
No. 3) @ 2:10 minutes - Forty (40) year old Lotus cooler - hmmm 40 year old GMC
No. 4) @ 2:20 minutes - Second hand cooler cleaned is just as good as a new one if you can flush it out
No. 5) @ 3:13 minutes - Fluid is heated to 193°F which is normal operating temp
No. 6) @ 3:27 minutes - Cooler expands a bit from the heat and gets cleaned better
No. 7) @ 4:40 minutes - Note how flow reverses with a hard pulse
No. 8) @ 5:12 minutes - Note flow reversing on flow meter
No 9) @ 7:15 minutes - Note that the filter you check is 28 microns and the main filter is 10 micron
As far as I'm concerned cleaning the OEM engine oil cooler or transmission fluid cooler in a GMC radiator is tantamount to replacing
it with a new one.
In another email I noted the following:
I noticed there are 80 + testimonials on the Hot Flush website so for the hell of it I called A-1 Transmission in Kerrville, TX and
the owner said if I brought the GMC radiator into his shop he would clean both the engine and transmission coolers for $95.66. He
said he normally charges $95.66 each but would do both for the same price since I was bringing in the radiator.
As noted in my first sentence I can afford to replace everything but after careful evaluation of the information above I choose to
spend $95.66 to clean the coolers rather than buying a new radiator for "less than $1000." I would, however, replace the OEM rubber
oil cooler lines with a set of JR Slaten's Teflon lined braided stainless steel lines. I'll put the money I save towards a Lear
Jet. ;-)
As far as installing an external fan assisted oil cooler goes please note that the GMC engineers could have done that, however, they
chose to install the oil cooler in the radiator. I believe they did that is because the temperature of the oil could be better
controlled and kept in a tighter range. The temperature of the oil returned to the engine will track the water temperature very
closely because a liquid to liquid oil cooler is far more efficient than an air to oil cooler. I realize that high quality oil
coolers have thermostats and switches that control the temperature of the oil by bypassing the flow until the oil reaches the
desired temperature and turning the fan on and off to keep it below the max temp. I understand the motivation for installing a fan
assisted oil cooler from the viewpoint of assuring that contamination from the OEM radiator engine oil cooler does not return to the
engine, however, I HOPE I have convinced everyone that oil from the cooler must flow through the oil filter to get back into the
engine. If someone decides to install a fan assisted remote oil cooler I would suggest they install a gage to monitor the
temperature of the oil returning to the engine. If you're out in Arizona in the middle of summer and the fan on the oil cooler fails
I'll bet dollars to donuts that the return oil temp is going to go through the roof! Yes I know it has been noted by several people
that they don't have a oil cooler and so far so good. It would be interesting for one of those people to install a temperature gage
in the oil filter adapter to see how hot the oil coming from the engine is getting.
As far as the experiment goes the engines (455 or 403) in our GMC's came from the Oldsmobile Toronado. The Toronado did not have an
engine oil cooler; the oil filter attached directly to the oil filter base. According to MM X-7525 the bypass valve in the oil
filter base is set to open at 5.3 to 6.3 psi. I have been told that the oil filter base in the Toronado is the same as the GMC. I
have not been able verify that in any GM documentation. I don't know if the 5.3 to 6.3 psi takes into consideration the oil cooler
adapter, lines to the radiator oil cooler, oil cooler, lines back to the oil cooler adapter, and the oil cooler adapter or not.
Those additional components would increase the pressure drop across the bypass valve. The test Tom Pryor is going to conduct is to
determine if the additional pressure drop created by those components causes the bypass valve to remain open and allow oil to bypass
them under normal operating conditions allowing unfiltered and uncooled oil back into the engine. I define normal operating
conditions as engine RPM from idle to 3600 rpm with a new oil filter, clean lines to and from a clean OEM radiator engine oil
cooler.
Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: Gerald Work
I have followed only casually all this discussion about oil flow, etc. but it does raise a curiosity question for me. Why would
anyone go to all the trouble and expense to replace an engine in a GMC motorhome and not also replace everything that touched water,
oil or which moves? If you do, why do you care whether the oil can or cannot bypass the oil filter under some assumed set of
circumstances? A new radiator, whether aluminum or brass, costs less than $1000. If you want to keep your existing radiator for
some reason, an external fan assisted oil cooler costs less than $300. A quality remanufactured long block will cost from $2000 to
$10,000 and the R & R will cost between $2000 and $5000 (or take somewhere around 25 hours if you do it yourself) so why take a
chance with reusing old components no matter where or how the oil flows? Inquiring minds would like to know
..
General Motors built a ton of these Generation 2 engines so had a lot of warrantee experience to draw on when it came to lubrication
under all sorts of use so it seems unlikely to me that we could really learn much of use by trying to set up some sort of an
experiment to try to out engineer them now. My take on it anyway.
A really compelling answer to all these questions would be the same one a friend once gave me when I asked him how he could justify
the new Lear Jet he had just purchased. He replied, because I can afford it and I want one. Hearing that I cleverly changed the
subject
...
Jerry
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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