| [GMCnet] What should I also do while radiator is out? [message #279603] |
Thu, 11 June 2015 09:24 |
glwgmc
Messages: 1014
Registered: June 2004
Karma: 10
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Senior Member |
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Hi Tyler,
As I recall the 75 used a “horse collar” type fan shroud that had a rubber piece between the inner and outer sections of the fan shroud. If that is torn or missing it could present symptoms like you describe and it does not fully cover the radiator. You might want to look into a replacement split shroud that covers the whole radiator and positions the fan properly at a location half in and half out of the shroud. If you are using a stock fan I doubt if you would see any significant difference in cooling between the NOS Delco fan clutch and the heavy duty Hayden 2747 (which will be much louder). One “trick” to speed up fan clutch replacement from the top is to loosen the belts so you can manually turn the water pump pulley so you are always working on the nuts from the top side. Use a lever bar about 20” long instead of a screw driver to pull the belts tight when you are through. The water pump is not all that hard to replace if you carefully keep track of how it and the power steering pump are mounted - assuming they are mounted the way the book shows and not screwed up by someone in there before you. If you are still using fender liners you might want to try taking them out to see if that improves your cooling issue. Something is amiss as these things did not overheat when new.
My Clasco ran hot when I brought it back to the west coast from FL. I found the horse collar rubber torn. When I preemptively replaced the engine it squealed belts like crazy when I had the plastic fan and 180 thermostat in place. I tried every combination of fan clutch I could find and nothing worked for me until I put on the stock fan, 195 thermostat, standard duty fan clutch and removed the fender liners. Now it behaves as it should even going up steep grades in hot weather. I, too, got good at changing fan clutches!
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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Message: 1
Date: Wed, 10 Jun 2015 21:15:28 -0600
From: Tyler
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] What should I also do while radiator is out?
Message-ID:
Content-Type: text/plain; charset="utf-8"
Update(s)
When I put the radiator back in (it checked out as re-cored in its past and looked and worked fine) I bought vacuum shutoff for the heater hose to the
rear house water heater. (I checked for, and found the restrictor in the rear block connection for the dash heat and house water heat.) With the rear
loop out, it took less time to get the air out after refill, but still kept temp climbing the harder I worked it.
It was suggested I confirm with infrared. Several test runs showed gauge to be consistent and 180 a tick over 1/4, and 220 at half. IR readings showed
lower hose only about 20 degrees cooler than upper.
I just did not want to do the water pump. I found a receipt for a pump in engine re-build list from 12 years ago, 6000 miles ago. Which doesn't prove
it is good, just that it is not seen a lot of miles.
I checked timing again. Verifying 12 degrees at idle (with vacuum advance unplugged).
I decided to put the Hayden 2747 clutch fan back in, despite having found a Delco NOS. The Delco was very quiet, I liked it - too quiet I have now
decided. the Hayden clutch runs almost literally all the time except for a flat 40 mph cruise. loud. Found a Hayden company flyer that stated it is
designed to come on at 170 degrees, sooooo, it just stays on. Hearing the Hayden run clarifies the Delco was not "roaring" at start up, despite
blowing pretty strong at idle.
With Hayden, about 30 degree difference in upper and lower hoses, 180 at the thermostat housing.
Gauge still climbed to almost half way doing a 62 mph test run. Clearly better than before (AC and 55 mph 3/8 on gauge), but just seems to not be
removing heat. Unless you all have direction, the next question I need to answer is whether to change the water pump. Dick Paterson said he has seen a
handful of engines where the impeller was loose from the shaft and just wouldn't move enough water at speed. I dread the belt adjustment and power
steering pump more than the water pump. I had ordered a water pump and it came with smaller than 4 1/4 water wheel, and went to NAPA today and theirs
was the blade impeller style. Looked like it could throw some water though...
Getting to 40 minute fan clutch replacement from top, removing nothing else! Wish I wasn't getting good at this. Might make 30 or less if had someone
outside to pick up the washers and bolts for me all ten times I dropped them.
--
1975 Glenbrook
Raleigh, NC
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Jerry & Sharon Work
78 Royale
Kerby, OR
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