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View Full Version : Real-world driving exp. with a Mark VIII fan.



gmachinz
07-23-2005, 06:31 AM
Since I have not seen anybody post a thread showing results of using one, I thought I'd share my experiences. For starters, I'll explain my system. It consists of a Mark VIII fan, a DC progressive controller (set with the AC lead connected to the AC coil and using the -22 degree jumper), a Northern Racing universal 31x19 radiator, a 180 t-stat and a coolant mix of 20% ethylene glycol antifreeze and 80% distilled water with a bottle of 40-Below cooling additive. The last couple of weeks here in Iowa have been stiffling to say the least. Three days ago the temperature was 100 degrees with the heat index hitting 108 with about 90% humidity. I drove my '78 Monte (355cu, 10.5 comp. 3.73 gears, TH400) for 45 minutes in various parts of the city and country side with the AC blowing of course (stock AC system but with an R134 retro-fit). Speeds where about 35-45mph for the first 20 minutes or so on average and I gave it a good 15 minute run at about 80 mph around some curvy areas north of Des Moines-up and down gradual hills and many straightaways. After cruising through the city for another 20-25 minutes, I headed home. When I pulled into my driveway, my AC was reading 48 degrees at the vents and coolant temperature was just beginning to hit 140. It took a full half hour to go over 100. My amp draw reading from my Mark VIII fan at that point was 27 amps. My experince with a progressive controller is that it does not let the engine spike in temperatures and my Mark VIII is actually overkill for my cooling system but that was the worst weather day in terms of heat and humidity so far this year. Other people may have varying results but with this combination, I don't know that I can design it any better. Anybody else have experiences to share?-Jabin

I just wanted to add that my tranny temp stayed at 135 degrees constant once it reached that temp. after about 30 minutes of driving. I use a custom built electric fan/cooler assembly for that as well.

68protouring454
07-23-2005, 06:46 AM
thats too cold for tranny fluid and your engine oil was probaly not hot enough either to burn all moisture out, you want tranny fluid betwen 160-200 and your oil at 190-220, you should let engine get to 180-90 before having fan come on.
jake

myclone
07-23-2005, 02:41 PM
thats too cold for tranny fluid and your engine oil was probaly not hot enough either to burn all moisture out, you want tranny fluid betwen 160-200 and your oil at 190-220, you should let engine get to 180-90 before having fan come on.
jake

I'll agree with the engine oil temps being too low but the trans temps arent a huge issue. Within reason you can not over cool a slush box especially when high stall TCs, big TQ, heavy car and/or all of those are added. On the other hand most any well maintained auto will live happily in the 160-200 deg range for years if 200 is the max it will see but keep in mind the lower the trans fluid temp is (within reason) the longer the trans will last.

Something else to keep in mind is the location of his trans temp sending unit. If its in the pan or hung out next to the cooler a mile away from the trans what hes seeing isnt a true reading of the internal trans temp where it actually counts. Since its practically impossible to locate the sending unit in the optimum place inside the trans the next best thing is in the hot fluid out line as close to the trans as physically possible.

gmachinz
07-24-2005, 06:18 AM
I'll be pulling the -22 degree jumper out to see what happens with the coolant reading. As for the tranny temp sender, I have it plumbed in my remote filter on the pressure side coming out-approx. 3 feet from the actual transmission itself. So, maybe I'm actually seeing a drop of about 10-15 degrees from what the temp. may actually be. A tranny tech who builds performance autos locally claims an stable temperature of 140 is perfect for a GM TH350 or TH400. -Jabin

pushrod243
07-24-2005, 08:01 AM
Gmachine

If you have a 180 thermostat shouldnt your coolant temp be at least 180. Or am i missing something?

myclone
07-24-2005, 02:23 PM
As for the tranny temp sender, I have it plumbed in my remote filter on the pressure side coming out-approx. 3 feet from the actual transmission itself.

Without seeing your exact set up Id say that location is perfectly fine. Youre prolly within about +/-5 deg so IMO nothing scary will happen without you seeing it on the gauge (nothing scary as far as temps are concerned :scared: )

Blue70
07-24-2005, 04:12 PM
Gmachine

If you have a 180 thermostat shouldnt your coolant temp be at least 180. Or am i missing something?


We both must be missing something :geek:



Oh ya..
You can read my findings on my Mach VIII fan swap HERE (https://www.pro-touring.com/forum/showthread.php?t=8075)



.

gmachinz
07-25-2005, 01:36 PM
I think about that every time I go driving, too! I have the required 180 degree in there. That's why I said I thought either my gauge or sensor was acting weird. My digital temp. probe at the housing reads 177 when my gauge reads 120-so maybe I have an issue to figure out. I have no underhood heat though-which is wierd, espescially on these hot-ass Iowa days we've been having lately. -Jabin