OVER HEAT ING

[Guest]

I HAVE A 73' BUICK CENTURY FOUR DOOR (350 2BARREL)<BR>THE FOURTH DAY I HAD IT IT OVERHEATED.<BR>REPLACED THE THERMOSTAT AND IT DOESN'T OVERHEAT BUT IT STILL RUNS A LIL HOT.<P>ITS THIS JUST A BUICK PROBLEM?<BR>DID THESE ENGINES JUST RUN HOT?<BR> THANKS FOR ANY HELP...<BR> ARIZONA KID

[Guest]

It shouldn't run hot all the time. The radiator may be partially plugged either externally or internally. The clutch fan might be bad. If you just got it you don't really know how old the parts are. <P>Tomsriv<BR>71 Riv

[Guest]

They don't run hot on the norm. Ya got a prob somewhere. A cheap & quick but not completely accurate test is to get the engine warm, then feel the top of the radiator from one end to the other. If you get any cold spots or uneven temps by feel then have your radiator checked out. Another test which I'm unsure if it works or not, but to test the fan clutch, drive car awhile, turn on a/c and stuff, when ya get home, turn the fan backwards by hand. If it doesn't catch and stop after I think 2-4 turns the clutch is bad. Make sure your fan shroud is in present and complete. Installing a 180* or some even use 160* thermostats can help.<P>Check yer timming, make sure it's correct or within reason +/- 4* or so. Err on the high side. Check plugs, replace if necessary. Check Dwell & Points. Make sure all belts are tight also.<P>That should give ya a good start..<P>Remember, if it's ever overheating, turn the heater on, it helps cool down the engine. But remember don't continue to drive on a hot engine. Bad mojo..<P>Have a 71 350-2, only overheated on me twice. Once due to the a/c being on in 95+ heat in traffic the other was weird, I pulled off the freeway and the light came on out of the blue.<P>Good Luck!<P>-S

[Guest]

Good advise,<BR> The way I do the clutch fan test is a little different. I get the car warm and then pop the hood (So you can see the fan). Turn the car off and see if the fan stops with the engine. If it isn't locking up it will spin for a few seconds.

[Guest]

The 73' century heat beast has a new waterpump, hoses, and a brand new flex fan.<BR> <BR>I suppose maybe a partially cloged radiator....but i mean this thing is on the verge of everheating just idleing!!!<P>(also looking for an oem radio)<BR> <BR> thanks in advance for any advise.

[Guest]

The 73' century heat beast has a new waterpump, hoses, and a brand new flex fan.<BR> <BR>I suppose maybe a partially cloged radiator....but i mean this thing is on the verge of everheating just idleing!!!<P>(also looking for an oem radio)<BR> <BR> thanks in advance for any advise.

[Guest]

This is ones man opinion, but flexfans are BAD. Don't use 'em..<P>Check everything with the above tests. It should give you an idea of where to look first.<P>A proper fan would be a 7 blade stock fan w/clutch. Some cars (small block, no a/c mainly) came with 4 or 5 blade fans.<P>Also, if you've changed the coolant or messed with anything anywhere, make sure to bleed the system or overheating will occur. Air doesn't cool. ;-)<P>Tom, I like your method better. :-) It's unfortunat that I fail both tests and hate having to remove all that stuff to replace the clutch. Not to mention the price of the thing. <P>Cheers!<P>-Scott (in hopes of getting at my engine later today)

[Guest]

Do Flex Fans have clutches?<BR> This fan has no play and stops when the engine stops. I chose not to do the newspaper<BR>test for obvious reasons.<BR> What exactly does the flex fan actually do? The car came with it and this is the first one I've seen.<BR>......and how do fan clutchs work, I mean what do they do exactly.<P> Thanks,<P> Arizona Kid<BR> (shadetree mechanic)

[Guest]

Newspaper test??<P>Flex Fans TMK, have no clutch and just spin. Flex fans from what I hear are razor sharp which have a bit of flex in the blades. Don't quote me on that one, but I do know as I've read it that they are sharp and not like the dull edged stock blades.<P>Clutch Fans taken from my '71 Chassis Manual:<P>"The torque sensitive fan clutch is equipped with a temperature sensitive coil which controls the flow of silicone throuhg the lutch."<P>"During peroids of opperation when radiator discharge air tempurature is low, the fan clutch limits the fan speed to a maximum speed of 1200 RPM."<P>"Operating conditions that produce high radiator discharge air tempuratures cause the tempurature sensitive coil to turn a shaft which opens a port inside the clutch. This open port allows a greater flow of silicone providing a maximum fan speed of approximtely 2600 RPM."<P>"The clutch coil is calibrated so that at road load with an ambient tempurature of approximately 80 degrees F. The clutch is just at the point of shift between high and low fan speed."<P>So, when the incomming air is less then 80*, the fan is limited to 1200rpm, when the temp is higher, the fan is limited to 2600rpm.<P>The common thing is clutch fans, good, flex fans, bad. Cars with L6 & 350 came w/ 4bladed fans unless they had A/C which came with 7 blades. 455's I believe all had 7 blades.<P>Another thing you can try is removing the thermostat and try it that way. Even new thermostats can be bad.<P>Have ya tried the feel test? How did it fare? You can also try bleeding the coolant system again, could be air in the system still.<P>Another suggestion would be to search for the last overheating thread here, it was on a Jeep, but the things to check are still valid.<P>Cheers!<P>-Scott<BR>(a fellow shadetree)

[Guest]

While it would be a good idea to eventually install a 160 degree thermostat, I don't think that is your problem. It could be, but something doesn't sound right to me. It should be checked though.<BR>My dad and I just went thru a similar problem with a 1980 Buick LeSabre. It was air trapped in the system that caused the overheating. The bad thing is it took professional mechanics to resolve, and they admitted they had a tough time fixing it. I don't know if this is something you can take care of yourself. <BR>The fan clutch is what the fan usually bolts to. It's a round disk with 4 holes to bolt up the fan. On the backside, where the fan bolts to, is a shaft that runs thru the center of the fan and ends in a smaller, flat disk that bolts to the water pump pulley. If the fan is just bolted to the pulley, it's not the correct set-up for your car.<BR>A flex fan is supposed to provide cooling at idle, and then provide less air resistence than the stock fan when the car is in motion and the fan is freewheeling. It does this by allowing the blades to bend back a little and allow better air flow over the engine. The problem is that the the blades tend to "freeze" in a set position and provide poor cooling at idle. Also, I've even heard of flex fan blades breaking off and punching a hole in the radiator or doing various other types of underhood damage. This can even happen with OEM used fan blades (after 25+ yrs of use). I recomend you look around the web or Buick dealership for NOS fan blades for your car. I paid $50 for an NOS 7-blade fan for the 455ci BB I'll be dropping into my Skylark...someday.<BR>Definitely check the radiator. It may just need to be "rodded" out. Also make sure the cooling fins on the core aren't filled with junk or bent flat. This would affect cooling too. It might even be the wrong radiator for your car. Radiators have a horizontal row of tubes thru which the water/anti-freeze flows. On top of each row, is another row of tubes running parallel to those. This is repeated almost to the top (and bottom) of the core. So when someone says you need a three row core, they mean the radiator core is 3 tubes deep from the front of the radiator core to the back. I could be wrong, but yours probably came with a 3 row core. If a 4 core radiator is available for your car, give it a try. It will help. <BR>Lastly, if everything checks out ok, you may wish to try a product called Water Wetter. Add it to the distilled water (little/no anti-freeze) in your radiator and it's supposed to do a better job than the usual water and anti-freeze mix at cooling. I've heard nothing but good things about it, and might try it in my Buick when I finish restoring it. You can find it at your local auto stores. Good luck with your problem.<p>[ 05-05-2001: Message edited by: AZ-Skylark ]

[Guest oldtimer]

to check your radiator run car until warm, turn off and feel entire radiator (be carful its still hot)top to bottom. if you feel any changes in temp then you need to remove it and take it to a radiator shop. also make sure you have a STOCK fan shroud and at least a GOOD flex fan (if its not stock). those high performance colored ones with the small blades SUCK, haden (sp?) makes a nice 5-6 blade flex fan in different sizes thats a oem replacement. also if your car has a heater control valve on one of the heater hoses, turn on the heater (just switch it to warm) and run system until warm (with cap off ***BE CAREFUL***) to work out the air in heater core. oh yea, another trick is to drill a small hole in the flat spot of the thermostat if there is any air trapped by the thermostat the hole will let it through.

[Guest]

BUY A GOOD FLEX FAN "HAYDEN" THEY DONT BREAK,THEY STEAL LESS HORSEPOWER AND THEY MOVE MORE AIR. YOU NEED A GOOD SHROUD AND I WOULD RECOMMEND A 180 STAT A 160 WILL NOT HOLD THE COOLANT IN THE RADIATOR LONG ENOUGH TO COOL IT ALSO A CLEAN FOUR ROW RADIATOR. THIS IS HOW I KEPT MY 450 HORSE BIG BLOCK COOL SO IT SHOULD WORK FOR YOU.

[BuickNut]

Bleeding the cooling system of air is not that tough of a problem....I had air trapped in my '86 Ford Ranger system and easily fixed it...I simply jacked up the front of the vehicle so the radiator hose (upper) was the higher than the hose inlet in to the engine, undid the radiator cap, let the vehicle sit for a while and allow the air to bleed out through the stop ball in the thermostate, then filled up the coolant with the car still raised. With todays totally enclosed systems I can't vouch how difficult bleeding would be - but on the older vehicles, its and easy fix and a good practice to follow when you change coolant and/or thermostats.<P>Might also do some background checking on how long the car sat and maintenance on it before you bought it....possiibly worst cast might be your blocks' cooling passages are getting plugged (again, worst case scenario...)<BR>Just my 2 cents worth - good luck.