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Fan clutch issue?


firenexx

Active Member
Joined
May 29, 2010
Messages
25
Vehicle Year
1994
Transmission
Manual
Hey all, I may have a fan clutch issue. I have been scouring the internets reading about all sorts of fan clutch problems on various forums, but I figured I'd post my particular symptoms to make sure I'm not spending money on something that's not an issue.

I'm driving a '94 Mazda B4000 with 166k miles. 5 spd, w/ A/C (But I'm currently bypassing the compressor as it is broken, so no A/C.)

My engine takes a loooong time to warm up. The gauge is pretty much here:
C _^__________ H for a while. I can drive around town for a while or spend 5-10 minutes on the highway before it begins to creep up, and then verrryyy slowly. However, in stop-and-go or sometimes after being on the highway for longer (maybe half an hour or an hour, and especially in hot weather) it begins to overheat. It goes all the way up to the H sometimes, and generally will stay between the middle point and the H. I also see it fluctuate randomly.

I just idled it for about 10 minutes. The fan turned on full blast for the first few minutes as I guess it is supposed to. Afterwards it kinda slowed down and disengaged to the point where I could stop it with a wad of newspaper. I went outside again after about 10-15 mins and the engine had not warmed up to normal temp - it was only slightly above cold on the gauge. At this point I could not stop the fan with a wad of newspaper although it was still slightly slower than the hurricane winds it was putting out at startup.
I also notice about 1/4" to 1/2" of wobble when watching the blades.

I thought at first the temp sender could be bad but I noticed there was coolant coming through the overflow tube after I came off the highway once (after it had gotten pretty hot) so I know it is actually getting pretty hot like the gauge says.

As far as I can tell these are the symptoms of a messed up fan clutch. (Unfortunately I didn't think to check whether or not the fan was on on the highway when overheating. I am going to assume it was not, and I don't plan on doing any more highway driving until I get this fixed but I should probably check.) I recently replaced the thermostat. I haven't replaced either the temperature sensor or the temperature sender but I probably will just to be sure. Does this sound to y'all like it is the fan clutch or should I look elsewhere?

(There is a sufficient amount of coolant and it's been burped.)
 
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You must not have read

Do you know to turn the heater on while filling the radiator? Sounds sorta like you may have some air trapped in there and it isn't completely full of coolant. Did you run the engine and fill the radiator for 10 minutes with the engine up to temp?
The sender is up high and if there is air trapped the sender is in that air.. The reading isn't the same in air as it is in coolant.
After making sure the system is truly full of coolant, if the temp gauge doesn't change for the good then check the sender and the sender connection.
You have indicated the fan clutch to be working as designed.
Is the new thermostat installed upside down?
Big JIm:hottubfun::wub:

Hey all, I may have a fan clutch issue. I have been scouring the internets reading about all sorts of fan clutch problems on various forums, but I figured I'd post my particular symptoms to make sure I'm not spending money on something that's not an issue.

I'm driving a '94 Mazda B4000 with 166k miles. 5 spd, w/ A/C (But I'm currently bypassing the compressor as it is broken, so no A/C.)

My engine takes a loooong time to warm up. The gauge is pretty much here:
C _^__________ H for a while. I can drive around town for a while or spend 5-10 minutes on the highway before it begins to creep up, and then verrryyy slowly. However, in stop-and-go or sometimes after being on the highway for longer (maybe half an hour or an hour, and especially in hot weather) it begins to overheat. It goes all the way up to the H sometimes, and generally will stay between the middle point and the H. I also see it fluctuate randomly.

I just idled it for about 10 minutes. The fan turned on full blast for the first few minutes as I guess it is supposed to. Afterwards it kinda slowed down and disengaged to the point where I could stop it with a wad of newspaper. I went outside again after about 10-15 mins and the engine had not warmed up to normal temp - it was only slightly above cold on the gauge. At this point I could not stop the fan with a wad of newspaper although it was still slightly slower than the hurricane winds it was putting out at startup.
I also notice about 1/4" to 1/2" of wobble when watching the blades.

I thought at first the temp sender could be bad but I noticed there was coolant coming through the overflow tube after I came off the highway once (after it had gotten pretty hot) so I know it is actually getting pretty hot like the gauge says.

As far as I can tell these are the symptoms of a messed up fan clutch. (Unfortunately I didn't think to check whether or not the fan was on on the highway when overheating. I am going to assume it was not, and I don't plan on doing any more highway driving until I get this fixed but I should probably check.) I recently replaced the thermostat. I haven't replaced either the temperature sensor or the temperature sender but I probably will just to be sure. Does this sound to y'all like it is the fan clutch or should I look elsewhere?

(There is a sufficient amount of coolant and it's been burped.)
 
Thanks for the response. I tried burping a few more times (heater on), no success. Coolant level stayed the same.
I tested the sender cold and it read around 380 ohms between the sender and all of the ground spots I tried. According to the manual it is supposed to be 75 at full cold, so I guess this indicates a bad sender.

I may have actually installed the t'stat upside down... I don't mean in reverse, of course, because that would be slightly more stupid. But I don't think I paid attention to where the funny little ball valve thing was and now that I think about it, that's supposed to be pointing up. When I replace the sender I'll rotate the thermostat to its proper position and then burp the system properly. Hopefully that will solve my problems.
 
When you take the thermostat out look closely at it... Somewhere on it should be an ARROW pointing to the radiator.. Showing the intended flow of coolant. This should put the actual thermal part to the hot engine coolant.
Big JIm
 
I should note that I did put it in the correct direction longitudinally. I.E. I didn't install it backwards or reverse. When I say I may have installed it upside-down, I mean that it may be rotated so that the little hole that's supposed to stop air bubbles from being trapped is lower rather than higher, which would not really help to get rid of air bubbles since those would be higher. So while I am 100% sure I installed the thermostat in the correct direction, I may not have rotated it so that the little hole in the flange was in the right spot. Perhaps this could be why there are symptoms of an air bubble yet burping does not release one.

Now that I think back, I may have royally screwed up my radiator a few months back by putting in the dreaded stop leak stuff instead of shelling out the < $100 for an aftermarket radiator like I should have. Maybe that's contributing to the problem.
 
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fan

i also have this problem. i replaced thermostat,radiator, water pump and all hoses. istill get hot with ac on in town driving. any ideas?
 
You should start your own thread.

i also have this problem. i replaced thermostat,radiator, water pump and all hoses. istill get hot with ac on in town driving. any ideas?

When you say HOT.. what does that mean to you? Is it puking it's guts out? are you at hiway speed? We need more information to make a guess.
Big JIm:hottubfun::wub:
 
hot

guage goes 3/4 ths of way to hot and when i kill engine overflow resivoir fills and overflows. only in town driving with ac on . on highway guage runs almost 2/3 to hot.
 
Something is making it hot ain't it? First things first. You describe what happens when there isn't enough coolant in the system. You first need to turn the hater on and fill the radiator with the engine running for 10 minutes or so till the coolant is circulating real good and there is no more air coming out the radiator fill hole.
Many times there is a small outside the engine leak that lowers the coolant level you have posted these symptoms.
hen when driving if the same conditions persist a thermostat may be in order. At the same time the fan clutch should be considered.
Big JIm
 
fan clutch

new clutch solved problem . thanks.
 
Well I replaced the temp. sender and rotated the thermostat about 45 degrees clockwise so that the little air valve thingy was pointing up. I burped the sh*t out of it. Got on the highway - the "undercooling" problem seems to have been fixed (probably the sender) because it got up to normal temp fairly quickly.

After about half an hour though, it got a bit hotter. Perhaps C_____-__H
And when I got back onto city roads (after about 40 minutes) it got REAL hot, about C______-_H. After about 10 minutes of me hoping I wasn't destroying my engine, I arrived at my destination. Popped the hood with the engine still running. From my understanding, at that point the fan definitely should have been engaged. But it was running pretty damn slow (I couldn't even feel a breeze on my hands at all) and had some visible wobble.

I'm bout to order a fan clutch, I'm hoping it's not something else but this seems like it. It seems like the fan was not engaged for most of my highway driving, but then once I got back to city roads it did not increase in velocity like it was supposed to.
 
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