Fan Clutch or Not...???

[007]

Here's the background...

My Jeep, in hot weather, would run fine for about 20-40 minutes and at that point, regardless of speed it would start to get hot. This thing had sat for a few years so I took it to a radiator guy well known here locally and they flushed the engine, bypassed the heater (at my request, no top) and flushed and boiled out the radiator, new thermostat and put it all back together.

I went to drive it home and all was well, normal operating temperature then it suddenly got hotter than it's ever been and began blowing water out the over flow. I was just a couple blocks from my home so I let it cool and limped on home, garaged it for the winter and called them back.

They felt like it was possible something else came loose and re-clogged the radiator and they offered to re-do it all for no charge.

So today I towed it in there and we discussed it some more and while driving home I got to thinking "ya know this would be a good time to replace water pump and hoses, fan clutch, etc." So I'm going to have him drain it out, keep the radiator, flush the motor and then I'll tow it home and replace the water pump (they don't do that work there normally) then bring it back when the radiator is done again.

My question is, the AMC 304 's are known to run a little warm - is there any advantage to a fan clutch? Why not just put a spacer in there and bolt the fan to the water pump and let it pull air all the time? My only problem would be perhaps it would be hard to warm up, but that's not really a problem if you don't have a top or heater is it?

Advice please...

 

[lutry]

I would take an infrared-thermometer and check the temperature
of all hoses, the radiator at inlet and outlet and so on to see where
the failure is before taking everything apart, maybe you can localize
it and get an idea what is wrong.

 

[Posi]

Do you have a fan shroud installed?

 

[007]

Do you have a fan shroud installed?

Yes - I do...

 

[Hedgehog]

My question is, the 304's are known to run a little warm - is there any advantage to a fan clutch? Why not just put a spacer in there and bolt the fan to the water pump and let it pull air all the time? My only problem would be perhaps it would be hard to warm up, but that's not really a problem if you don't have a top or heater is it?

Advice please...

Either run with a fan clutch or one of those flexible fans.

Why? When traveling down the road there actually is far more air attempting to pas through your radiator than the fan can move. The clutch allows the fan to turn faster than the motor is running. Without the clutch the fan acts as a barrier.

The flex fan tends o flatten getting out of the way allowing a full flow of air.

 

[ThisGuyUKnow]

ditch the clutch fan and go with dual contour fans and a quality fan controller (i recommend the flexalite variable speed controller). The amount of air they move is well beyond what your clutch fan can do.

 

[GatorBate]

ditch the clutch fan and go with dual contour fans and a quality fan controller (i recommend the flexalite variable speed controller). The amount of air they move is well beyond what your clutch fan can do.

I'm with ThisGuy. Go electric. At low rpm (1000 to 2000) my AMC 304 was constantly over heating on hot days. The electric fan will run full speed if needed no matter what the engine rpm is. You will need a larger alternator to run the fans though.(Delco 12si)

I don't want to start an argument over which is better, electric Vs mechanical. They both have their advantages. But on hot days when I'm idling around between 1000 to 2000 rpm and I notice the temperature gauge starting to climb the fans kick into high speed the temp drops and all is well.

 

[Blazerstud]

i myself had the same prob, until I installed the electric fans. all is well now!

 

[mstar]

You have other fish to fry before you go of on a witch hunt replacing parts with no direction.To me that is not the protocol I would fellow.
Is it reasonable to assume that a stock AMC 304 should operate within normal
limits if everything is working properly.Not saying a flex-fan or electric fan
is a bad idea but lets get to the cause of the problem first.I would start by finding a new radiator shop and do some research on the function of a clutch fan and a flex fan .A second opinion if you will. mike

 

[007]

You have other fish to fry before you go of on a witch hunt replacing parts with no direction.To me that is not the protocol I would fellow.
Is it reasonable to assume that a stock 304 should operate within normal
limits if everything is working properly.Not saying a flex-fan or electric fan
is a bad idea but lets get to the cause of the problem first.I would start by finding a new radiator shop and do some research on the function of a clutch fan and a flex fan .A second opinion if you will. mike

I appreciate your thoughts... The radiator shop is one we use here at work. One division of where I work has 90 KW's and Peterbilts running flatbeds and we have all our work done at this place and I/we trust him. He's also standing by his work by re-doing it for no charge just to make sure. I do feel like something has let loose in there due to increased flow and re-plugged the radiator, but time will tell.

I think once he's done I'm going to go ahead and replace the water pump as it certainly appears OE and is <$50 to do with a new one. I think the idea of taking temperatures at different places is a good idea as well if the problem persists. I also think that after much reading that my best fan option - at this point - is a new clutched fan, again - if the problem persists. I think electric fans are definitely a good solution, and one that's on my radar, but a good working stock radiator/pump/hoses/fan/fan-clutch/engine should work fine for years.

 

[JR74CJ5]

'm here in CA, have a flex fan, and no shroud. Idle crawling in 100 degree temp will still not cause my AMC 304 to over heat...

It does take a bit to warm up on cold mornings, but once it does, its good to go.

 

[IOPort51]

You have other fish to fry before you go of on a witch hunt replacing parts with no direction.To me that is not the protocol I would fellow.
Is it reasonable to assume that a stock 304 should operate within normal
limits if everything is working properly.Not saying a flex-fan or electric fan
is a bad idea but lets get to the cause of the problem first.I would start by finding a new radiator shop and do some research on the function of a clutch fan and a flex fan .A second opinion if you will. mike

The voice of reason raises its head once again.

I am a fan of electric fans, quiet, faster warm up, less HP load. But I will say that even with two 10" electric fans I can become warmer than I would like on a long (mile or so) low gear climb. Something like you are going to find a lot of in the San Juans. I don't know why the digital thermometer never occurred to me but that sounds like a great idea. I suspect that I have an air pocket that I still have not bled out. The heater hose to the manifold seems like a good possibility for me. I have had problems getting the air out before and just when I got the air out I decided to change to a larger redieator and had to start the bleed process all over again. I think you just need to look for hot spots on the hoses as steam is hotter than water.

 

[007]

Quick update on this. The engine blew out some gunk and replugged the radiator. He's reflushing it at no charge.


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[Lumpy Grits]

Do a 'rod-out' on your rad. Have your block pro flushed.
Use only distilled water to mix with a'freeze. NEVER tap water.
Keep the stock fan and fan clutch. They were OEM for a reason
LG

 

[Hedgehog]

Good advice. A radiator shop flush is not the same as home flush. The shop uses far more aggressive chemicals and clean more completely. It can be expensive, but when your engine is shedding gunk into your radiator a professional flush would be a wise move.

 

[007]

That's exactly where it is and that's what he's doing. The block is full of something that's supposed to soak before the reflush. Should be like new when done.


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[Turbogus]

I was having similar issues with overheating and took the project step by step including replacing the radiator with a new 3 row brass/sopper radiator (for free to me from a friend), FlowKooler water pump, new springs (coiled wires) in both upper and lower radiator hoses, fresh 50/50 Prestone and distilled water and just as I was about to give up I found information about the Ford Contour/Merc Mystique fan swap.

When I first got 'BB' she had a pusher fan crammed between the grille and the radiator. I reversed it and turned it into a puller fan, added a shroud and a FlowKooler water pump. Mechanical temp gauge came later along with a better fan controller. Well during the hottest summer days she was running a little too warm for my taste. So I received many reccomendations about switching to the double fan Contour setup. Hit my local boneyard and found one the was already pulled, laying in the trunk of a '98 Merc Mystique (I hope I didn't raid someones cache).



Then began my search for the high speed and low speed relays. First approaching the local NAPA I explained that I needed at least a 70/80 amp relay. Their response was a blank stare followed by thier response "we have relays". Okayyyyy how about 70/80 amp relays. They didn't know. So I went to the Ford dealer in town and gave them the rundown on the vehicle this fan same from; '98 Merc Mystique 2.5L V6 with A/C needed a 70/80 amp cooling fan relay. The same blank stare ensued. After about 10 minutes of tippy tapping on his computer he said he found one that might work but he couldn't find any amperage information, number of pins or their assignment, remarking that this '98 is obsolete !
Had I shown this kind of ineptitude while I was in my MOS would've been changed (and there were some lame brains who were) from truck driver/MTC to 0311 infantry in a heartbeat.
Now, being a former Marine I now about obsolescence, for my first two years I was stationed at MCLB Barstow where, when an old jeep, truck or tank arrived at the rail dock, job #1 was to send a bunch of privates with rattle cans of olive drab to paint out the white star.
Disgusted I returned to the boneyard and pulled some wiring and found these two relays;

Well,I finally pulled the radiator out (good thing I did, one of the mounting flanges was loose) and after removing the stock fan shroud with the small 18" Flex a lite fan I set the Merc Mystique assembly inbetween the tanks and all I had to trim was the top mounting tab.



For controllers, I ended up using a Ford PDB out of a mid 90's truck, for the relays



and isolated the rail mounted on the side,



took my trusty Dremel and ground clearance for the larger footprint 70 amp relay



and used this nasty smelling Devco epoxy that dries harder than the plastic itself. I accidentely broke a corner out of the main PDB and maing a form with blue plumbers tape packed this Devco in and after letting set overnight took 20 minutes with a titanium bit in the Dremel to grind off the flashing. I essentially used the diagram below for my wiring.



Got it wired so far as the dash and when wiring the three way override switch I failed to touch the case to ground so got a failure, it wasn't until I got to work and thought about it and felt those donkey ears spring up. In the meantime I soldered in the diode between the Override and the Control circuit.





Got the switch wired in and as it turns out didn't need to be grounded to function, it was the inclusion of that diode.
I got the switch mounted and am underway cleaning up my underhood electrics with that negative bus bar and the Ford PDB, It's going well and lucky I got into it found my primary wire to the starter solenoid coming loose from the connector. Broke out my trusty hobby vise that I hadn't used in four decades and crushed the connector onto the wire.

After a long drive (100 miles +/-) involving highways speeds, upgrades, bumpy dirt and gravel roads at speed. 'Black Betty' never got above 190* and, if I switched to Override she cooled down to 160*!

Using this system for the past 9 months and I've had no failures despite extended driving over last winters washboard cut into the ice on my commute by trucks running LaGrande tire chains. (Can't say the same for my radio and ignition switch, they both rattled loose breaking continuity)
​

 

[JR74CJ5]

Great post bud, but most of the pictures are not showing up for me. Might be just me...

Looks like they're hosted on another site that requires log in to view.

 

[007]

Yeah I don't see the pictures either, and I wish I did because the electronics of this is the ONLY thing that scares me.

I got mine back and the block is clean and the radiator is good to go, new water pump and fan clutch and hoses. The stock setup "should" keep a stock engine cool, if it doesn't there's a problem somewhere.

Now just want some warm weather to test...

 

[Turbogus]

I'm trying reposting...

I was having similar issues with overheating and took the project step by step including replacing the radiator with a new 3 row brass/sopper radiator (for free to me from a friend), FlowKooler water pump, new springs (coiled wires) in both upper and lower radiator hoses, fresh 50/50 Prestone and distilled water and just as I was about to give up I found information about the Ford Contour/Merc Mystique fan swap.

When I first got 'BB' she had a pusher fan crammed between the grille and the radiator. I reversed it and turned it into a puller fan, added a shroud and a FlowKooler water pump. Mechanical temp gauge came later along with a better fan controller. Well during the hottest summer days she was running a little too warm for my taste. So I received many reccomendations about switching to the double fan Contour setup. Hit my local boneyard and found one the was already pulled, laying in the trunk of a '98 Merc Mystique (I hope I didn't raid someones cache).


Then began my search for the high speed and low speed relays. First approaching the local NAPA I explained that I needed at least a 70/80 amp relay. Their response was a blank stare followed by thier response "we have relays". Okayyyyy how about 70/80 amp relays. They didn't know. So I went to the Ford dealer in town and gave them the rundown on the vehicle this fan same from; '98 Merc Mystique 2.5L V6 with A/C needed a 70/80 amp cooling fan relay. The same blank stare ensued. After about 10 minutes of tippy tapping on his computer he said he found one that might work but he couldn't find any amperage information, number of pins or their assignment, remarking that this '98 is obsolete !
Had I shown this kind of ineptitude while I was in my MOS would've been changed (and there were some lame brains who were) from truck driver/MTC to 0311 infantry in a heartbeat.
Now, being a former Marine I now about obsolescence, for my first two years I was stationed at MCLB Barstow where, when an old jeep, truck or tank arrived at the rail dock, job #1 was to send a bunch of privates with rattle cans of olive drab to paint out the white star.
Disgusted I returned to the boneyard and pulled some wiring and found these two relays;





Well,I finally pulled the radiator out (good thing I did, one of the mounting flanges was loose) and after removing the stock fan shroud with the small 18" Flex a lite fan I set the Merc Mystique assembly inbetween the tanks and all I had to trim was the top mounting tab.



For controllers, I ended up using a Ford PDB out of a mid 90's truck, for the relays
and this one had all the relay positions I'd ever need.


...and isolated the rail mounted on the side,



took my trusty Dremel and ground clearance for the larger footprint 70 amp relay



...these aren't available at my local Ford dealer as they seem to obsolete parts like these every 2 - 5 years. Luckily all of the relays were free from my local wrecking year and I bround my mutimeter to check each on for continuity and serviceability.



and used this nasty smelling Devco epoxy that dries harder than the plastic itself. I accidentely broke a corner out of the main PDB and maing a form with blue plumbers tape packed this Devco in and after letting set overnight took 20 minutes with a titanium bit in the Dremel to grind off the flashing. I had a lot of soldering to do but in the end it all went well.



...the controllers





...and the PDB I mounted on the right fender skirt





I essentially used the diagram below for my wiring.



...here's another one I used to figure out how to wire the override switch, turned out it was easier than I thought.


Got it wired so far as the dash and when wiring the three way override switch I failed to touch the case to ground so got a failure, it wasn't until I got to work and thought about it and felt those donkey ears spring up. In the meantime I soldered in the diode between the Override and the Control circuit.


...this is a Rat Shack switch.




Got the switch wired in and as it turns out didn't need to be grounded to function, it was the inclusion of that diode.
I got the switch mounted and am underway cleaning up my underhood electrics with that negative bus bar and the Ford PDB, It's going well and lucky I got into it found my primary wire to the starter solenoid coming loose from the connector. Broke out my trusty hobby vise that I hadn't used in four decades and crushed the connector onto the wire.

After a long drive (100 miles +/-) involving highways speeds, upgrades, bumpy dirt and gravel roads at speed. 'Black Betty' never got above 190* and, if I switched to Override she cooled down to 160*!

Using this system for the past 9 months and I've had no failures despite extended driving over last winters washboard cut into the ice on my commute by trucks running LaGrande tire chains. (Can't say the same for my radio and ignition switch, they both rattled loose breaking continuity)