Severe duty fan clutch / 180 degree T/Stat possible issue

kennyrodgers · March 12, 2017, 06:00 PM

Hi Folks,
I fitted a Hayden severe duty fan clutch and 180 degree thermostat a few months back. 1994 454 TBI. I'm not sure if this is an issue or not but thought to ask the question anyway.
Freeway driving is fine, the fan will kick in on an incline or when the factory temp gauge gets to 200f. However, when driving on normal roads, light traffic conditions, stopping at a red light for instance then accelerating up to 40 mph and cruising at 40 mph the temp gauge is going from approx 180 to 200 then the fan will kick in. This happens at least every five minutes. The temp drops quickly to about 180 and the cycle repeats. I've no coolant leaks and visually everything looks good. It's only started doing this since I changed the fan clutch and T/Stat.
Nothing to worry about or does it warrant further investigation.....the water pump is new also.
Thanks in advance guys.
Pete.

stanDman111 · March 12, 2017, 06:22 PM

what was it doing with the old clutch fan?
could be the new clutch?
just a guess

Rickf1985 · March 12, 2017, 07:30 PM

I have the same problem, the fan clutch seems to be a bit on the conservative side. I probably have the same clutch but it has been too long since I got it and I do not remember. I have thought about going back to a standard heavy duty clutch.

tmsnyder · March 13, 2017, 09:40 AM

IMO the system you created is doing exactly what you designed it to do. You have a great cooling system, once it kicks in it dumps so much heat that it's shutting down the thermostat to keep from over-cooling the engine.

If you don't want to see it cycle high/low so drastically then put in a more standard 195F thermostat. The extra 15deg temperature differential compared to outside air temperature will help even more with cooling the engine before the fan has to come on.

Rickf1985 · March 13, 2017, 10:55 AM

I didn't see the 180 thermostat reference. It should not be cycling much with that thermostat in there since the clutch should be kicking in at around 200-215 degrees. If you go with the 195 thermostat them it will be engaged even more. A 195 thermostat on a vehicle with a marginal cooling system already is just asking for trouble. You will be able to cook eggs on the dogbox!

tiinytina · March 13, 2017, 01:42 PM

Gone has a heavy duty fan clutch in her now after the original blew out on ramp from PA turnpike at breezewood.. then goes into jet engine mode always on vs overheat.

Yes the new heavy duty clutch with the OEM replacement T-stat works as it should intermittently on hills and such but also yes every start up from a stop if the engine is warm it runs for a couple of seconds, and may repeat as the transmission shifts up. once at speed it is fine... and by at speed... 55 or so.. yes below 40 or so not enough air over the engine to keep it in its happy place... above that the air flow from MPH speed helps. '

Tina

tmsnyder · March 13, 2017, 01:58 PM

If he had a marginal cooling system, he'd be reporting a problem with overheating. He's not.

Here's what the OP wrote in August: Well,Just done a 400 mile round trip and everything was hunky dory. I used the ALDL Droid set up on the way home. temps were from 188 on the Motorway up to 195 whilst pulling some fairly steep grades. The new fan kicks in at 195 and she's back down to 188 in under two minutes.Happy days and thanks all again.

What he's describing now is 2 parts of a cooling system operating independently. One, the fan clutch, is pushing the radiator temperature down from 205 if it ever gets up there. It's successful while hill-climbing and shuts down once the radiator cools off. The other part is the thermostat, it's trying to keep the engine temperature at least 180F at a minimum. The two parts are getting into a ping pong type action where the temperature is bouncing back and forth between the two set points.

It's mostly because the fan clutch takes time to disengage, its operation is based on heat transfer into the clutch to activate, and out of the clutch to disengage. It takes time to cool down and disengage, even after the engine is done climbing a hill and is no longer making excess heat. During this time the fan is continuing to move lots of air over the radiator, overshooting its set point and continuing to cool the radiator below 180. The thermostat closes in response to the cool water coming from the radiator b/c it's fairly fast acting, and holds the engine temperature from dropping below 180F. The water in the radiator continues to cool b/c of the air flow from the fan and road speed and the thermostat cracks open and maintains 180 by sipping cool water from the radiator until the next hill climb.

If you change your thermostat back to the standard 195F, the oscillations will be greatly reduced. You'll have the engine running at 195F and the fan clutch heated up and just waiting to jump into action at 205. That heating-up time lag will be reduced, and once it kicks in and pushes the temperature down it won't go too far before the thermostat closes a little and holds the temp at 195.

kennyrodgers · March 13, 2017, 06:49 PM

Cheers all,
The ping pong analogy makes sense to me and can see how that could be happening.
Going back to what I wrote in August.... That trip was mostly motorway ( freeway as you guys call it ) driving at 50 to 55mph so good airflow into the radiator. This recent one however, we never got above 40mph due to the roads we travelled on.
I think I'll go back to a 195 T'Stat and see how we go from there. Maybe I should have just done the changes one at a time.
I'll get one ordered and report back.
Thanks again all.

rs72z · August 16, 2017, 12:37 PM

Your engine is designed to run with a 195 stat. If you go to a 185 the ecm will add more fuel to try and get the temp to 195, it thinks the engine is still warming up. The result will be more fuel burned. That's what we saw when the tbi engines first came out.