Cooling fan issue
Thread Starter
Instructor
Joined: Aug 2017
Posts: 246
Likes: 6
Cooling fan issue
Today the car idled 30 minutes in 80 degree temp. Upon turning the car off, coolant overflowed from the resevoir.
What are common reasons why the fan would fail to come on?
1996 LT1 auto coup.
Thanks
What are common reasons why the fan would fail to come on?
1996 LT1 auto coup.
Thanks
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
I think your fans are coming on, but your cooling system needs all the same typical maintenance the many folks' do. Clean debris from in front of the radiator, and flush the system out.
Le Mans Master
Joined: Oct 2004
Posts: 6,314
Likes: 508
From: South-central Missouri
Too "coincidental"?
IF the system was recently flushed and refilled and properly "burped", the level in the overflow reservoir shouldn't have been filled above the "COLD" line before the engine was allowed to come to operating temperature. Otherwise there won't be sufficient reserve space in the overflow reservoir for expansion, once the engine heats up!
OR...Air leaking into the system* will result in coolant not being drawn back into the system as the motor cools. (This is a major clue of air leaking into the system!
) Next time the motor is started, the temp may zoom up quicker and higher than normal, and coolant overflows from the overflow reservoir, especially after the motor is shut off (trust me!). *Radiator pressure cap or using a screw-type hose clamp in place of the factory spring clamps very often a source for trouble! (Dang screw clamps are easy to install, BUT they also require periodic checking to see they haven't lost their grip. Spring clamps are a bitch to deal with w/o the proper tool to remove/replace them, but damn well worth it in terms of trouble-free installation!!
)
)Last edited by Paul Workman; Apr 28, 2018 at 09:40 AM.
Melting Slicks
Joined: Oct 2016
Posts: 2,024
Likes: 363
From: Central Alabama
OK since yours is a 96 the fans work a little different than my 92. Looking at the wiring diagram: when the system hits 219 both fans should come on at low speed. This is done by placing the fans in series using the contacts of a de-energized third relay. When High fan is commanded relays 2 and 3 energize placing the fans in parallel.
My suggestion would be verify radiator is clear of debris.
Refill cooling system.
Start car and monitor coolant temp on the LCD display. When it reaches 219 both fans should come on. If they do then you have another issue.
Could be as simple as a bad radiator cap or as bad as a bad water pump or clogged radiator.
Did you just buy this car? Has it previously worked properly? The reason I ask is if relay 3 is replaced with a 4 pin relay the low fan circuit could be disabled. At least that's the way I read the circuit.
Also a defective relay 3 could cause no low fan function.
My suggestion would be verify radiator is clear of debris.
Refill cooling system.
Start car and monitor coolant temp on the LCD display. When it reaches 219 both fans should come on. If they do then you have another issue.
Could be as simple as a bad radiator cap or as bad as a bad water pump or clogged radiator.
Did you just buy this car? Has it previously worked properly? The reason I ask is if relay 3 is replaced with a 4 pin relay the low fan circuit could be disabled. At least that's the way I read the circuit.
Also a defective relay 3 could cause no low fan function.
Racer
Joined: Sep 2012
Posts: 491
Likes: 40
From: Mardi Gras City
St. Jude Donor '19
reprogram ecm
the 1996 OBD2 cars can be reprogramed thru the ECM to turn the fans on at lower temp. even though my car has a manual fan override switch I did the reprograming and consider it money well spent.
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Le Mans Master
Joined: Oct 2004
Posts: 7,706
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From: Everett WA
C4 of Year Finalist (appearance mods) 2019
As noted in post #3 & #7 you need to check to insure that the radiator is clear of debris. The system may have been flushed but if the radiator fins are clogged with debris (which VERY often they are) the system will not function properly. This also holds true if there is a bunch of debris between the AC condenser and the radiator.
On the 95 (and I believe your 96 functions the same way):
First fan comes on around 227 degrees
2nd fan does NOT come on until around 237 degrees.
BUT when car is standing still and you turn on the AC.... BOTH fans come on at their high speed. (this is pretty easy to check).
On the 95 (and I believe your 96 functions the same way):
First fan comes on around 227 degrees
2nd fan does NOT come on until around 237 degrees.
BUT when car is standing still and you turn on the AC.... BOTH fans come on at their high speed. (this is pretty easy to check).
Zen Vet Master Level VII
Joined: Mar 2016
Posts: 5,218
Likes: 1,174
From: Southlake, TX
Here is what I found with my "perfectly normal" system that over heated. I cleaned out the junk and the system worked perfectly.
Drifting
Joined: Feb 2008
Posts: 1,537
Likes: 177
From: NE Ohio
2024 C4 of the Year Finalist - Unmodified
Have you checked the "in between" space for the radiator and the AC condenser? You can have a super squared away system and if the junk in between blocks your air flow, nothing will keep your car cool.
Here is what I found with my "perfectly normal" system that over heated. I cleaned out the junk and the system worked perfectly.
Here is what I found with my "perfectly normal" system that over heated. I cleaned out the junk and the system worked perfectly.
Yep me too
Thread Starter
Instructor
Joined: Aug 2017
Posts: 246
Likes: 6
Did you have to take it apart to get it clean?
As i said in my battery thread. I am slowely going thru this car upgrading and modernizing as i go. I am looking at going to a 3 row polished aluminum radiator, new water pump, hoses, and high performance fans.
You might say, "thats alot of $ for nothing". I am planning the powerplant overhaul. My choices are, rebuild the current LT4 to 383, 500 rwhp. This is likely to go upwards of 10k, Or..... just suck it up and drop some coin on a new GM LT4 plug and play crate engine.
A super charged 650 hp engine will probably require rear axle mods. Sounds like a fun toy huh.
With my kids all grown up, and no wife, i can finally have a cool old hotrod Corvette!!
As i said in my battery thread. I am slowely going thru this car upgrading and modernizing as i go. I am looking at going to a 3 row polished aluminum radiator, new water pump, hoses, and high performance fans.
You might say, "thats alot of $ for nothing". I am planning the powerplant overhaul. My choices are, rebuild the current LT4 to 383, 500 rwhp. This is likely to go upwards of 10k, Or..... just suck it up and drop some coin on a new GM LT4 plug and play crate engine.
A super charged 650 hp engine will probably require rear axle mods. Sounds like a fun toy huh.
With my kids all grown up, and no wife, i can finally have a cool old hotrod Corvette!!
Drifting
Joined: Feb 2008
Posts: 1,537
Likes: 177
From: NE Ohio
2024 C4 of the Year Finalist - Unmodified