HoLLo

iTrader: (17)

Ok so i replaced the busted hose I had causing a coolant leak with a barb and 2 clamps.. and I examined the entire system, the leak is now fixed (i will definitely see after I drive around).. But my fans are not even coming on at all. and the temp got into the red after I let it idle for awhile, so it had a chance to turn the fans on. Where do I begin to check, trial/error?

Also, when I first go for a drive (this has been happening since before I replaced this hose) The temp will climb up into the red zone about 260, and then all of a sudden after a few minutes of driving the temp will drop down to around 180-190 and stay there, which I'm guessing is when the thermostat is opening. Is that a bad water pump causing that or what?

haacer

iTrader: (1)

Make sure that your PCM is seeing the temp. Check to see what it's reading with a scantool.

http://shbox.com/1/4th_gen_tech2.html#cooling

Cooling System Operation and Testing


Electric cooling fans attached to the radiator keep the LT1 from overheating when there is little or no air passing through the radiator core (car going very slow or stopped and engine running). It is normal for the temps on the gauge to go up to the middle or past middle of the gauge before the fans kick on. The middle of the gauge is in the range of 210º - 220º. With factory programming, the PCM will command low speed fans (or primary fan) "ON" at 226º and "OFF" at 221º and high speed fans (or secondary fan) "ON" at 235º and "OFF" at 230º. The fans should come on before it gets to any part of the red zone. (see "dual fan configuration" below about primary and secondary fans)
The f-body LT1 uses a 180° thermostat as stock.

The PCM gets it's temp readings from a sensor that is in the water pump. If the reading the PCM receives is inaccurate, the fans may not come on at the correct time. The PCM also uses this temperature for lookup in fuel calculation tables. If there is a problem that causes the reading to be always low (cold), the PCM will add extra fuel. This can cause hard starting when warm and an overly rich condition when running.

The gauge gets it's information from a sensor that is in the driver's side head. Inaccurate gauge readings can be from this sensor or it's wiring (the wire burned on a header pipe is common). The temp that the PCM sees can be monitored with a scan tool and compared to the gauge reading. They should be close, but don't expect them to be "perfectly" synchronized.

The fans are programmed to come on when the a/c is turned on. A/c Pressure monitoring sensors feed the PCM info and depending on the situation, the PCM may command the fans off for brief periods. Also, when the car reaches sustained higher speeds, the fans may be commanded off so incoming air can flow through the radiator unimpeded and provide the cooling needed.

Fans will also come on when the SES lamp comes on. The PCM does this when certain (most) DTCs are detected to protect the engine from a situation where it may overheat.


There are two versions of the dual fan configuration:

# 1993-1994 - Primary and Secondary fans that operate at only one speed. When initially commanded on, only the primary fan (driver side) comes on. It operates alone at full speed. If the temp threshold is met for addtional cooling, the secondary fan (passenger side) also is commanded on. At this point, both fans are running at full speed.
These fans use a two relay architecture that can be seen in the fuse/relay panel that is under the hood.

# In late 1994 and into 1995, there was a change to low and high speed fans. When initially commanded on, both fans will come on at a low speed. When the high speed temp threshold is met, they both bump up to high speed. A three relay architecture is used for this fan version (seen in the fuse/relay panel). By adding a third relay, low speed can be achieved by running the power to the fans in series. This way, each fan does not get full voltage and runs at a slower speed. High speed happens when the relays switch to provide full voltage to both fans. Low speed is less noisy and should result in greater fan longevity. High speed is not always needed.


2 Relay System PCM Commanded Fan Operation PCM Wire Color Grounded Fan Operation Relay Operated
#1 #2 #3
Primary@226º Drk Grn @A11 Primary (LH) fan full speed X - n/a
Secondary@235º Drk Blu @A10 Secondary (RH) fan full speed X X n/a
3 Relay System Low Speed@226º Drk Grn @A11 Low Speed (both fans) X - -
High Speed@235º Drk Blu @A10 High Speed (both fans) X X X
For both fans to operate in either system, both relay leads must be grounded. Grounding only the Drk Blu wire will result in only the RH fan operating at high speed.



Here are some fairly simple things to check for various complaints:

~Fans are not operational at any time~


# Check fan fuses in the underhood fuse/relay panel
# Check fan relays (same location). Aside from getting out any electrical equipment to test the relay, you can swap it with another one (such as the fog lamp relay) and test for function. See if the relay works for the fog lamps and/or the swapped-in relay makes your fans work. Nearly all the relays in the panel are the same, except for maybe the ABS relay.
# You can jumper two pins on the DLC that should cause the fans to come on. 1993-1994 cars with the 12 pin DLC can jumper pins A and B. On a 1993, that is the same way that you would retrieve trouble codes from the ecm. The 1994 won't give you any codes, but the fans will engage. 1995-1997 uses pins 5 and 6 on the 16 pin DLC to initiate what is called "field service enable mode". That will cause the fans to come on and operate most sensors for sanity checking. After placing the jumper on the correct pins, turn the key to ON (don't start). If the fans work after jumpering the DLC, your PCM is capable of operating the fans and all fan wiring/relays should be ok.
# Deeper problems can be solved through testing and using the wiring schematic.


~Fans don't come on except when the a/c or SES is on~

~Temp gauge continues to rise with no automatic fan operation~


# With a scan tool, check to see what temp the PCM is seeing from the sensor in the water pump. Make sure you are aware of the temps the fans come on (stated in the beginning of this article). If the temp it sees is incorrectly low, it won't know to turn the fans on. Another possibility is that the temp is really ok, but the gauge is reading wrong. That is why you need to use the scan tool to see and compare the readings. Info on testing wiring and sensor can be found here.
# If that looks ok, then your PCM may have issues. You could always try resetting the PCM by pulling the PCM BAT fuse for about 30 seconds.

HoLLo

iTrader: (17)

Yeah, so the fans dont come on even with the A/C on. I traded fuses around for all the coolant fan fuses, and no luck. Any more ideas?

haacer

iTrader: (1)

The temp going all the way up to 260 sounds like a sticky thermostat or maybe a bad sender. I'm assuming that you've already tried everything on the shbox page: swapping fuses, swapping relays, turning on ac, checking sender is plugged to water pump, etc...

You need to know how the temp that the PCM is seeing is related to actual temp and also how actual temp is related to gauge temp. If you read the whole article at shbox, you know that there are two sensors involved. One runs the gauge and one send the signal to the pcm.

I bought a small infared non-contact thermometer from Harbor Freight.

http://www.harborfreight.com/cpi/cta...emnumber=93983

Something like that should give you at least a better idea of what the actual temperature is.

The way that you described your temp as changing quickly from boiling over to normal makes me wonder what kind of condition your cooling system is in. It's important to make sure that you have a good coolant mix (50/50 or your pref) and a bled cooling system before you start worrying about fans.

As I mentioned previously, when I had a cooling system leak it acted like that. Of course, my temp didn't come down, but that's another story.

I didn't notice where you were located, but if you're within driving distance of Long Beach, Ca I'd be happy to help you out with a scan and my premium infared thermometer.


Also, if you're desperate not to involve anyone with a scan tool, temps with corresponding resistances are found at shbox. You could conceivably make a rig to hook up a multimeter to the PCM sender and check the resistance against data from a infared thermometer as the car warmed up.

http://shbox.com/1/4th_gen_tech2.html#ect

HoLLo

iTrader: (17)

I replaced my theromstat no more than 3k miles ago, with a Duralast. Also the sender wire to my guage was cut, so I spliced the wire and coupled them together. It worked fine. But it never immediately started doing the 260 jump thing until the past month. I checked all fuses, they look good. Swapped relays, no luck. Turned on AC, no luck. Plug IS plugged into water pump. My water pump gets HOT as hell, very scaulding. Is that normal? I use 50/50. I have not bled my coolant yet, but over the past few months it has leaked so much I'm sure it has done the equivalent.

I'm pretty sure I just fixed my coolant leak. https://ls1tech.com/forums/attachmen...3&d=1193709467

That hose was busted up. So I cut it and put a hose barb and clamps on it. So far it seems to be working better. I have only heard my fans turn on ONCE since I've had this car.

haacer

iTrader: (1)

You should check the splice on the gauge sender to be sure that it isn't grounding out.

To diagnose this problem, you'll need either a scan tool, or the patience to wire a multimeter to the ECT and note resistance while noting temperature with a thermometer as previously described.

Bleeding the system can make a big difference too...

HoLLo

iTrader: (17)

The splice was done with a wire crimp coupler and wrapped in tape. I don't think it's grounding. But I will double check.

Is there a certain scan tool I should look to get?

and thanks for all your responses and help so far!

haacer

iTrader: (1)

I'm glad to help. I'm only sorry I haven't been more helpful just yet...

Your car is OBD II, being 96+. You can buy pretty much any code scanner, but that will only give you codes. I have a cable from Tunercat and scanning software. The whole package probably ran less than $200 and allows me to flash the PCM, pull codes, and check sensor values.

http://www.tunercat.com/tnr_desc/links.html#scan

Another option is to check out Ebay. Just be careful not to get something that only pulls codes. You want something that will give realtime sensor data. Alternately, find a shop that will loan you one or a pal. Aamco used to do free scans. I think Autozone discontinued their free scan deal.

I happen to know a number of mechanics in the area, so when I get stuck I can go hit up my bud for his Snap-On scanner that scans anything. That thing cost something like $5k... Try to find a friend before anything.

On the other hand, there is a whole forum of other F-body experts here... Surely someone must have some input on howto do this without a scan tool...... Anyone?

HoLLo

iTrader: (17)

Anyone have any ideas until I get a scantool?