Cadillac Owners Forum banner

1 - 20 of 49 Posts

·
1996 Fleetwood hearse
Joined
·
58 Posts
Discussion Starter #1
I found on here some posts that others were experiencing overheating issues and wanted to ask this: Has anyone replaced the stock thermostat with a 160 degree one in their LT1 and then reprogrammed the fans to kick on at a different temperature? I was reading this post: http://h-body.org/people/projects/building_lt1/lt1 info.html and the writer, Scott, talks about reprogramming the ECM just for the fans with the 160 thermostat. I want to do this but finding a cheap programmer is difficult. Anyone use another source like a computer with OBD software to accomplish this?
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,072 Posts
Use the stock 180 degree thermostat, find the real cause of any "overheating", don't screw with the fan sequencing.

Many emissions systems change loop operation at about 160 degrees coolant temp. Run the engine too cold and you open a real can of worms. A "happy" engine runs at between 190 and 210.
 

·
1996 Fleetwood hearse
Joined
·
58 Posts
Discussion Starter #3
Use the stock 180 degree thermostat, find the real cause of any "overheating", don't screw with the fan sequencing.

Many emissions systems change loop operation at about 160 degrees coolant temp. Run the engine too cold and you open a real can of worms. A "happy" engine runs at between 190 and 210.
I use this car for parades and last weekend I watched the temp climb above 230 with both fans running. The car was idling mostly with my foot on the brake and you could feel it start to slightly buck. My plans are to change thermostat, water pump, and flush the system. I don't know exactly what the previous owner did or didn't do to this car but normally it runs about 195 at idle in park with the air on. I was thinking also about a larger radiator, maybe an aluminum one, but yeah I need to figure out why it did what it did.
 

·
Registered
70 Deville 78 Seville 92 Deville 03 Deville
Joined
·
718 Posts
The stock radiator would have cooled it when it was new. A Cadillac should be able to sit in bumper to bumper traffic effortlessly. It has to be a gummed up radiator or a circulation issue. A lot of Cadillac owners mistakenly put sealant in their radiators due to some old urban legends.
 

·
Registered
Joined
·
224 Posts
The problem with using a 160 degree thermstat is not the fan settings.
What happens is the ECM thinks the engine is not warm.
So it will likely run in open loop with a richer mixture.
Open loop wastes fuel, raises emmisions & restricts performance.

The reason cooler temps are used for performance is a coolar intake allows for a more dense air.
Also running the heads & block cooler reduces the chance of detination & allows for more ignition advance.

There is an ideal engine temp range the engine was designed for.
Too cold and the engine clearances are greater because parts have not expanded from the heat.
It creates more engine wear.
The oil would be contaminated faster with carbon, raw fuel, & unburned moisture.
Spark plugs would probibly benifit from a hotter temp range to avoid fouling.

If your looking for a performance calibration, want to run premium / race fuel, not concerned with fuel economy, don't have local emission testing, & not worried about additional wear... Then run a coolat T-stat.
 

·
Registered
Joined
·
224 Posts
You are best served to find the cause of the overheating.
Never remember a water pump that wasn't leaking cause a overheat problem.
Either it turns & pumps or it don't.
In general all cars maybe 1 in 1000 chance the impeller broke off or rotted out.
Or a problem with the incorect part, poor working aftermarket, wrong gasket, or ports clogged with gasket sealer.

Before doing any work look for leaks including under the water pump.
You said both fans are working. I'm gussing you have the duel electric fans.
Make sure you have good air flow from the fans. Nothing clogging the front radiator or condensor.
Sometimes the condensor coils fins get all mashed down, deteriorated, & inbeded with junk.
I run a hose thru the front & back side of condensor & radiator to improve the airflow.
Be suprised how much junk is comes out.

Make sure your not low on coolant or have air pockets. There is a bleader on the T-stat.
I got a few parts & piped the bleader into a hose draining away from the engine.

Check is the overflow bubbling. Just a bad radiator cap will cause the coolant to boil too soon & overheat.

How do you know the sensors are reading correctly? For a few dollars the engine coolant temp sensor & warning light sender can be changed.

The radiator is plenty large enough for normal use. Could be clogged up. They don't seem to be that expensive online but can't speak for the quality.

Run some coolant flush thru it before draining. Get a garden hose and keep spraying water in every hose / port till it comes out the other side clean. To flush the best is to remove both knock sensors in the block. Too bad they don't always come out like they should. Remove the heater hoses & flush the core. There is a heater core restrictor to change that costs a few bucks that gets restricted. The restrictor won't cause the overheating but just maintence. Have seen in the junkyards a lot of these where all the hoses had buildup of calciam or rust restricting the flow. Again chaging the hoses is good maintence.

Hard to say if you have a 180 or 195 T-stat from here. I would put in a 180F T-stat.
 

·
Super Moderator
2014 ELR
Joined
·
9,699 Posts
230 is not overheating. The secondary fan is programmed above that. If you want it to cool off, simply put AC on MAX, even with the heat cranked up. This will engage the secondary fan and bring temps down fast.

If you want the fans to come on sooner, get the PCM re-programmed, but keep the 180 stat.
 

·
Registered
'93 SedanDeville 60 Special
Joined
·
232 Posts
I use this car for parades and last weekend I watched the temp climb above 230 with both fans running. The car was idling mostly with my foot on the brake and you could feel it start to slightly buck. My plans are to change thermostat, water pump, and flush the system. I don't know exactly what the previous owner did or didn't do to this car but normally it runs about 195 at idle in park with the air on. I was thinking also about a larger radiator, maybe an aluminum one, but yeah I need to figure out why it did what it did.
I'll give a different slant so you have more thought about your question or path you want to take

IMHO, Heat does not give best performance, nameplates run engines hot for smog purposes
It is not just coolant heat, but the total of everything else if engine or tranny heat, CATs, exhaust manifolds, etc
all additive to heat soaking everything including total engine bay and everything in it

One answer as to OBD-II,
Yes if it is a good scanner it would allow to send a temp fan ON command,
in this case via scanner can command fans to come on when you want
But this is only temp, if scanner or engine is turned off then that temp command is gone and would have to command it on again when wanted with scanner.

Almost all my customers I do custom tuning for request commanding fans on either at cooler temps or with a higher fan rotation, depending on the age of vehicle and how GM setup coolant fans are commanded on or off.

Most cases stock Tstat is around 194 degrees. yet as I show below the 2 GM fan command table methods

In newer GM vehicles the fans being controlled is about how much the fans should rotate by the settings in the PCM fan table.
Notice in this 2016 Caddy the PCM is only commanding the fan to barely rotate (4%) and that is above 192 coolant degrees.
As you see in the table as example even if temp is around 113 C (235 F) command is for only 72 % rotation

If not changing to like a 170 deg Tstat at least via tune the fan setting table could call for higher rotation (no sooner then 192 deg) starting at 89 C and slant higher rotation higher as coolant temp goes higher.
This at least means then cooling all temps down sooner which also means lower temps to like fuel in fuel rails to cooler intake air temps.

IF swapping in a cooler Tstat then via tuning commanding even higher fan rotation

575558


In older (like pre 2006) the PCM is only using a temp coolant fan trigger as to when off or commanded on

In this case is with a 2004 Caddy CTS-V

Low speed fan is not commanded on until 219 F deg
In this case it could be changed in tune to at least come on at the stock Tstat opening around 192 deg
and If putting in a cooler Tstat then command ON at the temp that one begins to open

These are simple changes if wanting to lower temps over what some of us do such as my
car which I also race.

1. Installed a higher flowing radiator
2. installed 170 deg Tstat
3. installed a heat ex-changer to pull heat out of engine oil
4. moved engine oil filter, using one double size over stock one
5. added oil filter lines so total oil is 3 quarts more then stock volume
6. multi hood vents to pull heat out of engine bay
7. cooling intake air temps via water/meth injection
8. Installed manual tranny cooler
9. Installed rear end cooler.
10. running colder step of sparkplugs

With those cooling down changes the HP/Tq went up and not down from stock hotter temps and cooler
overall temp makes a better cylinder charge, less engine knock, less timing and torque pulled

575557
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,072 Posts
FWIW running a cold heat range spark plug has exactly NOTHING to do with engine operating temperatures. "Hotter" spark plugs allow the electrodes and center insulator to heat up and thus remove carbon and soot from the plug tip. "Colder" plugs pass off much of the tip and shell heat to the head/coolant and are used in higher rpm racing applications. Run cold plugs in a street engine and you stand a very good chance of plug fouling.

If you can't fill 'em with facts, baffle 'em with bullshit.
 

·
Registered
Joined
·
224 Posts
At times I thought about installing an additional fan controller on the fleetwood to lower operating temp.
Not that it overheats. Juat the 2nd fan kicks in at a higher temp than I like.
Could reprogram the ECM. But I don't have or intend to buy.

That why I looked at an aftermarket fan relay & switch kit.
Put the sensor in the drivers cylinder head coolant port.
Connect to the secondary or maybe add a 3rd cooling fan.
The ones I used had an adjustment to dial in the on temp.

I would like one of those factory mechanical fan set-ups.
Haven't seen one in the yard & not looking to spend much.

Back to the orignal post, is there something wrong or are we trying to improve.
 

·
Registered
'93 SedanDeville 60 Special
Joined
·
232 Posts
FWIW running a cold heat range spark plug has exactly NOTHING to do with engine operating temperatures. "Hotter" spark plugs allow the electrodes and center insulator to heat up and thus remove carbon and soot from the plug tip. "Colder" plugs pass off much of the tip and shell heat to the head/coolant and are used in higher rpm racing applications. Run cold plugs in a street engine and you stand a very good chance of plug fouling.

If you can't fill 'em with facts, baffle 'em with bullshit.
I guess you missed in my post "what some of us do such as my car which I also race."

Nothing in my content was about total stock engine but with the total of my cooling changes allowed
for best performance included 1 step colder and also shorter gap plugs

Along with being stroked and using 11.3:1 compression, with boost and headers and injecting a colder charge to cylinders with water/meth

A stock sparkplug will not work well at all and reason sparkplug makers sell colder step over what the stock plug design is and yes the cylinder temps are lower and that also means coolant temps are cooler
 

·
Registered
70 Deville 78 Seville 92 Deville 03 Deville
Joined
·
718 Posts
Another BSing thread that doesn't help the OP. His car doesn't need to be re-engineered to make it run like it is supposed to. I'd bet on the radiator unless the fans aren't working. Not sure what year car it is: I don't know much about LT1 water pumps so that could be a culprit in some way.
 

·
Registered
Joined
·
224 Posts
Another BSing thread that doesn't help the OP. His car doesn't need to be re-engineered to make it run like it is supposed to. I'd bet on the radiator unless the fans aren't working. Not sure what year car it is: I don't know much about LT1 water pumps so that could be a culprit in some way.
It was the OP that suggested modifying the T-stat temp and programming because of an alleged overheating problem.
The thread shows what a can of worms that opens up for a stock parade car.

1st question is was it overheating or just running stock max temps.
Seems that the 2nd fan turns on around 230F.
Didn't state the temp warning light was on.
OP monitoring the temp thru the temp programmer or plug in scan tool?
Car was designed for the normal user to pay no attention to the temp until the light came on or car leaked.
Factory manulal defines overheating as the coolant boiling. Which is at least 250F.

2nd is just do basic inspection & maintence.

OP stated both fans are running.

Again water pumps that aren't leaking & belts tight don't cause occasional overheating.
The LT1 pump was sold as even more reliable because it's driven off the cam sprocket.
No belts to slip. If the ball bearings were falling out it would also leak.
If the drive coupling broke the car would overheat very fast.

3rd could it be that there is drivability problem the OP is associating with running on the warm side but is something else. Such as an ignition system breaking down. EGR sticking. A tired fuel pump. Fuel filter clogging. Or restricted Cat converters which also makes the car run a bit hotter.
 

·
1996 Fleetwood hearse
Joined
·
58 Posts
Discussion Starter #15
It was the OP that suggested modifying the T-stat temp and programming because of an alleged overheating problem.
The thread shows what a can of worms that opens up for a stock parade car.

1st question is was it overheating or just running stock max temps.
Seems that the 2nd fan turns on around 230F.
Didn't state the temp warning light was on.
OP monitoring the temp thru the temp programmer or plug in scan tool?
Car was designed for the normal user to pay no attention to the temp until the light came on or car leaked.
Factory manulal defines overheating as the coolant boiling. Which is at least 250F.

2nd is just do basic inspection & maintence.

OP stated both fans are running.

Again water pumps that aren't leaking & belts tight don't cause occasional overheating.
The LT1 pump was sold as even more reliable because it's driven off the cam sprocket.
No belts to slip. If the ball bearings were falling out it would also leak.
If the drive coupling broke the car would overheat very fast.

3rd could it be that there is drivability problem the OP is associating with running on the warm side but is something else. Such as an ignition system breaking down. EGR sticking. A tired fuel pump. Fuel filter clogging. Or restricted Cat converters which also makes the car run a bit hotter.
The previous owner installed a temp gauge on the driver's side of the block on an unused port. It is pretty accurate. What concerned me is that while running the air conditioner and forcing the fan on, normally the vehicle runs around 190 to 210. With both fans running it shot up to above 230 and the engine started to slightly buck and we were running in 65 - 70 degree weather. That, to me is a clear sign that I've got a problem even though the idiot light didn't come on. What I read on the post I referenced was based on changing the thermostat out to a 160 and using a Hypertech Power Programmer to adjust the fans to operate at a different temperature. I'd rather not have to go that route but much rather not have to tear into the engine to fix a blown head gasket or worse. When I parked the car at the end of the parade, the temp went back down to 195. So, I'm looking to change the thermostat and possibly the water pump with a full flush of all the coolant. I'd like to go with a little cooler thermostat without causing other issues but now I'm wondering if I could change out the coolant temp sensor with one that will 'lie' to the PCM and force the fan on sooner. I may just change it out anyway to be on the safe side. The fans work as they should, I'm not comfortable with the temps going that high and the engine acting up like it did. BTW drove home just fine, no high temps and it'll get up and run 80 on the interstate like nobody's business. Not too shabby for a hearse. Oh and no codes on ignition issues, fuel pump is new, EGR is new and the CATS are functioning within specs. The second fan is supposed to come on around 212 degrees which it does.
 

·
Super Moderator
2014 ELR
Joined
·
9,699 Posts
As we've pointed out, your car is not overheating.

Bucking points to an IGNITION problem.
Possibilities:
  • ICM on driver's head (uses the head for cooling, so entirely possible that heat is causing problems here, and they're known to fail)
  • plugs, wires, coil, coil wire... how old, when were they done?
  • opti (people blame them for everything, but are often not the problem)
  • SLIGHTLY leaking water pump will drip out of the weep hole on the bottom of pump and will drip on opti and belt. You often don't notice this because the drip is slow, and the coolant gets slung around by the belt so there is no drip on the floor. With car OFF and engine COLD, reach down and feel the bottom of the pump. Should be bone dry.
 

·
Registered
Joined
·
224 Posts
"I'm wondering if I could change out the coolant temp sensor with one that will 'lie' to the PCM and force the fan on sooner."

In the 80's maybe early 90's performance companies sold a low cost plug in device that was said to improve performance. In reality it was only a resister with a male & female plug. It pluged between the temp sencer and factory temp sencer. To trick the ECM in thinking the engine is a different temp to get more fuel. I believe they lowered the temp reading to make the engine run richer. Around that time the cooling fans were mechanical on V8's or done with a seperate switch. Early ECM controlled much less. It was a poor mans chip. I question if it did much good besides make a company money.

Don't mess with providing the computer false sencer readings. It could create all kinds of other problems. Like the EGR kicking in when the car is too cold. Or ignition timming retarded more. Could go on with most ECM systems. Everything is calibrated around the temp.

To change when the fans run you have 3 options.
1. Reprogram
2. Tie in an aftermarket sencer & relay like I discussed
3. Install a mechanical switch inside tied to a relay & wired to only work with the key on

I've done #3 on a car in Vegas. Not that it overheated. Just the stock high speed came on later then I liked.
Also helps the A/C work better.

Stock radiators are already alumimun... And plastic.

Chevy had a lot of problems with V8 head gaskets in certain years.
The LT1s & iron heads are very solid & don't have those issues.

That said the secondary fan doesn't seem to kick on much even in Vegas.
I only know after running for a while in the drive or checking after driving.
If the A/C is off & car is idling at 60F - 70F it seems to take a while for a 180F T-state to open and a long time for the primary fan to kick on. That's with the V03 extra capacity cooling (one of the fans is larger).

"The second fan is supposed to come on around 212 degrees which it does."
212F is way too low for a secondary stock fan setting.
It might kick on the 2nd fan at 212F because of the A/C pressure, not the temp.
Couldn't find any number in the factory manual.

Take it or leave it I found this chart for B & D bodies.
Don't know what differences there could be between years & option codes.
It shows the stock 2nd fan on temp at 232F (not factoring A/C pressure kicking it on).

Fan Mode Temperature A/C Pressure
-----------------------------------------------------------------
Primary (RH) Fan ON: 107 C / 225 F 189 psi
Primary (RH) Fan OFF: 103 C / 217 F 150 psi
-----------------------------------------------------------------
Secondary (LH) Fan ON: 111 C / 232 F 240 psi
Secondary (LH) Fan OFF: 107 C / 225 F 210 psi

Also it's been reported the PCM will turn off the fans at higher vehicle speeds, above 48 MPH since running fans can actually impede airflow through the radiator at high speed. Each fan also has a minimum running time. Once activated, the primary fan will run for a minimum of 50 seconds, and the secondary fan for a minimum of 26 seconds. Finally, certain Diagnostic Trouble Codes (DTCs) may cause the PCM to turn on one or both fans.

Just start with the basic inspection & maintence of the cooling system.
 

·
Registered
Joined
·
224 Posts
One Hypertech Power Programmer has been said to turn the primary fan on at 176 degrees (instead of 225), and the secondary fan on at 191 (instead of 232).
You could imagine the problem if you had a 180 T-stat. The fans would almost always run.
 

·
1996 Fleetwood hearse
Joined
·
58 Posts
Discussion Starter #19
As we've pointed out, your car is not overheating.

Bucking points to an IGNITION problem.
Possibilities:
  • ICM on driver's head (uses the head for cooling, so entirely possible that heat is causing problems here, and they're known to fail)
  • plugs, wires, coil, coil wire... how old, when were they done?
  • opti (people blame them for everything, but are often not the problem)
  • SLIGHTLY leaking water pump will drip out of the weep hole on the bottom of pump and will drip on opti and belt. You often don't notice this because the drip is slow, and the coolant gets slung around by the belt so there is no drip on the floor. With car OFF and engine COLD, reach down and feel the bottom of the pump. Should be bone dry.
Water pump is not leaking. Plugs and wires with cap and rotor were done before I got the car in June. Car runs fine otherwise, just the slow going at the parade got me concerned. The car does run a little rich even after the bad EGR was replaced. I replaced all 4 oxygen sensors (had a bad one) and the EGR solenoid as well. Only leak I have is from the transmission pan which was loose when I got it and after tightening it, still leaks a little when parked but if you drive the car a bunch it stops so the gasket is bad.
 

·
1996 Fleetwood hearse
Joined
·
58 Posts
Discussion Starter #20
One Hypertech Power Programmer has been said to turn the primary fan on at 176 degrees (instead of 225), and the secondary fan on at 191 (instead of 232).
You could imagine the problem if you had a 180 T-stat. The fans would almost always run.
Yeah that is why Scott mentioned reprogramming the PCM if going to a 160 thermostat. I'm going to start small and focus on the coolant and thermostat. There is some stuff called water wetter that is supposed to help cooling and have been hearing about it from my vintage Mustang group on FB. If it will help the 65/66 Mustang 6 cylinder cooling issues, it may just work for the Caddy.
 
1 - 20 of 49 Posts
Top