5.3l overheating problem
Hi. I did have the same problem in my 72 Blazer. After a while i did find the problem. i solved my problem like this. The coolant line from the trothlebody, direckt in to radiator. not to the coolant tank. The radiator cap blocked my outflow to the coolant tank. Modyfying radiator cap. dont need it, have one on the coolant tank, this worked for me.
Thread Starter
Teching In
Joined: Feb 2008
Posts: 33
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From: Pottstown, PA
Just a couple of things.
Are you using the cylinder head vent lines?
Why do you turn the fans on at 170 degrees?
Is the electric fan pulling or pushing? Pulling is best. If they are running going down the road the may impede air flow at high speed.
I have two LS swaps. First is a 4.8 in a 98 wrangler. 2000 4.8 with mechanical fan and 4.0 radiator. Stock thermostat. Runs at 195 degrees no matter the temp out side.
Second is a 99 Wrangler with a 2000 LS1. Novak radiator with Spal fan. Temp sensor in the lower left corner of the radiator. Painless sensor that is on at 205 degrees and off at 195 degrees.
It runs very cool no matter what the driving speeds.
Is there a a small chance of a bad head gasket or cracked head? Worth doing a pressure test? Either can put allot of heat in the cooling system.
When you get to 260 degrees does it vent out of the radiator?
Jim
Are you using the cylinder head vent lines?
Why do you turn the fans on at 170 degrees?
Is the electric fan pulling or pushing? Pulling is best. If they are running going down the road the may impede air flow at high speed.
I have two LS swaps. First is a 4.8 in a 98 wrangler. 2000 4.8 with mechanical fan and 4.0 radiator. Stock thermostat. Runs at 195 degrees no matter the temp out side.
Second is a 99 Wrangler with a 2000 LS1. Novak radiator with Spal fan. Temp sensor in the lower left corner of the radiator. Painless sensor that is on at 205 degrees and off at 195 degrees.
It runs very cool no matter what the driving speeds.
Is there a a small chance of a bad head gasket or cracked head? Worth doing a pressure test? Either can put allot of heat in the cooling system.
When you get to 260 degrees does it vent out of the radiator?
Jim
Electric fan is pulling it is a fully shrouded fan that is sold as a kit with the radiator, it seals fully around the core and works really good. I had a 2nd small pusher fan in front of the radiator, but several people told me that is a no no, because the small fan was more of a restriction for the big fan and could cause a problem, so I took it out.
It only gets to 260 if you hold 75 for 20 min or so, and by the time you would pull over and look it is down to 220 or so, It might be pushing some coolant to the catch can but never out on the ground and not more than the bottle handles. When I check the radiator, it is always full all the way up into the filler neck.
I don't think it has a cracked head or bad gasket, it dosen't show any signs of dirty coolant and no air bubbles in the coolant.
Thanks
Dave
Thread Starter
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Joined: Feb 2008
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From: Pottstown, PA
Check your heater core or shutoff valve. THE LS ENGINE NEEDS COOLANT FLOW ALL THE TIME THRU THE HEATER CORE. Sorry for the yelling. Make sure you have constant flow. If the heat is off then you need to install a heater valve out of a Ranger or GTO. One that still allows coolant to flow thru the heater hoses. If you doubt your setup then just run a U-shaped heater hose at the water pump temporarily and see if it still overheats.
The first thing you notice about LS engines are that they don't hold much coolant compared to the old small block.
You can still run 15/1 A/F ratio at light cruise and it should not overheat.
The newer 5.3s are great. They run good all the time and are over 300 hp.
The first thing you notice about LS engines are that they don't hold much coolant compared to the old small block.
You can still run 15/1 A/F ratio at light cruise and it should not overheat.
The newer 5.3s are great. They run good all the time and are over 300 hp.
Thanks
Thread Starter
Teching In
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From: Pottstown, PA
Thanks
Thread Starter
Teching In
Joined: Feb 2008
Posts: 33
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From: Pottstown, PA
thanks
Dave
Are you competely sure your fan is pulling air into the engine bay?
I had this exact problem and it was a reverse rotating fan.
My 5.3L with full bolt-ons stays at 176* (180* thermostat) with a 1" thick, 16x20" aluminum core radiator and NO fan running at 70 mph. I have almost no frontal area, and have no shrouding in place (Mazda RX7). Unhook your cooling fan and see if your temperature changes. I bled the system by pulling the upper radiator hose out, and filling it until no more air came out (with the hose held above the motor). Worked great.
I had this exact problem and it was a reverse rotating fan.
My 5.3L with full bolt-ons stays at 176* (180* thermostat) with a 1" thick, 16x20" aluminum core radiator and NO fan running at 70 mph. I have almost no frontal area, and have no shrouding in place (Mazda RX7). Unhook your cooling fan and see if your temperature changes. I bled the system by pulling the upper radiator hose out, and filling it until no more air came out (with the hose held above the motor). Worked great.
You shouldn't need the fan at highway speed. If you do you have another problem. Seal around the radiator inlet so the airflow goes through the radiator and not around it.
Make sure the intake hose is not collapsing at speed from pump suction. It should have a spring in there. This is something you will only see at engine revs. Run the engine at highway RPM and feel the intake hose to see if it is restricting flow.
I assume you are using the stock belt routing and the tensioner is good? No pump slipping at speed?
Make sure the intake hose is not collapsing at speed from pump suction. It should have a spring in there. This is something you will only see at engine revs. Run the engine at highway RPM and feel the intake hose to see if it is restricting flow.
I assume you are using the stock belt routing and the tensioner is good? No pump slipping at speed?
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Brett Foote Thread Starter
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Joined: Feb 2008
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From: Pottstown, PA
You shouldn't need the fan at highway speed. If you do you have another problem. Seal around the radiator inlet so the airflow goes through the radiator and not around it.
Make sure the intake hose is not collapsing at speed from pump suction. It should have a spring in there. This is something you will only see at engine revs. Run the engine at highway RPM and feel the intake hose to see if it is restricting flow.
I assume you are using the stock belt routing and the tensioner is good? No pump slipping at speed?
Make sure the intake hose is not collapsing at speed from pump suction. It should have a spring in there. This is something you will only see at engine revs. Run the engine at highway RPM and feel the intake hose to see if it is restricting flow.
I assume you are using the stock belt routing and the tensioner is good? No pump slipping at speed?
Intake hose does have a spring in it and we checked at rpm for any hose collapse problems. Stock belt and tensioner, all in like new condition, no slipping.
thanks
Dave
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From: Pottstown, PA
Yes we installed a autometer gauge to check agenst the factory gauge, both read within 5 deg of each other. We have also checked with contact thermometers and non contact (IR) thermometers. All read within a couple degrease of each other.
On The Tree
Joined: Jan 2007
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From: Florida
Your right,there is no ECT shut off. I looked back threw HP tuners and the only thing is Engine over temp EQ ratio vs RPM. That sucks, I would rather it shut down then melt the block, all the PCM does is throw more fuel at it to richin it up. There is a lean cruise setting that I have disabled i.e. Lean Cruise Leanout Rate
Dave,
Post up a couple of pictures of your engine bay. Maybe someone can see "something" to help you out.
How do you have your radiator hoses routed into the radiator?
Have you tried driving it without a thermostat?
Post up a couple of pictures of your engine bay. Maybe someone can see "something" to help you out.
How do you have your radiator hoses routed into the radiator?
Have you tried driving it without a thermostat?
Thread Starter
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From: Pottstown, PA
http://www.flickr.com/photos/29380571@N03/
It almost appears that the fan shroud covers too much of the radiator, compared to the fan opening and the actual footprint of the radiator
It looks like the fan shroud covers 50% of the radiator.
At speed, It would seem that this would constrict airflow through the radiator, but at slower speeds, (less load) the fan would pull enough air.
Do you have access to a large fan without such a closed shroud?
Many factory style shrouds have vents in them to allow air to pass through them at highway speeds.
Just my humble opinion.
It looks like the fan shroud covers 50% of the radiator.
At speed, It would seem that this would constrict airflow through the radiator, but at slower speeds, (less load) the fan would pull enough air.
Do you have access to a large fan without such a closed shroud?
Many factory style shrouds have vents in them to allow air to pass through them at highway speeds.
Just my humble opinion.
Thread Starter
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From: Pottstown, PA
We tried a Taurus fan I had laying around thinking the fan didn't flow enough air at high speeds, saw a small change but not enough to say it fixed the problem. I thought the same thing with restriction causing the air to not want to go through the radiator.
I actually thought that the aerodynamics or lack there of with the Jeep might not let enough air flow through the radiator at high speeds, and that the winch and bar on the front might be deflecting air around the grille. We took the winch and bar off and ran it and again saw minor change but not the expected huge difference. still
thanks for your thoughts, at this point I am open to any ideas out there.
I have ben thinking about going to a manual fan to see if that makes a difference.
-Dave
I actually thought that the aerodynamics or lack there of with the Jeep might not let enough air flow through the radiator at high speeds, and that the winch and bar on the front might be deflecting air around the grille. We took the winch and bar off and ran it and again saw minor change but not the expected huge difference. still
thanks for your thoughts, at this point I am open to any ideas out there.
I have ben thinking about going to a manual fan to see if that makes a difference.
-Dave
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Joined: Dec 2001
Posts: 922
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From: Lexington Park, MD
I still have the mechanical fan that I removed from my 5.3L. I removed it because there wasn't enough room and would have hit the radiator, but I probably could have made it work with some more fabrication and moving stuff around. Looks like this if you're interested in trying it:
It's a big fan. Oh, also, with the elec fan I have installed, I installed a three position switch on the dash. I can leave it in the default position which is ECM controlled, forced on position, and forced off for water/mud crossing. Important if you wheel in those conditions because the high speed elec fans will grenade/break blades and get all out of balanced.
It's a big fan. Oh, also, with the elec fan I have installed, I installed a three position switch on the dash. I can leave it in the default position which is ECM controlled, forced on position, and forced off for water/mud crossing. Important if you wheel in those conditions because the high speed elec fans will grenade/break blades and get all out of balanced.
Thread Starter
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From: Pottstown, PA
Wow that fan is huge! I don't know if I could make that fit and not hit everything! I was actually looking at older steel blade style non electric clutch style fans I think they used them 2000-2004 or so with just the standard clutch. Just need to find one to try without spending too much on a fix i don't know will work. Not sure what I would do about a shroud for testing, If i know it would fix the problem I would fab up a nice aluminum shroud.
-Dave
-Dave
TECH Resident
Joined: Dec 2001
Posts: 922
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From: Lexington Park, MD
Yeah, it is big 
It's all out of a 2005 Envoy. The OEM shroud is a split upper and lower piece. It's a clutch style, but elec controlled for on/off. I always wondered what the CFM rating of that beast was. Since it rides off the water pump, it may not spin as fast as the elec types, I'm not really sure. I just looked at your pics again. Looks like yours is pretty cramped like mine is.
It's all out of a 2005 Envoy. The OEM shroud is a split upper and lower piece. It's a clutch style, but elec controlled for on/off. I always wondered what the CFM rating of that beast was. Since it rides off the water pump, it may not spin as fast as the elec types, I'm not really sure. I just looked at your pics again. Looks like yours is pretty cramped like mine is. It's not your cooling fan at highway speeds. You either have air in the system or something isn't circulating correctly. If you have shrouding forcing air though, the fan is NOT the problem, electric fans on almost any car don't run above 30-40 mph. If you need a fan running at high power at 40+ mph, you're masking another problem at best.
I'd try a new water pump before I dove too deep into other things.
I'd try a new water pump before I dove too deep into other things.
It's not your cooling fan at highway speeds. You either have air in the system or something isn't circulating correctly. If you have shrouding forcing air though, the fan is NOT the problem, electric fans on almost any car don't run above 30-40 mph. If you need a fan running at high power at 40+ mph, you're masking another problem at best.
I'd try a new water pump before I dove too deep into other things.
I'd try a new water pump before I dove too deep into other things.