1uz over heat issues

[88sogreatv8]

So 95 ls400 is overheating at idle.
I have a 3 core radiator , and i did have just a 15" electric fan bolted directly to the radiator. It did ok ,but on hot days is would get up to 240f at idle.
So i got a mishimoto dual fan setup with a shroud thinking it would help direct the heat better. Well today, i found it it made it worse.
Before it seemed to have to be a hotter day and sitting at multiple lights before it got up there. Now it overheats badly when even driving down the road . Got up to 250 with the fans running . I had to pull over and shut off the car to prevent head gasket failure.

 

[Zuffen]

Normally if a car overheats when driving it's lack of airflow but seeing it's an LS400 it shouldn't have a problem.

Are the fans in front or behind the radiator?

Also are you 100% sure the air is being either blown or sucked back toward the engine and not the other way. Easy enough to get wrong.

If all is well in the above I'd be replacing the thermostat as a first step.

Try and report back.

 

[88sogreatv8]

the fans are behind the radiator , i did 100% verify the fans are pushing thru the radiator. i have a replacement thermostat. i wanted to try the trd 70 degree or the mits 76 degree option ,but haven't ordered either. I do have a ls400 thermostat, but skeptical it will change anything especially because its a duralast and i think the Cressida doesn't have enough room to dissipate heat. im going to also order some hood risers to see if there is a change, but they look so stupid .
id really like to install hood louvers but , I am far from a body guy

 

[Zuffen]

First question is you say the fans are behind the radiator , i did 100% verify the fans are pushing thru the radiator. If the fans are behind the radiator they need to pull the air. it may be a typing error but worth making sure it's right.

As an aside fans are more efficient pulling air rather than blowing air.

Check the thermostat works by putting in some boiling water and see if it open. If it does put in and see what effect that has.

Rather than buy hood risers why not take the hood off and go for a run and see what happens?

Plenty of Cressidas have had the UZ treatment and they all work so you have an issue you need to work through by making one change at a time and then let us know what's happening and we'll do our best to help.

 

[88sogreatv8]

thank you for the technical information . to make the fan location clear. the fans are in-between the radiator and the engine not the radiator support.

they are pushing air thru the radiator and a/c condenser and out the front grill. i am going to pull the thermostat this morning and check to see if it is opening at 80 degrees. i have a replacement one if needed

thank you for the help. ive owned many different vehicles with different setups and by far this community has been the most helpful of the bunch

 

[88sogreatv8]

First question is you say the fans are behind the radiator , i did 100% verify the fans are pushing thru the radiator. If the fans are behind the radiator they need to pull the air. it may be a typing error but worth making sure it's right.

As an aside fans are more efficient pulling air rather than blowing air.

Check the thermostat works by putting in some boiling water and see if it open. If it does put in and see what effect that has.

Rather than buy hood risers why not take the hood off and go for a run and see what happens?

Plenty of Cressidas have had the UZ treatment and they all work so you have an issue you need to work through by making one change at a time and then let us know what's happening and we'll do our best to help.

So i havnt changed the thermostat, but what i did do was remove the radiator shroud that i made from a piece of aluminum.

I had it there for directing more air flow to the radiator,but i think i may have been causing heat issues. Not sure will re Evaluate as the temperature outside goes up.

The hottest it got this time was 235 and was climbing. It only did it when i was just cruzing at 30-40 mph. If i came to a stop the fans would cool it down and if i got it above 45 mph it would also start to drop

 

[Zuffen]

Certainly sounds like a lack of airflow at 30-40.

It may be worth making sure all escape routes for air in front of the radiator (hole in the radiator support etc.) are blocked.

Some googling on air flow into radiators may surprise you what works to get air that comes through the grille to flow through the radiator.

 

[88sogreatv8]

Certainly sounds like a lack of airflow at 30-40.

It may be worth making sure all escape routes for air in front of the radiator (hole in the radiator support etc.) are blocked.

Some googling on air flow into radiators may surprise you what works to get air that comes through the grille to flow through the radiator.

i was check to make sure there aren't open holes anywhere. what do u think about replacing the oe thermostat with the trd performance.

 

[88sogreatv8]

today i found a 77 degree thermostat for a sc400 so i decided might as well try. so replaced the the stat and will drive tomorrow.

i did a little science experiment with the old one and it says 82 degrees Celsius and didnt open till 92 degeees!!!
will update tomorrow

 

[SC500]

they are pushing air thru the radiator and a/c condenser and out the front grill

if your fans are in between the radiator and engine, then isn't it blowing the wrong way? Shouldn't it be pulling air through the ac condenser and radiator and though to the engine.

My dad had the same problem with his kit car last summer. His engine would be very hot when cruising around town at whatever speed, but it would cool down a little bit when he was stopped at a light. It ended up being that the electric fans were wired up backwards and were pushing air out the front of the car, and not pulling it in.

 

[88sogreatv8]

if your fans are in between the radiator and engine, then isn't it blowing the wrong way? Shouldn't it be pulling air through the ac condenser and radiator and though to the engine.

My dad had the same problem with his kit car last summer. His engine would be very hot when cruising around town at whatever speed, but it would cool down a little bit when he was stopped at a light. It ended up being that the electric fans were wired up backwards and were pushing air out the front of the car, and not pulling it in.

So what your saying is the hot air is blowing from the radiator is blowing onto the engine ? rather than out the front of the vehicle

 

[ivan129]

Air must enter the heat exchanger "radiator" from the outside front of the car where the air is cooler. The air then leaves the radiator at the rear into the engine bay (assuming your radiator is mounted in front of your engine). When fitting electric fans you can sometimes get fooled which way they a blowing air so its always a good idea to remove them and check. If mounted in front of your radiator they should blow air into the radiator. If mounted behind the radiator (engine bay side) they should such air and heat from the radiator. Another thing that many people overlook is voltage drop. Cooling fans can pull 10+ amps each when operating (sometime 20 - 30A in rush on startup) so as little as .5 Volt voltage drop at the fans can means quite a loss in fan speed. Its always a good idea to power your electric fans from a suitable relay mounted close the the fans to minimise voltage drop. Run a heavy fused power feed from the battery to the relays. You might notice that modern cars have what's called a soft start, on their electric fans. This is done by PWM the power to the fans reducing high in rush current. They often have a soft shut off too.

 

[88sogreatv8]

Air must enter the heat exchanger "radiator" from the outside front of the car where the air is cooler. The air then leaves the radiator at the rear into the engine bay (assuming your radiator is mounted in front of your engine). When fitting electric fans you can sometimes get fooled which way they a blowing air so its always a good idea to remove them and check. If mounted in front of your radiator they should blow air into the radiator. If mounted behind the radiator (engine bay side) they should such air and heat from the radiator. Another thing that many people overlook is voltage drop. Cooling fans can pull 10+ amps each when operating (sometime 20 - 30A in rush on startup) so as little as .5 Volt voltage drop at the fans can means quite a loss in fan speed. Its always a good idea to power your electric fans from a suitable relay mounted close the the fans to minimise voltage drop. Run a heavy fused power feed from the battery to the relays. You might notice that modern cars have what's called a soft start, on their electric fans. This is done by PWM the power to the fans reducing high in rush current. They often have a soft shut off too.

thank you for the information . I really appreciate it . i have since reversed the fans from pushing to pulling . i also found a 77 degree thermostat for a sc400 . i need a good hot day to confirm its fixed but, the help of the lexstreme forum and all its memebers has been a lifesaver!!!!!!!!!!!

 

[ivan129]

Dam; I wish I could edit my last post again. Must have been pissed when I posted it. The gramma and spelling was terrible.
This should read a little better.

Air must enter the heat exchanger "radiator" from the outside front of the car where the air is cooler. The air then leaves the radiator at the rear into the engine bay (assuming your radiator is mounted out front and in front of your engine). When fitting electric fans you can sometimes get fooled which way they are blowing air; so it’s always a good idea to remove them and check the air flow direction. If mounted in front of your radiator they should blow air into the radiator. If mounted behind the radiator (engine bay side) they should suck air and heat out and away from the radiator. Another thing that many people overlook is voltage drop. Cooling fans can draw 10+ amps each when operating (sometime 20 - 30A as in rush current on startup) so a small voltage drop as little as .5 volt at the fans can means quite a loss in fan speed. It’s always a good idea to power your electric fans from a suitable relay mounted close the fans to minimize voltage drop at the fans. Run a heavy fused power feed from the battery to the fan relay/s. You might notice that modern cars have what's called a soft start, on their electric fans. This is done by PWM the power to the fans reducing high in rush current. They often have a soft shut off too.

 

[dweinhart]

If you are still having issues, you should look into a possible BHG. Not as uncommon as you might think.Back in the USA, I lived in AZ and regularly pounded my 1uz, flooring it everywhere with AC on full up hills at when it was 115 degrees outside and never had overheating issues. Fast forward to today...bought another one and had overheating issues. 1st problem was that I was losing water via rusted freeze plugs (previous owner didn't use antifreeze)and 2nd problem was BHG caused from warpage from the overheating. Shop did head gasket without cutting block and it still overheated. Ended up having to pull motor again to replace HG again (with good fasteners) and shave both heads and block.

 

[herrybrook21a]

i found it it made it worse.
Before it seemed to have to be a hotter day and sitting at multiple lights before it got up there. Now it overheats badly when even driving down the road . Got up to 250 with the fans running . I had to pull over and shut off the car to prevent head gasket failure.