Coolant temp high with a/c running?

[88sogreatv8]

My temp on the 1uz usually runs around 87 to 95 degrees even on the hottest days with my 3 core alum radiator and duel fan setup. But when turning a/c on it climbs to sometimes 104. Is this normal. The compressor is always on i will add when the a/c button is pushed . Im not sure if the compressor is supposed to toggle on and off though. Ive seen that on most a/c systems.

 

[ivan129]

Hi,

In answer to your question… Yes, the aircon compressor should toggle on & off once the cabin has cooled / reached the desired temp; assuming you have cabin temp sensors correctly fitted and wired. The ECU will adjust engine parameters like idle speed and ign timing to compensate for the compressor load.

I’ve read a few of your posts in the past and only working from memory here.
Your engine has been swapped into another car and you’re running an aftermarket radiator and twin thermos, right.
So here are a bunch of things to ponder over:-

Have the heads ever been off the engine? If so, is it possible the head gaskets are fitted incorrectly? (on the wrong sides)

Are you running a radiator with sufficient cooling capacity for the engine / car?

Are your cooling fans running in the correct direction? Pushing air into the engine bay. Take the fans off and check!

Do you have full battery voltage at the fans. Just a 1V drop will reduce the efficiency of your fans and there will be a loss of cooling efficiency.

Are you getting enough air into the radiator and through the engine bay? Raising the back of the bonnet can sometimes work.

Have you tested your thermostat to make sure its fully opening.

Could be a good idea to drop it to an 82 degree C one.

Do you have the coolant hoses fitted in the correct place on the radiator so the coolant flows the right way through your radiator.

Are you using a good quality coolant?

Have you flushed the engine and radiator lately? Open the drain plugs when you do this.

Engine tune ok? Is the engine running lean. This can cause overheating.

Is the ignition timing correct?

If you have an aircon radiator in front of the engine radiator, (most are) is it blocked or restricted?

Do you have a secondary aircon cooling fan fitted to the aircon radiator and it is working in the correct direction, has battery voltage.

If all of the above check out ok and you’re still having over heating problems, you could consider fitting a remote oil cooler to the engine with a cooling fan. That should knock a couple of degrees out of it.


Also found this on AliExpress. You might like.

 

[ivan129]

Picture is of a really neat radiator cap with an analogue temp gauge fitted to the top on AliExpress for about 5bucks


Good luck.

 

[88sogreatv8]

Picture is of a really neat radiator cap with an analogue temp gauge fitted to the top on AliExpress for about 5bucks


Good luck.

Ivan 129 by the way you have been very helpful many times now on this forever project.

The engine came from a local salvage yard, I own a transmission shop so I have a good relationship with this yard . The engine came out of an 90’ LS400 with 80k original miles. The heads as far as I know have never been removed.

I am currently running a OPL Radiator , it does have a slight seep in one of the tube I just found Saturday, and am currently trying to find my receipt , but finding another vendor for my mx73 cressida that makes bolt in radiators that are 3 core is hard to come by.

The Mishimoto cooling fans are pulling towards the engine , the engine preforms great with no a/c running. On the hottest of days 100 degrees Fahrenheit the engine will run at the hottest at 206 degrees once again Fahrenheit. I just upgraded the cooling fan from in front of the condenser, which helped significantly.

The Cooling fans are direct wired to a switch on the dash. The A/c fan is wired all factory so when the compressor is turned on the fan comes on about 60 seconds later

I did find out recently that the thermostat was not opening until 95 to 105 degrees. I replaced it with a SC400 Thermostat that opens around 87 degrees I believe . Coolant system is nice and clean and I only run the Toyota red from the dealer , obviously mixed with distilled water.

The engine runs great ,timing is on point

The only thing that I can think of is the compressor never turns off, additionally I cant get the temp controls to work from cold to hot. I have never been able to figure out the heat in this car. I think its all electric with some vacuum switches , but pretty sure that the vacuum only controls the mode doors.

I do wonder if the compressor never cycling off to cool down is my issue . I also wonder if not being able to adjust the temperature in the cabin is my problem. My biggest problem is finding information for the mx73 chassis’s hvac. Most people bash these cars drifting, and don’t worry about a/c or heat.

 

[ivan129]

Ivan 129 by the way you have been very helpful many times now on this forever project.

The engine came from a local salvage yard, I own a transmission shop so I have a good relationship with this yard . The engine came out of an 90’ LS400 with 80k original miles. The heads as far as I know have never been removed.

I am currently running a OPL Radiator , it does have a slight seep in one of the tube I just found Saturday, and am currently trying to find my receipt , but finding another vendor for my mx73 cressida that makes bolt in radiators that are 3 core is hard to come by.

The Mishimoto cooling fans are pulling towards the engine , the engine preforms great with no a/c running. On the hottest of days 100 degrees Fahrenheit the engine will run at the hottest at 206 degrees once again Fahrenheit. I just upgraded the cooling fan from in front of the condenser, which helped significantly.

The Cooling fans are direct wired to a switch on the dash. The A/c fan is wired all factory so when the compressor is turned on the fan comes on about 60 seconds later

I did find out recently that the thermostat was not opening until 95 to 105 degrees. I replaced it with a SC400 Thermostat that opens around 87 degrees I believe . Coolant system is nice and clean and I only run the Toyota red from the dealer , obviously mixed with distilled water.

The engine runs great ,timing is on point

The only thing that I can think of is the compressor never turns off, additionally I cant get the temp controls to work from cold to hot. I have never been able to figure out the heat in this car. I think its all electric with some vacuum switches , but pretty sure that the vacuum only controls the mode doors.

I do wonder if the compressor never cycling off to cool down is my issue . I also wonder if not being able to adjust the temperature in the cabin is my problem. My biggest problem is finding information for the mx73 chassis’s hvac. Most people bash these cars drifting, and don’t worry about a/c or heat.

Ok, well best you fix the coolant leak first.
I really don't like manual control over the cooling fans. Too easy to overheat your engine if you're too slow to hit the switch.
If it were me, I'd consider purchasing a basic thermal switch so you can turn on the fans automatically & safely.
My twin 14" fans are powered from a relay mounted right beside the fans with a heavy 6mm cable connected directly to the alternator output. The relay is PWM switched from my ECU (soft start) and programmed to switch on at 88C with a 3degree hysterysis from memory.
On a hot day when my fans come on they usually stay on, but on cooler days they toggle on when stopped and off when moving.
Peak current when they turn on is around 30A each so hence the soft start. When running they pull about 10 - 12A.
You might like to do that with your aircon compressor. Purchase a simple thermal switch, (plenty on eBay for less that 20bucks) mount the thermocouple in the cabin, tap into the compressor wiring and insert the thermal switch contact. Wire it so the compressor turns off once at / below your comfort zone.

 

[88sogreatv8]

Ok, well best you fix the coolant leak first.
I really don't like manual control over the cooling fans. Too easy to overheat your engine if you're too slow to hit the switch.
If it were me, I'd consider purchasing a basic thermal switch so you can turn on the fans automatically & safely.
My twin 14" fans are powered from a relay mounted right beside the fans with a heavy 6mm cable connected directly to the alternator output. The relay is PWM switched from my ECU (soft start) and programmed to switch on at 88C with a 3degree hysterysis from memory.
On a hot day when my fans come on they usually stay on, but on cooler days they toggle on when stopped and off when moving.
Peak current when they turn on is around 30A each so hence the soft start. When running they pull about 10 - 12A.
You might like to do that with your aircon compressor. Purchase a simple thermal switch, (plenty on eBay for less that 20bucks) mount the thermocouple in the cabin, tap into the compressor wiring and insert the thermal switch contact. Wire it so the compressor turns off once at / below your comfort zone.

The a/c fan does come on automatically, it is the engine cooling fans i have on a switch. I also have a digital monitor that reads the coolant temp, voltage, and o2 data. I originally tried the thermistor, but kept having issues, so i bought a switch and it has worked well.

I will say i found out yesterday the main control unit for the a/c and heat needs replaced. Alldata has this test where if the unit has a open circuit the a/c will be stuck on cold. and sure enough when it is selected all the way to cold, with the multimeter on pins 3 and 4 it is in open loop, where it should have 2500 ohms of resistance. I am going to replace this unit first then i will check back after and see if this is why the compressor wont toggle on and off.

From what i understand about a/c once the cabin reaches its desired temp , the compressor toggles off giving the compressor a break to cool down . Normally from what ive read around 10 mins roughly , then turns back on. ??

 

[88sogreatv8]

The a/c fan does come on automatically, it is the engine cooling fans i have on a switch. I also have a digital monitor that reads the coolant temp, voltage, and o2 data. I originally tried the thermistor, but kept having issues, so i bought a switch and it has worked well.

I will say i found out yesterday the main control unit for the a/c and heat needs replaced. Alldata has this test where if the unit has a open circuit the a/c will be stuck on cold. and sure enough when it is selected all the way to cold, with the multimeter on pins 3 and 4 it is in open loop, where it should have 2500 ohms of resistance. I am going to replace this unit first then i will check back after and see if this is why the compressor wont toggle on and off.

From what i understand about a/c once the cabin reaches its desired temp , the compressor toggles off giving the compressor a break to cool down . Normally from what ive read around 10 mins roughly , then turns back on. ??

Also do you know anyone that sells a 3 core radiator for a mx73 Cressida. I bought mine from OPL and they are out of business. The Mx83 radiator has different mounting tabs

 

[ivan129]

if you do a google or eBay search you will find hundreds of suppliers of 3 core MX83 radiators for under 200$.
I use a modified version of an MX radiator in my car.

 

[88sogreatv8]

if you do a google or eBay search you will find hundreds of suppliers of 3 core MX83 radiators for under 200$.
I use a modified version of an MX radiator in my car.

will a mx83 radiator work in a mx73?