Supra Forums banner

1 - 5 of 5 Posts

·
Registered
Joined
·
15 Posts
Discussion Starter · #1 ·
Morning.

Bit of an odd one here. I've a 7M-GTE that's running an aftermarket EMS and of course I do keep an eye on the temperature gauge, as you do.
Head gasket is new, on ARP studs, decked block and remanufactured head casting.
The thermostat opens at 82C (as stamped on the body), confirmed by boiling it in water, the system pressurises as expected and I'm running a Koyo 56mm radiator.
Fans are electric as the factory mechanical setup decided to go south, they're twin fans from a Mondeo V6, sealed as well as I could against the radiator.
There is no trays as none of that came with the car and I haven't gotten around to making new one.
All hoses are clean, the block has been flushed repeatedly, all lines are confirmed to be unclogged.

I'm noticing the engine likes to operate around 88-90C on the gauge, and I have set the fans to turn on at 91C with a 4 degree hysteresis (considering this is 9C above the thermostat opening temperature), which makes it run quite often while cruising around at motorway speeds. On steep uphills at low speeds it stays around the 91C mark as well, with the fans at full tilt.

I've never seen it go above just under half the dashboard gauge, but those aren't known for being exactly accurate.

Now, what's the temperature these engines are supposed to be running at? I can't find any spec anywhere, but the head castings being as soft as they are, I'm inclined to think anything above 95C is the no-go zone. But on the other hand there is a 115C temperature switch for the secondary condenser fan on the factory installation so... maybe I'm being too safe?

Thanks.
 

·
Registered
Joined
·
6,639 Posts
Aluminum is fine at 95c.. the cast aluminum that toyota used might be on the lower range for anealing at 150c which you are far from.
 
  • Like
Reactions: MZ024

·
90T
Joined
·
665 Posts
stock thermostat is 90C. It is fine to go up to 230F occasionally in stop and go with ac on. Coolant will boil around 256F 50:50 glycol at 0.9 bar.
 

·
Registered
Joined
·
15 Posts
Discussion Starter · #4 ·
So I'm being too safe is what we're getting at. If the factory tstat is 90 degrees C the engine surely must be designed to operate closer to the 100 mark than 90, considering tstat opening range, hysteresis and so on and so forth.

I'm using Aisin ULL fluid, 5L of it and then some 4L of straight water, so the boiling point should be around the 115degC mark or so I expect (it's supposed to be 129C if you use it as it comes out the bottle). Given the fans and the much larger radiator, it should never get that hot (it gets to 32-35degC in the absolute peak of summer) at any rate.

That's quite reassuring, many thanks to both of you. I'll get to making some ducting which will surely help, just for completeness.
 

·
Registered
Joined
·
15 Posts
Discussion Starter · #5 ·
Just as a follow-up on this, the ducting has helped immensely, and I am fairly sure I can still do a better job at sealing it, plus cleaning the exchanger stack (oil coolers most notably). The coolant will now stabilise around 78degC (one could say that's even too cold) on a 15degC ambient while cruising at 80km/h, and the fans won't stay permanently on while doing slow speed uphills, instead, they will cycle at around 60-90 second intervals.
 
1 - 5 of 5 Posts
Top