Bypassing heater core (loop or block off)?

[Devin LeBlanc]

Well I've got a question. When bypassing the heater core should I block each port off, or hook the two lines together?

I have had them blocked off for the last year and a half but in the summer time (today it was 120+ out) with the A/C on my temps start creeping up only with freeway driving.

Have done a leak down and compression check no leak down to the cooling system what so ever. Compression is all 170 at the lowest 176 at the highest (9.2:1 compression ratio) There are no exhaust gasses in the cooling system. The car does not have a BHG. Cooling system has been pressurized to 20 PSI with no leaks.

Doesn't loose any coolant or over heat with normal driving. Has a 3 row dual pass nascar radiator with a properly shrouded Tarus fan on high. Brand new water pump, new radiator hoses, tried a 190F and 180F temp thermostat with the same issue.

 

[IBoughtASupra]

Loop them together. I have never blocked coolant lines off except the rear nipple for the twins on the JZ motor. Always loop as it will avoid hot spots.

The coolant will just sit there in the spot you capped off.

 

[Devin LeBlanc]

Is that a spot that flows? Even when its hooked up the valve shuts it off so coolant doesn't flow to the heater core right?

 

[suprarx7nut]

Is that a spot that flows? Even when its hooked up the valve shuts it off so coolant doesn't flow to the heater core right?

Thats my understanding. With the valve closed the coolant sits regardless.... That shouldn't be cause for a rise in temps. Is the radiator brand new? Can you ditch the taurus fans and restore the higher flow stock fan?

 

[Devin LeBlanc]

The Tarus fan is not the issue it does the same with a shrouded clutch fan. Radiator is brand new. I think the system can't cope with the 125F air temps. Im 4 speed with the 4.30 rear end so the rpm's are high at freeway speeds.

 

[T701jz]

The Tarus fan is not the issue it does the same with a shrouded clutch fan. Radiator is brand new. I think the system can't cope with the 125F air temps. Im 4 speed with the 4.30 rear end so the rpm's are high at freeway speeds.

This. Turn off your ac and see the difference

 

[IJ.]

Does it have an undertray?

 

[Poodles]

Even when the valve is closed, coolant flows to the heater core.

 

[Devin LeBlanc]

IJ, That is about the only thing I don't have. I heard Toyota still has them for like 70.00.. Might end up picking one of those up!

 

[suprarx7nut]

IJ, That is about the only thing I don't have. I heard Toyota still has them for like 70.00.. Might end up picking one of those up!

When I worked at Toyota it was around $110 with employee discount. That was two years ago. Nevertheless, completely worth it.

 

[Devin LeBlanc]

We have a dealer account through toyota.

 

[CyFi6]

Looking at the diagram in the tsrm it doesn't seem to matter if you cap the lines off. Coolant will still flow at the rear of the head, it's not like it will dead end at the cap. How hot are we talking when you say heating up? I live in Phoenix so I know heat just as well as you do. 220 degrees on the gauge is nothing abnormal. My stock gauge will begin to rise if I drive with the AC on more than about 75 MPH when it is effing hot outside, if I slow down it seems to reduce the load on the engine a lot and temps come down a bit. I have the under tray and all shrouding in place etc with a thick Koyo radiator, and I have a 4.3 rear end too with a W58, so 65mph = 3000 rpm.

 

[Devin LeBlanc]

Im having the same issue. It will get up to 220 but then start creeping if I don't shut the A/C off.

 

[IJ.]

IJ, That is about the only thing I don't have. I heard Toyota still has them for like 70.00.. Might end up picking one of those up!

It's worth 5>8c @ 65 Mph, not sure what would happen if you kept driving as I always went home and put mine back on or bolted it up properly if the car had been to a shop for work or a bud had "helped with the assembly...

 

[Turbo Habanero]

what do you mean by undertray? just curious

 

[Devin LeBlanc]

There is a plastic under tray to direct airflow. 95% of old cars don't have them because they were either taken off and never put back on, or broke and fell off in the road.