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Discussion Starter · #1 ·
Hi SF Team,

In diagnosing why my coolant temp keeps rising (during idle) after installing new oem Thermostat + new Koyo radiator + new generic water pump, I noticed the lower radiator hose stays cold to the touch.

So, this tells me something is impeding coolant flow. Has anyone had a new water pump (generic brand) fail after install in such a way that it does not leak but also does not push enough coolant through the system?
 

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Mind if I do a J?
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Did you burp the system correctly?
 

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This happened to me way back on my Tacoma. Turns out, I put my thermostat in backwards.

Sent from my SM-G950U1 using Tapatalk
 

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Only thing I can think of is the teeth on the gear are sheared off.
 

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I just had a similar issue after putting in a new radiator/cap/hoses/tstat, turned out to be a bad thermostat right out of the box.

Edit: This was with an aftermarket thermostat from a big box store though, not an OEM one.
 

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From the land down under
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I know this wont help your diagnosis, but when it comes to water pumps and thermostats, I always buy OEM....the price difference just doesnt stack up for me.

I would remove the thermostat and test it in a bowl of hot water, to visually confirm that it opens

GL
 

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Discussion Starter · #10 · (Edited)
Hi guys,

Thermostat is a new oem Toyota/Lexus one, but water pump I don’t remember the brand. Previous old oem thermostat worked fine, but I changed it to this new one during this diagnosis process.

I bought a new oem water pump and I’ll be able to compare it to the installed one (in attached picture) tomorrow. This is a 2JZ-GE motor that I turbocharged.

The drive belt configuration looks correct and I flushed coolant through the new Koyo radiator and longblock before installing everything back together. The fluid flowed freely through long-block and radiator with no signs of clogs/blockage. I also want to install a coolant-pressure sensor somewhere in the system just to be extra sure it’s not losing any pressure when the engine is warm. Strange thing is, I’m not losing any coolant. Where would you guys install this coolant pressure sensor?
 

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Just to confirm..did you bleed it with a no-spill funnel? The MKIV loves to trap air bubbles in the heater core. Took me an extra 20 minutes of revving the motor between 1k and 2k RPM, with the front of the car elevated above the rear, to finally get the bubbles out.

Regarding the water pump.. with everything installed back on the car, did you have coolant flow at the top of the radiator with the cap off?
 

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Discussion Starter · #12 ·
Just to confirm..did you bleed it with a no-spill funnel?

Regarding the water pump.. with everything installed back on the car, did you have coolant flow at the top of the radiator with the cap off?
Yes to both questions. When I started the car with radiator cap removed, I noticed the coolant level in the radiator would slightly go down once the car was around 170-180 degrees F. So, maybe the water pump is not flowing enough or there is some blockage in the cooling system?

It passed the blown-headgasket chemical test with that glass vile attached the radiator fill port. The blue liquid turned slightly lighter blue color, but never turns yellow (BHG).
 

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Discussion Starter · #13 · (Edited)
FML…Fedex keeps showing the H2O pump delivery as being delayed. So, I’m thinking of drilling a 4mm hole in the outer brim of the thermostat. It seems to help with burping air bubbles out the system.

I got the idea from here at the 12:50 mark:

My idea is to just drill 1 hole like this oem Lexus thermostat to see if it helps:

What do you guys think? Has anyone tried drilling a hole (or holes) in their thermostat?
 

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Discussion Starter · #14 ·
This happened to me way back on my Tacoma. Turns out, I put my thermostat in backwards.
. Jaymaal, thanks for sharing your experience with me. I went to double check my thermostat and it was also installed backwards, so you were correct! 😛 Idle Coolant temps are now stable between 175 and 179 degrees Fahrenheit on new oem Lexus/Toyota thermostat. Supraforums FTW!
 
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