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Old 05-13-2018, 10:51 AM   #1
Booki
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Default Car running HOT - 105c/221F. Cools down when rpm's rise. Bottom of the rad stone cold

Not sure whats up with my cars temps - It hasn't "overheated" yet but have been monitoring the temps via my OBD2 gauge.

Highest its seen is 105c when cruising at about 100km/h - not towing, no hills just flat road!

I noticed if i clutch in and give the car a bootful of revs the temps start to come down! Same if i downshift a gear and get the rpm's higher.

The top radiator hose is super hot - the bottom radiator hose is freezing in comparison. Its stone cold. - So my current thoughts are the thermostat is not opening because the coolant around it is cold?

I don't understand how the hot water cannot get down to the bottom of the rad and start circulating the coolant around, especially at such high temps!

The radiator is a full thicker aluminium eBay special - Its about 6 months old. Could it be stuffed already?
Is there a way to "test" the radiator in terms of flow?


Things to note;

Brand new EJ257 short
Reco Heads
New Water Pump
New Thermostat
Have ran the car to operating temp with the cap off and a spill free funnel with coolant to purge the air - Heater works, believe there are no air bubbles.

I currently have the radiator out of the car at the moment and gave it a flush with the hose - nothing abnormal came out. Placed it on my bench top which is flat - poured in some boiling water from the kettle and felt around. Poured it in from the hot side and noticed that the bottom of the rad was still cool. Not very scientific but yeah just spit balling here
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Last edited by Booki; 05-13-2018 at 11:02 AM.
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Old 05-13-2018, 11:11 AM   #2
Charlie-III
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With the rad out, run water backwards through it to see if anything comes out.

If the rad is flowing, then thermostat or pump. Yes, most of your major parts are new.
An IR temp gun can be helpful here.

The higher revs may be overcoming an issue (rad clog, thermostat, pump) but you need to find it.
Running hot may be adding to your smoking.
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Old 05-13-2018, 11:16 AM   #3
Booki
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Quote:
Originally Posted by Charlie-III View Post
With the rad out, run water backwards through it to see if anything comes out.

If the rad is flowing, then thermostat or pump. Yes, most of your major parts are new.
An IR temp gun can be helpful here.

The higher revs may be overcoming an issue (rad clog, thermostat, pump) but you need to find it.
Running hot may be adding to your smoking.
Thanks for the tips!

Is there a easy way to diagnose a bad pump? I had a look at the blades with my inspection camera and it looked all good inside. It also doesn't leak.

Also water does flow from one end to the other when its upright and I run some garden hose water through it....is that indicative of anything or will a "clogged/blocked" rad still do that?

Last edited by Booki; 05-13-2018 at 11:22 AM.
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Old 05-13-2018, 10:12 PM   #4
Charlie-III
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A couple times I have had new pumps have the blades spin on the shaft, thus no pumping.
Old pumps have corroded the blades off, not likely your issue.

With a thermometer, a pan of water on the stove, dangle the thermostat in the water and heat it, see if it opens fully.
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Old 05-13-2018, 10:12 PM   #5
Charlie-III
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A good sized funnel and a bucket of water, pour into the radiator, should flow fast. A hose may not get a high enough volume all at once.

Last edited by Charlie-III; 05-13-2018 at 10:20 PM.
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Old 05-13-2018, 10:14 PM   #6
Booki
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Quote:
Originally Posted by Charlie-III View Post
A couple times I have had new pumps have the blades spin on the shaft, thus no pumping.
Old pumps have corroded the blades off, not likely your issue.

With a thermometer, a pan of water on the stove, dangle the thermostat in the water and heat it, see if it opens fully.

Thanks charlie - I did try that with the thermostat and it opened up no problems.

Interesting to hear about the blades, I did check mine with a inspection camera and rotated the crank - the blades do move.


My current theory is that the thermostat is not opening - but not because its failed or doesn't work. But because the surrounding coolant is not hot/warm to get it to open.

Which really only leaves poor flow from the radiator or a poor performing pump.

Last edited by Booki; 05-13-2018 at 11:21 PM.
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Old 05-14-2018, 12:23 AM   #7
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Quote:
Originally Posted by Booki View Post
Thanks charlie - I did try that with the thermostat and it opened up no problems.

Interesting to hear about the blades, I did check mine with a inspection camera and rotated the crank - the blades do move.


My current theory is that the thermostat is not opening - but not because its failed or doesn't work. But because the surrounding coolant is not hot/warm to get it to open.

Which really only leaves poor flow from the radiator or a poor performing pump.
Itís not flow from the radiator that opens the thermostat, itís flow from the bypass circuits. The heater is one of them, the turbo reservoir return is one, and I think the oil cooler return is one. Make sure those circuits are all open with no kinked hoses or anything.
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Old 05-14-2018, 12:35 AM   #8
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Quote:
Originally Posted by takotruckin View Post
It’s not flow from the radiator that opens the thermostat, it’s flow from the bypass circuits. The heater is one of them, the turbo reservoir return is one, and I think the oil cooler return is one. Make sure those circuits are all open with no kinked hoses or anything.
Hmmm - that makes more sense. Naturally the bottom of the rad would be cold then as it dissipates the heat. So there is no cooling getting to the thermostat via those lines?

I thought the thermostat got its heat from the radiator itself to open up. I will have to follow those hoses to make sure they are connect correctly.

I don't believe my model has a oil cooler, but will look into those other circuits.

I have put in a throttle body hose delete - capped off the ends that go to the throttle body, would this make a difference?
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Old 05-14-2018, 12:41 AM   #9
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Quote:
Originally Posted by Booki View Post
Hmmm - that makes more sense. Naturally the bottom of the rad would be cold then as it dissipates the heat. So there is no cooling getting to the thermostat via those lines?

I don't believe my model has a oil cooler, but will look into those other circuits.

I have put in a throttle body hose delete - capped off the ends that go to the throttle body, would this make a difference?
Coolant does flow through the radiator and through the thermostat once it opens. Before the thermostat opens it needs hot coolant flowing behind it to heat it up. I donít think the throttle body would make a difference, but Iím not sure.

The one I have seen a few times is the little elbow hose at the thermostat housing.
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Old 05-14-2018, 12:46 AM   #10
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Originally Posted by takotruckin View Post
Coolant does flow through the radiator and through the thermostat once it opens. Before the thermostat opens it needs hot coolant flowing behind it to heat it up. I donít think the throttle body would make a difference, but Iím not sure.

The one I have seen a few times is the little elbow hose at the thermostat housing.
I have recently changed out a turbo on the car, so I will have to double check those lines and look for anything odd.

I hope its as simple as kinked hose!
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Old 05-14-2018, 08:53 AM   #11
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Quote:
Originally Posted by takotruckin View Post
Itís not flow from the radiator that opens the thermostat, itís flow from the bypass circuits. The heater is one of them, the turbo reservoir return is one, and I think the oil cooler return is one. Make sure those circuits are all open with no kinked hoses or anything.
Agreed.
Also, is the thermostat in correctly? The coil part needs to be in the engine and the "wiggle valve" either forward or up depending on how it installs.
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Old 05-14-2018, 09:00 AM   #12
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Originally Posted by Charlie-III View Post
Agreed.
Also, is the thermostat in correctly? The coil part needs to be in the engine and the "wiggle valve" either forward or up depending on how it installs.
Thermostat is in correctly, coil section is inside the engine and the jiggle pin is on the top (it can really only go in one way)
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Old 05-14-2018, 09:52 AM   #13
Charlie-III
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Quote:
Originally Posted by Booki View Post
Thermostat is in correctly, coil section is inside the engine and the jiggle pin is on the top (it can really only go in one way)
Juuuust checking.......
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Old 05-16-2018, 10:40 AM   #14
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Havn't had a chance to troubleshoot the cooling system yet - cars just been sitting there....

Anybody else have any tips on what it could be?
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Old 05-16-2018, 02:21 PM   #15
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Have you burped the coolant system properly?
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Old 05-16-2018, 06:37 PM   #16
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Have you burped the coolant system properly?
Yes, I kept the car running, cap off with the funnel attached.

That said I have purchased a vacuum fill tool and will be using that
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Old 05-17-2018, 04:57 AM   #17
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have you done a block test?
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Old 05-17-2018, 08:18 AM   #18
Booki
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Quote:
Originally Posted by subaru_gc8 View Post
have you done a block test?
No I havn't - But i hope there isn't anything wrong!

I just put in a brand new shortblock from subaru!


That said....my block test kit came in the mail today. Will be trying it out.
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Old 05-18-2018, 03:08 AM   #19
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Quote:
Originally Posted by subaru_gc8 View Post
have you done a block test?
Block test done.

Didn't indicate anything. Fluid stayed the same color.


This car


What would cause the thermostat not to heat up?
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Old 05-18-2018, 05:49 AM   #20
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Your temp sensor could be bad.. located behind your alternator...of thats giving you a bad temp read then it will throw incorrect readings. Im guessing u have no coolant leaks or coolant mysteriously disappearing or that would be most likely head gasket leak. If all those check out and u did everything u said u did correctly, including thermostat right side up, then you're not bleeding it properly
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Old 05-18-2018, 07:45 AM   #21
Booki
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Thought about the temp sensor, but I don't think its lying. My thermostat should at least be opening and allowing coolant to circulate
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Old 05-18-2018, 09:40 AM   #22
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Quote:
Originally Posted by Andrew2166 View Post
Your temp sensor could be bad.. located behind your alternator...of thats giving you a bad temp read then it will throw incorrect readings. Im guessing u have no coolant leaks or coolant mysteriously disappearing or that would be most likely head gasket leak. If all those check out and u did everything u said u did correctly, including thermostat right side up, then you're not bleeding it properly
Quote:
Originally Posted by Booki View Post
Thought about the temp sensor, but I don't think its lying. My thermostat should at least be opening and allowing coolant to circulate
One way to sorta test temp sensors.......in the morning (after car has sat), bring up realtime data on a scanner.
The ECT and IAT should be about the same as ambient temp. The ECT can be the ECU data as well as the dash gauge.
You can also wiggle connections while watching the data to see if it changes.
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Old 05-18-2018, 09:57 AM   #23
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Thanks Charlie, I did notice this as I have both those readings on my PLX OBD gauge.

They are both pretty similar and don't seem to be off.
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Old 05-18-2018, 01:13 PM   #24
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Bad temp sensor would not explain the cold lower hose, though...

"Lazy" thermostat???

<-----suffering from the same symptoms
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Old 05-19-2018, 06:51 AM   #25
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OK, I did some work on the car today - the issue seems resolved so far.

What I did was -

* Drain my coolant.
* Take off the hoses to the heatercore, water pump housing (the bypass hoses) followed them through and flushed them with the garden hose sprayer and compressed air.
* Flushed the water lines on my turbo (TD04)
* Removed the shielding on one of the water hoses for the turbo, Its a generic piece I had but suspected it might have kinked the hose (might not have, but the turbo is coming off once I verify my cooling system is alright)

I Vacuum filled the system with water for testing and so far - no issues.

Thermostat is opening, bottom hose gets warm when appropriate.

If I don't have any water missing from the overflow - Its happy days!
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