Author Topic: Overheating at idle or low speed 2011 STi built engine  (Read 1496 times)

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Offline Gqshiftdrift

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Overheating at idle or low speed 2011 STi built engine
« on: June 20, 2018, 05:19:30 pm »
Here's the issue the car over heats when its not in motion, it does this randomly, its happened after going for a fun drive or just puttering along in regular traffic. When it does try to overheat the coolant fills the overflow tank and doesn't suck back into the cooling system. The radiator stays full but the top part of the system where the second rad cap is needs to be topped up when this happens. It ran for about a year and a half without issue other than a misfire issue that has come and gone. In the last 6 months I've had it looked at by a dealership 3 times without any success of solving the issue, they want to pull the heads to see if there is something wrong inside they can't diagnose. 

I have replaced the thermostat, both rad caps and the coolant. The coolant that came out when the t-stat was replaced was as blue as it is new from the jug, no crud, gunk or grit came out of the rad when the system drained. There is no coolant in the oil or vice versa, it starts and drives just fine with out any other problems just this overheating issue that nobody can point a firm solution at. All oil changes are done with Amsoil filters and signature series oil at about 5000km intervals. Oil is sent off for analysis and the reports come back good with little fluctuation in the tests from one to the other.

I had all the below work done between the fall of 2015 and spring 2016 now have 30000km on the car since the rebuild and tune:
-Techworks Engineering engine build- new crank, rods, pistons, bearings, 5 angle valve job, springs and retainers, valves, valve guides, lifter buckets, oil pump upgrade, new timing set, plugs, multi layer steel head gaskets and EGR delete
-Airboy tuning Dyno tune after break in was completed for husky 94 fuel
-Killer B windage tray and oil pickup tube
-OS Giken Grand Touring twin plate clutch + aluminum flywheel
-Kartboy short throw shifter
-Whiteline swaybars and endlinks and steering bushing kit
-2015+ STi steering rack upgrade
-DBA 4000 rotors front and rear with Endless racing MX72 pads all around
-Stainless steel brake lines all around
-Gramlight 57DR 18x9.5 +40 wheels all around with 265/35zr18 BFG sport comp 2 tires
-Tomei equal length header with up pipe ceramic coated
-Cobb catted Down pipe, Cold air intake with box, turbo heat shield and v2 Accessport
-Perrin Turbo inlet tube

Looking for anyone who's had a similar issue to resolve and what you had to do to solve it. Considering the engine was fully built and is rated for far more than the factory turbo and fuel system can throw at it I'd be very surprised if the heads need to be done already. I'm not ruling that out as a possible problem at this point, just hoping there is something else to look into first to resolve this problem. Sorry for the long post just figured it would be better to give as much info relating to the problem as I can. Thank you all and have a good one.



Offline SingallZ

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Re: Overheating at idle or low speed 2011 STi built engine
« Reply #1 on: June 20, 2018, 05:59:39 pm »
Maybe either a bubble in the system, broken fan relay, spotty fan wiring or temp sensor, but most likely a blown head gasket. More boost does make blowing a head gasket more likely.

Coupe of questions for you: Does this happen in cold weather? Do you ever hear the fans going? Does it drink coolant? Does it have steam coming from the tail pipe? If yes to the last two then even greater chance of a blown head gasket.

Offline Gqshiftdrift

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Re: Overheating at idle or low speed 2011 STi built engine
« Reply #2 on: June 21, 2018, 11:57:22 am »
Thanks for the input.
It has been pressure tested at Subaru and they told me it holds 15 psi with out issue.
I do hear the fans kicking in and out thou perhaps testing them to ensure they are working properly is worth looking into.
This has happened in cold weather and warm weather
When it does get hot it fills the overflow tank which I put back into the top of the system as a temporary fix after each incident.
The oil doesn't test positive for coolant when the oil analysis is done by Agat labs.
It does have a little steam on start up but it has always had a little even before the engine was done. 

Offline Asstuna

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Re: Overheating at idle or low speed 2011 STi built engine
« Reply #3 on: June 21, 2018, 12:41:03 pm »
My WRX used to leak exhaust into the coolant mostly under boost, which I surmise is the heads lifting off because the studs were aged and stretching. I didn't see mention of it, but get a combustion leak test done on your radiator. You have very similar symptoms to my blown head gasket other than it seems odd to be happening at idle/low revs.

Have you refilled the system and brought it up to temp with a radiator funnel on the upper reservoir? ie. burping it properly.

Do you have the right caps in place? Round, higher pressure on the rad and the lower pressure cap with "ears" on the upper reservoir.

edit::
http://www.westernsubaruclub.com/smf/index.php?topic=40639.msg538786#msg538786

Offline Jay89

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Re: Overheating at idle or low speed 2011 STi built engine
« Reply #4 on: June 21, 2018, 01:36:00 pm »
Check in between your condenser and radiator. You might have a bunch of crap stuck in there plugging it up, and have a lack of airflow. I see this happen all the time on bmws, and porsches.

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Offline darthekai

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Re: Overheating at idle or low speed 2011 STi built engine
« Reply #5 on: June 21, 2018, 02:52:44 pm »
what jay said, but also could be the fans. If temperatures are being reported accurately (ie the temp sensor is good), the fans should run the whole time the thing is overheating.

What does the temp gauge say when this happens?

Another little thing to watch out for, try replacing the drop straw that goes into the overflow tank. If this has a crack in it or isnt seated properly or doesnt go as far down as it needs to, it can cause air to be sucked into the system which would build up in the upper res and might also CAUSE the overheating (by getting trapped in an elbow or coolant passage somewhere).
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Offline Gqshiftdrift

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Re: Overheating at idle or low speed 2011 STi built engine
« Reply #6 on: June 25, 2018, 07:36:30 pm »
My WRX used to leak exhaust into the coolant mostly under boost, which I surmise is the heads lifting off because the studs were aged and stretching. I didn't see mention of it, but get a combustion leak test done on your radiator. You have very similar symptoms to my blown head gasket other than it seems odd to be happening at idle/low revs.

Have you refilled the system and brought it up to temp with a radiator funnel on the upper reservoir? ie. burping it properly.

Do you have the right caps in place? Round, higher pressure on the rad and the lower pressure cap with "ears" on the upper reservoir.

edit::
http://www.westernsubaruclub.com/smf/index.php?topic=40639.msg538786#msg538786 


When the engine was built all the fasteners for the heads were replaced with ARP studs and nuts, Its possible i got a bad one or two in the set. At this point I'm not ruling anything out that could be the cause. I had centaur pressure test the system after replacing both rad caps and the thermostat myself and putting fresh coolant in it. Both caps are on in the right location, checked the manual to be sure. Thanks for the thoughts on this I'll add it to the list of things to try and rule out.

Offline Gqshiftdrift

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Re: Overheating at idle or low speed 2011 STi built engine
« Reply #7 on: June 25, 2018, 07:40:48 pm »
Check in between your condenser and radiator. You might have a bunch of crap stuck in there plugging it up, and have a lack of airflow. I see this happen all the time on bmws, and porsches.

I've been told that subies come with something similar to the bar's leak in the coolant system from the factory and it can cause this kind of issue if it settles in a bad spot. I'll be putting this on the list with the other suggestions to look into. The condenser was replaced 2 years ago and who knows if there is something from the install thats taken this long to surface as a problem. Thank you  :)

Offline Gqshiftdrift

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Re: Overheating at idle or low speed 2011 STi built engine
« Reply #8 on: June 25, 2018, 07:48:09 pm »
what jay said, but also could be the fans. If temperatures are being reported accurately (ie the temp sensor is good), the fans should run the whole time the thing is overheating.

What does the temp gauge say when this happens?

Another little thing to watch out for, try replacing the drop straw that goes into the overflow tank. If this has a crack in it or isnt seated properly or doesnt go as far down as it needs to, it can cause air to be sucked into the system which would build up in the upper res and might also CAUSE the overheating (by getting trapped in an elbow or coolant passage somewhere).

I would hope that while it was at the dealership they tested and checked these things out but I am not 100% sure if they did or not. Having read your post makes me wonder about the temp sensor. When the car does try to overheat I'm always at a light or stop sign not moving, once i start moving and get some air moving the temps come down to normal. I also turn the heat on full blast and roll down the windows to let any extra that i can out of the hvac system.

I'll have to look at the drop straw you mention and see if its fubar or not. I just hit 30 k on the engine and am running a stock turbo and fuel system, Its hard to think the heads could be leaking this early on. I'd much rather a new hose in the overflow tank than having to have the heads done again. This is going to the top of the list as it seems pretty easy to check out if it is failed. Thank you !

Offline RockThePylon

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Re: Overheating at idle or low speed 2011 STi built engine
« Reply #9 on: June 25, 2018, 11:01:58 pm »
Overheating at idle/low speed is textbook fans not working.

In my experience, rad fans at full tilt are roughly equivalent to 30km/h worth of airflow.
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Offline Delphiwrx

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Re: Overheating at idle or low speed 2011 STi built engine
« Reply #10 on: June 26, 2018, 08:10:47 am »
See if you're getting bubbles coming up in your overflow tank. At idle and just after driving.
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Offline tracker

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Re: Overheating at idle or low speed 2011 STi built engine
« Reply #11 on: June 26, 2018, 11:28:08 am »
I had a legacy 2000 that did that after a spirited Snow AutoX where the engine bay was filled with snow...

Blocked the fans and blew the fuses (2 IIRC). It would drive fine but started to overheat when stopped.

Simple as that. Check the fuses and see if the fans come up when the temperature rises.
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Offline Gqshiftdrift

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Re: Overheating at idle or low speed 2011 STi built engine
« Reply #12 on: August 10, 2018, 04:48:43 pm »
Thank you everyone for the input. So after having the coolant tested it failed the combustion gas test. My tech pulled the heads and found the head gaskets failed, sadly with less than 30000km on the engine build. Luckily the heads are still flat and the block face is also flat so they can be replaced without a full tear down and rebuild. Super annoying to deal with for the last year but at least its getting fixed and will be more reliable (hopefully) moving forward. 

Offline mojikita

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Re: Overheating at idle or low speed 2011 STi built engine
« Reply #13 on: August 10, 2018, 05:22:20 pm »
At one point, I did quite a bit of looking into torque procedures for stock bolts and ARP studs. I found this NASIOC post.

Quote
The factory procedure has a re-TQ in it. The ARP instructions do not have this. If you use the ARP instructions you will ALWAYS have HG failure within 20,000~30,000 miles, if not sooner.

https://forums.nasioc.com/forums/showthread.php?t=1451471

Re: the stock bolts, post 11 is a piece of advice I've followed several times and never had a problem.

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Re: Overheating at idle or low speed 2011 STi built engine
« Reply #14 on: September 10, 2018, 04:17:30 pm »
Theres some inflammatory stuff in there but the most important point is "follow the instructions" which in the case of ARP means 3 step torquing the bolts then loosening them off three full cycles before final torque.
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