Considerations related to H6 head gaskets and cooling system

Posts specific to the 3.0 litre NA H6 engine

Re: Considerations related to H6 head gaskets and cooling sy

Postby subyroo » Sat Nov 14, 2020 9:52 am

nvmylh wrote:Since then I haven't had any issues, the temp gauge does move very slightly but no where near like it did before and so far I have not lost any coolant from the overflow bottle. Also the heater works fine.

Does anyone else's temp gauge (EZ30's) move at all when driving?


I was advised by my Subaru workshop to not rely on the OEM Temp gauge, by the time you see it hit the Red Zone your engine can possibly be toast.
I bought an "el cheapo" corded OBDII reader from UltraGauge to use on my old 2003 XS Forester. Nowadays you can get wireless OBDII readers, might pay you to invest in one. :good:
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Re: Considerations related to H6 head gaskets and cooling sy

Postby bigBADbenny » Sat Nov 14, 2020 6:44 pm

:good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good: :good:

As suggested in the first post :)
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Re: Considerations related to H6 head gaskets and cooling sy

Postby nvmylh » Mon Nov 16, 2020 8:07 am

"move very slightly" does not mean horizontal to red zone! I meant does anyone else's move within like 1 mark above/below horizontal with normal driving or up hills?

Obviously if the gauge heads into the red zone something is seriously wrong.. I've bought a nexus 7 setup and will try to get that installed asap.
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Re: Considerations related to H6 head gaskets and cooling sy

Postby bigBADbenny » Mon Nov 16, 2020 9:02 am

Make sure you bench test the nexus extensively to make sure all the restart & power mgmt features are working.

Setting temp alarm will help you correlate dash temp vs actual/obdii...
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Re: Considerations related to H6 head gaskets and cooling sy

Postby Yowie » Mon Nov 16, 2020 5:25 pm

"move very slightly" does not mean horizontal to red zone! I meant does anyone else's move within like 1 mark above/below horizontal with normal driving or up hills?

Obviously if the gauge heads into the red zone something is seriously wrong.. I've bought a nexus 7 setup and will try to get that installed asap.


It is normal for the coolant temp to change depending on engine load. With my 2.5 litre turbo normal indicated coolant temp is high 80s or low 90s (degrees celcius).

A sustained spirited mountain climb will send coolant temps into the high 90s.

OEM needle-based temp gauges are notoriously inaccurate outside of indicating "cold" "ok" and "hot". Indeed I think some manufacturers deliberately mess with the OEM temp readout so they don't get customer complaints about "it almost overheated when I drove up a mountain". As a result those funky gauges tent to flick straight from "ok" to "overheated".

I'm reading my temps (and oil temp) off a digital gauge attached to the steering column. The coolant temp sensor is plumbed into the coolant path that used to run through the throttle body.

Before I had that I relied on Bluetooth/Torque to display coolant temp. It works well, except when the bluetooth connection drops out and won't re-establish (which Murphy says is at the time you really want to see coolant temp).
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Re: Considerations related to H6 head gaskets and cooling sy

Postby nvmylh » Mon Nov 23, 2020 10:40 am

Hey guys,
Took the liberty for a reasonable 100km drive on sunday, 28-29deg day, mainly down eastlink (a freeway for those not in melbourne), boronia to langwarrin. Had the nexus 7 working well and reading temps etc. Here are some notes:

- cruising at 100kmh, temp sat on 96-97deg. Aircon on or off didnt seem to matter (FYI on flat road I reckon it adds about 0.5l/100km in fuel, cruised at about 8-8.5l/100).
- long slight hills on the freeway saw the temp go up to 100deg
- I noticed that above 100deg the temp gauge started to move from just below horizontal to just above.
- I did 1 decent run up a long hill (ferntree gully rd, between eastlink and jells road). Car kicked back to 3rd (i think), 4000rpm'ish, 85kmh, reasonable load. Temp went up to 103-104 (just near top of hill) and held. Then just at the top of the hill the lights were red so had to stop. Sat idling, I think the temp dropped to 102deg, gauge was slightly above horizontal but as soon as i took off and did a u-turn, it dropped to about 96.
- similar thing happened afterwards in stop-start traffic, temp hit 101-102 i think, but as soon as i started moving it would drop. More revs or kicking back a gear and not loading up at <2000rpm seems to help keep the engine cooler, though uses more fuel. Surely my water pump isn't missing some material off the impeller?

Best thing so far since bleeding the coolant, no coolant has been lost so I'm fairly confident there's no headgasket or heater core issues. Next test might be a higher load test with a trailer or something.

Interested to know other peoples engine temps, or if anyone has tried a slightly lower temp thermostat??
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Re: Considerations related to H6 head gaskets and cooling sy

Postby Yowie » Mon Nov 23, 2020 11:37 am

That seems like a pretty reasonable-looking set of temps under those conditions.
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Re: Considerations related to H6 head gaskets and cooling sy

Postby ifrankenstein7 » Fri Feb 19, 2021 7:43 am

Hi

I recently bought another 2005 Liberty 3.0r with around 175k on the odo. When i got it checked from a mechanic i was told that it had a hg leak and i should just sell the car..
Since im a noob with regards to the technicalities of the engine. i researched as much as possible about hg leaks and symptoms and for all i know theres nothing that matches with the symptoms apart from engine oil leak. The quotes ive recieved so fas if there is a potential hg leak is around 5k (including timing belt, water pump and so on) but for a $6500 car spending 5k seems pretty stupid no matter how much i love the car.

Would appreciate some advice on this please.
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Re: Considerations related to H6 head gaskets and cooling sy

Postby Yowie » Fri Feb 19, 2021 7:59 am

Get quotes on wrecker engines? (obtain and install). For less than $5k it could be worth rolling the dice.
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Re: Considerations related to H6 head gaskets and cooling sy

Postby bigBADbenny » Fri Feb 19, 2021 12:35 pm

From where does the oil leak emanate?
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Re: Considerations related to H6 head gaskets and cooling sy

Postby ifrankenstein7 » Fri Feb 19, 2021 11:54 pm

bigBADbenny wrote:From where does the oil leak emanate?

one mechanic reckons its front main valve cover leak, one reckons its timing cover leaks and around timing cover and one reckons it the hg itself lol
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Re: Considerations related to H6 head gaskets and cooling sy

Postby bigBADbenny » Sat Feb 20, 2021 9:50 am

How bad is it?
You can buy a UV oil dye kit & torch from eBay, clean the area thoroughly and check for the leak source after a drive.
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Re: Considerations related to H6 head gaskets and cooling sy

Postby RX25SE » Sat Feb 20, 2021 3:31 pm

ifrankenstein7 wrote:Hi

I recently bought another 2005 Liberty 3.0r with around 175k on the odo. When i got it checked from a mechanic i was told that it had a hg leak and i should just sell the car..
Since im a noob with regards to the technicalities of the engine. i researched as much as possible about hg leaks and symptoms and for all i know theres nothing that matches with the symptoms apart from engine oil leak. The quotes ive recieved so fas if there is a potential hg leak is around 5k (including timing belt, water pump and so on) but for a $6500 car spending 5k seems pretty stupid no matter how much i love the car.

Would appreciate some advice on this please.


Is the car overheating or loosing any coolant?
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Re: Considerations related to H6 head gaskets and cooling sy

Postby ifrankenstein7 » Wed Feb 24, 2021 3:43 am

RX25SE wrote:
ifrankenstein7 wrote:Hi

I recently bought another 2005 Liberty 3.0r with around 175k on the odo. When i got it checked from a mechanic i was told that it had a hg leak and i should just sell the car..
Since im a noob with regards to the technicalities of the engine. i researched as much as possible about hg leaks and symptoms and for all i know theres nothing that matches with the symptoms apart from engine oil leak. The quotes ive recieved so fas if there is a potential hg leak is around 5k (including timing belt, water pump and so on) but for a $6500 car spending 5k seems pretty stupid no matter how much i love the car.

Would appreciate some advice on this please.


Is the car overheating or loosing any coolant?


in about a month it has lost about two lids (coolant bottle lid as a reference worth of coolant), it loses more engine oil than anything
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Re: Considerations related to H6 head gaskets and cooling sy

Postby bigBADbenny » Wed Mar 03, 2021 4:42 pm

As long as it isn’t oil into coolant or vice versa.

You can always do a TK test for combustion gasses in the coolant.

If I had an H6 I’d do the full coolant bleed once a week for a few weeks, then monthly, then quarterly and so on.

Just to get an idea of how often they actually require bleeding.
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