Reddit mentions: The best cooling system additives

EDIT: I just realized the picture shows the OIL CAP. I thought it was the Radiator cap when I glanced at first. Oh well... I'll leave the post anyways, perhaps it helps someone with cooling issues. OP: I never dealt with that problem. Definitely looks like cross contamination with coolant. But if that's not the case, try looking into a few oil changes (perhaps with low viscosity oil), along with snake oils such as Seafoam and Marvel Mystery Oil. I had very good luck with them in the past. Best of luck.

Hey man, I had a nearly identical issue with my truck and fixed it without too many problems. This is assuming your head gasket is good and you aren't cross contaminating oil and coolant.

Basically it boils down to (te-heee) use of certain old antifreeze products known to cause this as well as products like "stop-leak" and similar. Those products and inadequate cooling system maintenance can cause this problem.

You will need a flush kit, along with a few bottles of cleaner. You can get both at Walmart cheaper than Amazon. Get also 5-6 gallons of distilled water.

Install the flush kit on the heater core hoses as described in the instructions. If you have trouble determining which is the hose going into the heater core, turn on the car (ensure heat is off) and touch both heater core hoses as it warms up. The one that stays cold is the outlet.

Flush the system with the garden hose as described in the instructions. The first few times you do it you will see a ton of crap coming out. Flush for a few minutes, then turn off the hose and let the water drain for a bit. Close the drain plug and flush cap, empty one bottle of cleaner in the radiator, top it off with distilled water, close fill cap. Drive the car for a few days.

Repeat the above process 5-6 times every few days until the flush water coming out is completely clean and you no longer see baby-shit accumulating under the radiator cap.

Once you have done a couple of rounds and the coolant water is reliably clean (no traces whatsoever of that crap), do a few rounds of distilled water only (to remove all traces of cleaning agent). Then go ahead and fill it up with good quality antifreeze compatible with what's recommended for that vehicle.

Keep in mind that antifreeze is needed for multiple reasons, including lubrication. Just because it's summer and you don't run the risk of coolant freeze, keep in mind that during the above process you will be running the water pump without lubrication. Since it seems like it's your daily driver, you should be able to do the whole process in the span of a couple of weeks without issue.

Good luck and report back with your findings.

You're getting ripped off at $2000, so $3,000 is astronomical.

My local subaru shop "not a dealer" does HG replacements starting at $900. There are often a few extra parts needed, so it can go up to $1,300, but that isn't often. They do great work and specialize in Subaru... I'm sure there is a similar shop in your area

With a new HG and some Subaru Coolant System Conditioner it should run 200,000 MORE miles.

Honestly, if you picked up a Subie with 78K for less than $3k, boy did you score... It's totally worth the REASONABLE HG replacement.

That seems like a better option than taking apart a dashboard or throwing down a grand for this.

Have you ever used any of those additives that seal leaks on their own? I'm hoping to just have a fix hold me over until after winter at the latest.

Something like these: https://www.amazon.com/K-Seal-ST5501-Purpose-Permanent-Coolant/dp/B001QT9KO6

http://barsleaks.com/product/liquid-aluminum-cooling-system-stop-leak/

Not low on coolant √ So that sounds promising. I already have a new thermostat and will replace tomorrow. I just didnt want to drain the whole system again. Is the Subaru Coolant Conditioner something I should add as well?

Will check on the heater core hoses and update.

Thanks so much for your help!

You're not wrong.

Definitely sounds like K-Seal will have a high chance of fixing it though. Shake first, then pour, then enjoy the time and money saved.

https://www.amazon.com/K-Seal-ST5501-Purpose-Permanent-Coolant/dp/B001QT9KO6/ref=sr_1_1?keywords=kseal&qid=1568304202&s=gateway&sr=8-1

Nice! As preventative maintenance Subaru sells this stuff. It is rebranded Holt's Radweld. Small bottle. I threw some in my daughter's Subie just in case. Can't hurt I guess. If the headgaskets on the replacement motor were original units then it is probably just a matter of time before they go too. But, you never know. This magic Subie juice is supposed to help.

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https://www.amazon.com/Subaru-SOA635071-Coolant-System-Conditioner/dp/B00IGZP2UE/ref=sr_1_3?crid=3GZ6ZTJOIDK4X&keywords=subaru+radiator+conditioner&qid=1554864612&s=gateway&sprefix=subaru+radiator+%2Caps%2C328&sr=8-3

ez fix, buy one of these kits: http://www.amazon.com/Prestone-AFKIT0-Universal-Flush-Fill/dp/B000CCFY5W/ref=sr_1_9?ie=UTF8&qid=1323365128&sr=8-9
flush system out and run water from hose threw motor while running for like 20 minutes good to go, ditched the dex cool out of my saab with a similar kit. cheap and sold everywhere

If you don't have record of the last time the coolant was changed, change it. To play it safe I'd use Subaru Super Coolant (blue) with Subaru Cooling System Conditioner (Holts Radweld).

In the event you need to do the head gasket, Speed Academy has an amazing video I used to do mine.

• Subarus tend to be easy to fix when they break. I have an '09 2.5i SE 5MT and I didn't even have to remove the hood to remove my engine.
  
• Make sure whatever brand you use the new gaskets are MLS (multi-layer steel). As they are regarded in the community I used Six-Star Bernie.
  
• If I had to do it again I would have used ARP studs to fasten my heads to the block.
  
• Machine shop labor is cheap. Take your heads to one to have them professionally-decked.
  
• When torquing the head studs into the block, find the Subaru directions (i.e., Mitchell1) and *follow them to the letter*. You're going to be turning them, backing them off, turning them again and whatnot. Just go with it.
  
• "As long as ya got it outta there" you can change these things as well:
  
  • Timing belt & pulleys, thermostat, water pump (Aisin / "eye-shin" sells a reasonably-priced kit)
    
  • Coolant hoses
    
  • Spark plugs
    
  • Engine oil and filter
    
  • Oil pump
    
  • STi engine mounts (left, right)
    
  • *RECOMMENDED* oil pickup (the OEM one tends to crack, starving your engine of oil)
    
  • *RECOMMENDED* timing belt guide (as the stamped OEM one failed when my engine blew, I replaced it with a Tomei milled one)
    
    Call me crazy, but when I blew my engine I elected to keep the car. Subaru has engineered a family sedan way better than it has to be for the market and it shows.
    
    I need to do some digging to find the invoices of parts I purchased; I'll update this reply as I find them.

One easy potential repair is adding a sealant to your radiator. It doesn’t work on all head gasket issues, but it does work on some (at least for awhile) and could extend the useful life by a bit.

This stuff sealed a radiator (non head-gasket) leak for me and there are reviews and videos of it fixing leaks in the head-gasket as well.

Fascinating. I'm wondering if Subaru recommends and approves only one type of "stop leak", something they call a coolant conditioner, such as this, https://www.amazon.com/Subaru-SOA635071-Coolant-System-Conditioner/dp/B00IGZP2UE

This:

https://www.amazon.com/Cummins-3376891-Oil-Additive-Fluorescent/dp/B003X2ZZPM

Black light oil additive will help you track down where it's coming from.

A few different colours will help, if it's Engine oil or ATF, or power steering...

You can run a coolant that has SCA's already in it or you can just run standard coolant and buy the SCA separate and add it yourself. You need to check the concentration regardless to make sure it is still good. They sell kits with litmus paper and a gauge to check concentration. Genuine Ford Fluid VC-8 Diesel Cooling System Additive - 16 oz. https://www.amazon.com/dp/B000NU3LPS/ref=cm_sw_r_cp_apa_i_yUeYCbFY5JCE8

Do you have a small leak anywhere, and was the water pump changed the last time the timing belt was done? As others have mentioned the thermostat is a good place to start. Also Subaru makes a coolant conditioner that should be used when not using genuine Subaru coolant. It's a small bottle that can easily be found on Amazon here: https://www.amazon.com/Subaru-SOA635071-Coolant-System-Conditioner/dp/B00IGZP2UE

Doesn't get any better than royal purple, nice choice. I would still recommend a friction modifier, but if you wheel and have to flush the diff out often maybe just skip it. If you don't, and just do normal service this stuff goes in my 67 Jeep front and rear LSD diffs, the rear of my 98 ZJ and my LJ (has air lockers but I add anyway, doesn't hurt)

It's real quality stuff and will prevent it from chattering, one bottle per axle

>I have a good knowledge of car maintenance but have never owned a 4wd before.

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I have a 1994 Jeep Grand Cherokee 5.2V8, NP249J transfer case, Dana30 front diff, and ?Dana44A rear diff? still not 100% sure about the rear diff model


1994 would have a d35


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If I use this Lucas gear oil 75w-140 Synth, which says excellent for limited slip use, do I still need to add this additive when I service the differentials?


That'll be fine, no need for an additive.

>
Also ATF+4 in the transfer case?


Dex/merc or atf+4. The tcase isn't picky.

>
How do I tell if my Viscous coupler is bad? Recommendations if it is?


I think the test is to turn in a tight circle and if you feel binding it's bad. Recommend a 231 or 242 swap.

Did you change out your coolant with Subaru coolant and put in the Subaru coolant conditioner after your head gasket job? The conditioner is very important.

Example:
http://www.amazon.com/Subaru-SOA635071-Coolant-System-Conditioner/dp/B00IGZP2UE

its the clutch packs in the axle from the quadra drive system. you either need to add friction modifier https://www.amazon.com/Genuine-Mopar-4318060AC-Limited-Additive/dp/B000TTEX8W. I had to do a full fluid change I used royal purple 75W140 with limited slip addative, as well as a little extra mopar addative. sound went away

http://www.amazon.com/Subaru-SOA635071-Coolant-System-Conditioner/dp/B00IGZP2UE

I assume you're from germany because you linked german wiki so you probably already found out that MT-90 isnt available in europe. I used this and this in my NC which had the same issue and it made shifting when cold so much better

I went out and bought one of these Prestone Flush 'N Fill Kits and followed the directions in this XJTalk thread.

You could do that several times if you wanted to. It would take more than a gallon though. This is what you need.

Seems like those Gen 1 cruzes had a lot of engineering problems with them. Have a 2015 Cruze L myself; had a "slight" bit of the same problem, but it was just a loose gasket that easily fixed by adding some of this, https://www.amazon.com/Bars-1150-Cooling-System-Repair/dp/B00753MZWG/ref=sr_1_16?keywords=bars+stop+leak&qid=1555949124&s=gateway&sr=8-16

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I would give it a try. If it doesn't work, you are going to likely bring it to a chevy dealership.

Maybe a sealant can help you for a while, but given the amount you're losing I bet it's a big leak.

Something like this:
https://www.amazon.com/K-Seal-ST5501-Purpose-Permanent-Coolant/dp/B001QT9KO6