Blown Head Gasket ?? [HELP NEEDED]

[A90MT]

Hey guys,

So, I'm thinking I may have a blown head gasket or a cracked cylinder head. If anyone has any other suggestions on what to check before I open this thing up, I'd greatly appreciate it. I'll try my best to keep it short but detailed.

Aftermarket Mod List:
2024 Supra 6MT
Pure 850
Intake
Catless DP
Chargepipe
Bootmod3
26-28 PSI
Approx 520-550whp

One night after a car meet ended, I started the car and loads of white smoke started pouring out. Not super thick, more so transparent white and I could smell coolant. It eventually calmed down and I drove home, the car was running at normal operating temps both coolant and oil. (NOTE: I do have the max cooling mode from bm3 enabled which does seem to help. I tried with it off and was seeing higher 220-230F temps in cold weather)

My first thought was, I blew the turbo.. so, I slapped my stock turbo back in to check and upon start-up had some white smoke but much less. I drove it around abit to burn off any excess that might be inside the exhaust. A week goes by, I'm still having the same issue. I then notice while driving up hills and sometimes when doing a pull, my coolant temp drops from 200F down to 165F and then slowly creeps back up to normal temps again. So, I re-bled the coolant system like 6 times and no luck. (NOTE: My exhaust does sound like it's making bubbles during the bleed procedure. EXHAUST, NOT ENGINE BAY)

At this point, I start diagnosing things further and did the following:

1. Coolant pressure test to 20 PSI and only lost about 0.3-0.5 PSI after about 45 minutes. (Could be normal?)

2. Spark plugs, all normal with minor carbon buildup nothing unusual.

3. Compression test, all passed with great compression, nothing unusual.

4. Pending a block test using the colour changing liquid, waiting for it to arrive. (However, I have no bubbles or anything weird in the coolant reservoir so it seems unlikely but still possible to fail)

Unfortunately, I don't have an air compressor to do a full leak down test but if you guys think it's worth giving it a shot, I'll pull the trigger and do that too.

I should also mention that I recently bought new caps for both coolant reservoirs as I did notice some crustyness there. Didn't fix anything unfortunately.

I am certain there are no external leaks that I can see. Given the smoke, it's gotta be a tiny internal leak somewhere, right? The weird thing is, I can rip the car for 20-25 minutes, park and let it idle and no smoke appears at all. But the drastic coolant temperature fluctuations are still there on up-hills.

Could this be PCV related ? I don't believe my intake manifold is leaking inside because that coolant reservoir is FULL, no issues there. It's just the larger reservoir that loses small amounts of coolant.

I'm new to the B58 world so I'd appreciate any guidance yall can provide.

Thanks for taking the time to read.

Cheers

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[lucky phil]

You need to scope the cylinders after it's cooled down from normal operating temps. There is a failure mode for head gaskets where they seal fine at operating temp but leak into the cylinder during cool down mode. You'll get white smoke and possibly a misfire during a cold start esp after prolonged rest like overnight. Once it's burned off the coolant thats leaked into the cylinder and the engine has warmed up the expansion helps seal up the leak until the next time it cools down and the process repeats.

 

[razorlab]

I then notice while driving up hills and sometimes when doing a pull, my coolant temp drops from 200F down to 165F and then slowly creeps back up to normal temps again.

Normal operating mode. When at high loads, coolant pump control goes into escalation mode to hit a lower target temp and temps drop, then come back up after you let off.

 

[Habu]

Normal operating mode. When at high loads, coolant pump control goes into escalation mode to hit a lower target temp and temps drop, then come back up after you let off.

I always notice that after flooring it.

 

[Habu]

You need to scope the cylinders after it's cooled down from normal operating temps. There is a failure mode for head gaskets where they seal fine at operating temp but leak into the cylinder during cool down mode. You'll get white smoke and possibly a misfire during a cold start esp after prolonged rest like overnight. Once it's burned off the coolant thats leaked into the cylinder and the engine has warmed up the expansion helps seal up the leak until the next time it cools down and the process repeats.

Maybe that explains why I was able to drive my Corolla with a blown head gasket to work for a few months later down to road. 170miles round trip in 80-100F Florida heat. Just kept adding coolant. I believe the reason may of been using Royal Purple oil in the car and ran it for 10k miles. Don’t use Royal Purple unless you want problems with your engine guys! Oil is complete garbage! Company shouldn’t exist.

 

[A90MT]

Normal operating mode. When at high loads, coolant pump control goes into escalation mode to hit a lower target temp and temps drop, then come back up after you let off.

Oh, that's Interesting. I didn't know that. Thanks for sharing. It still seems odd to me that it's triggered on smaller inclines at 1/4 throttle but I suppose the RPM difference could be considered high load.

I'll have to take a look at the target coolant temp next time, I had no idea that feature existed. Good to know!

 

[rottmore]

When pertaining to the smoke, its probably just the PCV system. Do you have a catch can, or are you routing all the blowby back into the turbo? My smoke reduced after i deleted the PCV. If you want to do a complete delete, you can tap & plug the PCV ports on the head or order some blockoff pins.

When it comes to smelling coolant. I don't know. I've had that happen before, Thought i smelled coolant, freaked out, ordered a block tester just to find out everything was fine. The block test will let you know for sure if there's combustion gases leaking into the coolant.

 

[A90MT]

I always notice that after flooring it.

How low does your coolant temp drop after flooring it ?

When pertaining to the smoke, its probably just the PCV system. Do you have a catch can, or are you routing all the blowby back into the turbo? My smoke reduced after i deleted the PCV. If you want to do a complete delete, you can tap & plug the PCV ports on the head or order some blockoff pins.

When it comes to smelling coolant. I don't know. I've had that happen before, Thought i smelled coolant, freaked out, ordered a block tester just to find out everything was fine. The block test will let you know for sure if there's combustion gases leaking into the coolant.

I don't have a catch can setup. Just running the factory pcv system right now. However, I do plan on doing pcv block off pins when I replace the head gasket since I'll be in there anyways. I can understand small amounts of smoke but it was ALOT. I'm still leaning towards blown head gasket. I just ordered a boroscope to take a look inside after doing the block test.

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