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Was wondering if it is safe to use seafoam through my brake booster vacumm line? If I drip it in SLOW can I still hydrolock my engine?

It is safe if you drip it in slow enough. And if you did it too fast, the engine would probably just stall due to rich mixture ratio rather than hydrolock, though I wouldn’t want to test that theory in the extreme.

But many people have successfully used the brake booster vacuum line. Using a funnel jammed into the hose and dripping the seafoam slowly into the funnel helps control the flow rate, rather than sticking the hose straight into the bottle.

Why would you use the largest diameter, highest Airflow volume vacuum line you have to try and add a liquid as “slowly” as possible…would be my first question.

It can be done sure…but you need to know what you are doing. An aquarium airflow valve, a pickle jar, some tubing…and the Venturi effect will work nicely…but If you are not a Professional…I would suggest a much smaller vac line…

I promise you wouldn’t be very happy if things went wrong w the brake booster line method…and it would take a literal moment to have an extremely expensive “whoopsie” event…One which your wallet and your Ego would enjoy none too much.


I agree with Honda Blackbird. That large line is going to cause problems trying to keep the engine running because once disconnected it will be the largest vacuum leak possible.
A little slip on a line that large and as Honda Blackbird mentions and you could be facing expensive problems.

If you must use SeaFoam then dribble it in slowly until the engine stumbles. Allow it to even out and repeat. Note that soon after the exhaust will smoke horribly. This is normal and it will pass.

I would pick a small line (say the fuel pressure regulator or whatever) and tie into that.

Here’s how I decarbonize engines using SeaFoam

Remove the brake booster vacuum hose from brake booster check valve.

Take a smaller diameter hose and insert it into the brake booster hose.

Take the smaller hose and put the end into the can of SeaFoam.

Take a pair of pliers and pinch off the this smaller hose.

Have someone start the hot engine and bring the idle speed to 2,000 RPM’s.

Slowly open the pliers so the SeaFoam begins be drawn into the engine. It’s here where you want to open and close pliers to meter the amount of SeaFoam entering the engine, and where the throttle is manipulated to prevent the engine from stalling.

Once all the SeaFoam has been drawn into the engine shut the engine off.

Reconnect the brake booster hose.

After a half hour has past, restart the engine and bring the idle speed back up to 2,000 RPM’s until the smoke clears from the exhaust.


Are we trying to fix a problem that does not exist. It would be nice to know what the actual problem is.

OK first I was told the brake booster line will evenly distribute seafoam to all cylinders. I like the method of putting a smaller hose into booster line. I have a syringe like thing (I think its for cooking not the needle one) that I will use to add seafoam…wich will allow me to slowly add it in drop by drop. Does that sound like s good idea? And no I’m not trying to fix a problem that doesn’t exist my car is at 209k miles and has used 87 octane most of its life. My throttle body and pistons has a lot of carbon build up.

If you want to clean both the throttle body and intake valves, here’s the SeaFoam product you want to use.

Instead of introducing the SeaFoam via the brake booster hose, it’s introduced up-stream of the throttle body. So the throttle body, intake plenum, and intake valves are cleaned.

With the mileage on your engine, it may take more one than treatment to be effective.

NO! I’m not a rep for Seafoam. But I’ve used it for over forty years. And it works!


What you were told about the brake booster line evenly distributing SeaFoam to all cylinders is not entirely correct.
Yes, that part is true.
What is also true is that any vacuum line from the intake manifold system, larger or tiny, will evenly distribute the SF to all cylinders.

When I use it on my cars I generally feed it through a PCV hose in the intake tract above the throttle plate and after the MAF sensor. This also feeds it to all cylinders.

"And no I’m not trying to fix a problem that doesn’t exist my car is at 209k miles and has used 87 octane most of its life. My throttle body and pistons has a lot of carbon build up."

"Are we trying to fix a problem that does not exist. [?] It would be nice to know what the actual problem is."

Chrysler 209k miles
Make? Model ?
No problems?

I have cars with 100k to 300k. If they have carbon in the throttle body and on the pistons it hasn’t changed anything, as far as starting, running smoothly, or still getting the MPG they’ve always had. My 2001 3.8L Impala LS still starts instantly, runs very smoothly and delivers 30MPG.

Perhaps you’ve done some research and I’m curious to know how you know you have problematic carbon build-up if there are no symptoms? Why not leave it in place and maybe just wax the car or vacuum the interior, instead?

On my Camry with 150 K miles, when i had to change my Battery, I noticed the car was idling funny and almost stalled. It was carbon build up in the throttle body and the ECU had adjusted to it and now was reset because the battery was off for 10 minutes (me waiting in the Costco line!).

At any rate, some manual cleaning of the throttle body took care of it.

Car is a 2006 Sebring 2.4l dohc. 4 banger

Problems currently having are power loss, engine sounds loud lightweight like a diesel engine, Carbon build up, and every now and again it catches a cold.

My main concern is restoring power. Might be fuel, might be compression idk but I would like to see if seafoam will restore power as it claims since its only $7 a can, heck why not.

Does the can say you can put it in the gas tank? If so, it will all eventually go to the same place as the brake vacuum line method, so that might be the easier way as a first try. You might get lucky. My guess though is that if carbon build up is actually causing the reduced power symptom, Tester’s method would work better than adding it to the fuel tank.

If your engine sounds like a Diesel…and that is an accurate description… Seafoam isn’t going to help you.

I agree with Honda Blackbird.

SeaFoam is a great product but it’s also not a miracle in a can.

I assume by loud engine you mean the engine is rattling? If so, is it rattling at idle or only on acceleration?

I agree with others. You first need a diagnosis of the engine problem, then you will have the fix.