Coolant is dropping in my radiator. There is bubbles of gas coming out the radiator when the car is running. So, this seems like a bad head gasket.

I think my options are to change the head casket or the engine.

However, I'm curious, if I top up the radiator before every drive. What will happen in the long run? Is this dangerous or is it sustainable?

  • I really think this question is highly subjective. You say there is a drop in radiator fluid. How much how often? How long will it last? Depends on the engine involved. Depends on how much its driven. Depends on how hard you beat on it. Depends on a lot of things which you don't answer and cannot really answer. Not closing it outright as an opinion question, but my thinking is leaning that way. Jan 9, 2020 at 2:34
  • I agree it's a bit tenuous but overall think that's an answer @Pᴀᴜʟsᴛᴇʀ2
    – GdD
    Jan 9, 2020 at 8:27
  • 1
    If you're looking at an engine already, or a head gasket, it might be worth trying a bottle of head gasket sealer. I'm normally not a fan, but for $50 it's worth a shot, especially if this is a high mileage car where cost of an engine or head gasket replacement can approach or exceed the value of the car.
    – 3Dave
    Jan 10, 2020 at 18:54

4 Answers 4


The long term effect is that the leak will etch a groove in both your engine block and heads. There may be a groove already there, but it could still be within "surface flatness" standards. Causing structural damage to your block and heads is a costly mistake.

The "flatness" standards for each gasket mounting surface should be outlined in the shop manual for your vehicle.

Example of Block Damage from Blown Head Gasket


It's impossible to say how long a relatively minor head gasket failure will stay that way, it depends on the placement and nature of the failure, as well as other factors. It will certainly get worse, either all at once or gradually. Being gentle on the power will certainly help.

If it's gradual you can live with it, but all the while you're getting oil in your coolant and coolant in your oil which doesn't do either your engine or your cooling system any good. A minor loss of power may become a more serious loss of power and a rough running engine if the gasket is blown between 2 cylinders as the pressure loss leads to poor compression. Bleed-over between cylinders can cause valves to foul up and need reconditioning. Long term it could lead to more expensive problems than a head gasket replacement.

If it gets worse suddenly you could have an engine failure, which could potentially be dangerous or at the very least inconvenient.

  • 1
    a head gasket can fail without oil or water going either way...
    – Solar Mike
    Jan 9, 2020 at 14:03
  • Of course @SolarMike, in this case we know they are.
    – GdD
    Jan 9, 2020 at 14:06
  • Do we? gas is getting into the coolant but no mention of oil in the OP's post.
    – Solar Mike
    Jan 9, 2020 at 14:07
  • Well, I'm making an assumption that if there is pressure from a head gasket and a drop in coolant that there is a transfer at least in one direction. In order to have a rounded answer about the problems leaving a blown head gasket it makes sense to point out the complications.
    – GdD
    Jan 9, 2020 at 14:11
  • Then one you missed is when the head gasket fails between two adjacent cylinders - misfire and loss of power are symptoms but not effects on oil or coolant...
    – Solar Mike
    Jan 9, 2020 at 14:13

Just to illustrate how subjective this question is - about 10 years ago, I bought a 1939 Farmall tractor from the son of the original purchaser. The family had actively used the tractor on a small farm from new until a few years before I bought it, it had unknown thousands of hours on it.

It clearly had a (minor) headgasket leak. The son (who was in his late 60's at the time) told me he'd been topping up the coolant every few weeks since he was a child. The headgasket had been leaking for at least 50 or 60 years when I bought it, yet the tractor ran okay.

Clearly, that motor is significantly different than the one in your vehicle, and I would not advocate for letting a headgasket issue go unfixed for half a century - but, the point remains: it's pretty difficult to guess if or when a headgasket leak will lead to serious issues.

  • A lot of words to say what I put in my answer....
    – Solar Mike
    Jan 9, 2020 at 16:56

It may fail at any time. Some have been known to go on for years, others next day or week.

If you value the vehicle then get it fixed, if not then when it fails dump it.

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