2013 Prius, 170k miles. I started doing maintenance on my own after getting into all the various channels on YouTube with repair content. Next week I'm planning on cleaning the EGR and intake manifold along with installing new spark plugs and valve/tube gaskets. I've noticed that every once in awhile, especially when it's cold, my car will start up rough for about 5-10 seconds and then run normally. From what I can tell, this seems to be a very early symptom of a head gasket leak. I know there have been numerous threads about this; however, I haven't really seen it discussed as far as whether or not you should have the head gasket replaced preemptively (at the very onset of these issues). Everyone seems to say that you should wait until there are more advanced symptoms or the car stops running... which all seems counterintuitive to me as that can cause permanent engine damage. I would be doing this repair on my own so I'm not worried about the cost of parts or the time it takes. I do wish there was a step by step replacement tutorial available somewhere (like "NutzAboutBolts"); however, I feel like I have a fairly good understanding of what's involved after having read through the service manual and watched multiple at length videos of people replacing head gaskets on other vehicles (as well as that 2 hour long video posted by "Gasket Masters"...albeit without commentary). Any thoughts or suggestions would be most appreciated!
The reasons why most people lean away from preemptive HG replacement is that the shop labor is expensive and/or the time and effort involved makes for a tough weekend project. In your case it might rather be like open heart surgery for a patient that shows no signs of cardiovascular disease. You will know more once you've done the angioplasty on your EGR circuit.....
I was thinking leak down test to see if head gasket is leaking before replacing it but replies will say yes replace it.
Why not. I had a Toyota T100 truck that Toyota recalled for head gasket replacement. There were no signs of failure on the engine but they did the replacement anyway. I suppose, because of a recall, they had to; but if they operate that way then it should tell you something.
Thanks for the replies everyone. Just curious, anyone have stats on how long the timing chain lasts? Not 100% sure. I changed the coolant about 2 weeks ago and haven't noticed a drop yet. However, before I changed it the level had dropped below the minimum level... however, I hadn't changed it in a few years so I can't say if the drop was due to a small head gasket leak or just regular use. To be honest, in the past I wasn't really paying attention to these things as well as I should have been.
The cooling system is a closed system. When functioning properly it should consume zero coolant. Unlike engine oil -- in which consuming a small amount would be considered normal. I would suggest filling the cooling system to the FULL mark and watching it diligently. In order for your measurement over days and weeks to be accurate, you need to observe the level under repeatable circumstances. Best case scenario would be to fill it, drive the car for a while so it gets up to full operating temperature, then park it for the night. The next morning check the coolant level. Then continue checking each morning for the next couple of weeks. If you want, using your phone take a pic each day with the phone in exactly the same spot/position. If you have a borescope or endoscope ($15 on Amazon, works with your phone) you could pull the plugs a few mornings and look inside the cylinders to see if anything has accumulated. I'd be hesitant to do a head gasket as a preventive measure. But that's just me.
If you want to avoid buying a gallon of the coolant, and assuming the coolant’s not really low: park the car in usual spot (hopefully level), and when totally cooled down, put a strip of masking tape on the reservoir sidewall and mark the current level with a sharpie. Then monitor for a while. One issue, the reservoir has that big horizontal seam, just below the full line, but anyway just go up and over it I guess. I’d second leak-down test mentioned by @Grit, btw. That’s the definitive way to test.
