Head Gasket Replacement Resources for Newbie

Research how to perform a leakdown test. Besides needing a leakdown gauge set and air compressor, you have to get the piston to Top Dead Center on the compression stroke -within a couple degrees so the piston won't just spin the crankshaft when you pressurize things. Remove the radiator cap in case it is a bad H/G leak.

Pretty much the only way for a head gasket fault to reduce compression that much would be a (large) breach between the coolant passages and the combustion chamber. You would have coolant loss, overheating, white smoke out the tailpipe, coolant being pushed out of the radiator cap and overflow tank, and - misfire.

Low compression could be: damage to a valve or piston (or H/G,- any of them not sealing), bent connecting rod, (or a valve timing problem or air restriction- very unlikely to affect just one cylinder). Gonna have to diagnose this before tearing things apart. Good idea to get a copy of the factory service manual.

That said, unless you don't really need that car, trying to do that level of engine repair without a fair amount of automotive experience is....VERY ambitious. It can be done, but you need space, tools, time (-lots), information, and a tolerance for risk and failure.

Learning anything new involves making mistakes. If your "first" engine repair is a major job then be prepared for the possibility of major failure. (hope for the best but plan for the worst).


Posted via the PriusChat mobile app.

 

I've never done a leakdown test without making sure the crankshaft can't turn. I generally put a breaker bar and socket on the pulley nut. I have sometimes had the breaker bar sticking up, and lashed it to the engine mount, or sometimes down with its end against the ground and my foot behind it. It's usually not hard to immobilize one way or another.

My leakdown tester's instructions are to secure the crank against turning, and to me that makes sense. Trying to locate top dead center (what math geeks would call an "unstable equilibrium") so precisely that it won't spin under 90 or 100 psi pressure sounds like it might be a fun test of skill once or twice, but too fussy for the day-to-day.

 

Get a Block Tester from Amazon for around $30. It will test the coolant for exhaust gasses. If it tests positive you have either a blown head gasket or a cracked head. Almost always, if it tests positive, it's a head gasket problem and is rarely a cracked head on a Gen 2. You will have your answer in a few minutes and for very little cost or effort. It's very easy to do.

It is possible to have a head gasket blow just between cylinders and not involve the coolant at all, but that would be rare. If your car does fail this test it's pretty definitive.

Good luck

 

Unless you see white smoke or water in the oil I am thinking it isn't a headgasket at all. I just went through this myself and I think most of the headgasket problems are on Gen3, or just really abused Gen2s. Don't get me wrong, I abused my Gen2, but mostly due to oil consumption and not overheating. See the video I posted in my thread here, if your car sounds like this then it is probably just fuel injectors. I bought 4 reconditioned injectors from eBay for about $40-50 and out them in myself and it is a new car, no engine lights, no death rattle. Fuel system cleaners don't work for bad injectors, and bad injectors can be intermittent like mine were, mostly at idle for me. 2008 2Gen w 190k - Misfire 300, 301, 303 | PriusChat

 

Low compression like yours is not an injector, spark plug, coil or head gasket. More likely mechanical damage where replacing the engine would make more sense. The advice you received from local shops was good.

People have a tendency to spend a considerable amount of time and money on the "easy" stuff which turns out to be a waste. That is known as "shotgunning" or firing the "parts cannon" on the job, often over a period of weeks.

If you actually bought a new hybrid battery, as opposed to a "rebuilt", then fixing the engine in this market makes reasonable sense. A new battery would have been at least $2,000 installed. A good shop could swap the engine in two days, give you a warranty and you move on with your life.

 

This is really not true at all. Watch this YT vid. This guy is a Toyota Master Tech and his vid is pretty informative.

How to Check for a Bad Head Gasket on Toyota and Lexus Engines - YouTube

 

Thank you for the link. Well it is true for an actual blown gasket, that video shows a "bad" gasket which is not blown. It is a great video, but he is loading up the cooling system with more pressure than it can hold since the stock radiator cap only about holds back about 12.75 lbs. Also he is doing it cold before the block and head have expanded with heat and likely seal that up. From my understanding the main problem with these engines is that the head bolts are steel which don't expand the same as aluminum and the aluminum head and block if heated too much expand against each other and crush the head gasket. I would definitely drive on what he is showing in that video and likely not get any codes or rattles, but I do agree that the problem won't get better and will continue to progress. In my experience it takes more water than moisture, or a drop, to hydro-lock an engine or be considered a blown gasket. According to the video too, if my 2008 sweated coolant like that in a cylinder it could cause more damage trying to fix it than just leave it as is.

 

OK.
If I interpret what you're saying correctly, he did it wrong so proving the coolant has been contaminated by exhaust gasses has no meaning and you would drive a vehicle with a blown head gasket. OK then.

Cheers

 

The fact that your seeing this at that mileage means the engine was probably not cared for well so makes it not worthwhile for a head gasket. Blown head gasket is not common for this motor. Gen 3 for sure but not this engine.

The fact that your wrenching experience is mainly on bikes does not bode well For this fairly complicated job. It’s a lot of work and requires precision re-assembly.
Don’t think theres any G2 head gaskets on YouTube. But I just looked at a G3 head gasket job on YouTube. Fairly involved.

I woukd just replace the engine with a used engine. Lots of used G2 engines out of wrecked cars with lower mileage. There’s many g2 replacement posts.

 

My apologies I missed his results from the combustion gas test, it is a great video. My main point is not to assume a rough idle is a bad or blown head gasket, especially if problem is intermittent. I just went through repairing a misfire on 1 and 3 myself and it was injectors, and most posts here had me worried about possible head gasket, rod knock, worn rings, and worst case scenarios. I could have exhaust gases in my coolant too, I will probably check, but refurb injectors solved my misfire that several mechanics didn't fix and I'm back to 43+ mpg with new oil and coolant. I don't hear any gurgling and don't see an obvious consumption of coolant, but I could still be seeping some into a cylinder under certain conditions, and allowing combustion gas into the coolant. So I am running in the "if it isn't broken, don't fix it" stage with the head gasket.

 

The OP's real issue is bad compression in one cylinder 80 psi versus 120 psi.

 

Eh, do enough leak down tests and you get the hang of it. Put a long screwdriver down the plug hole on top of the piston. Breaker bar on the crank pulley bolt. Once you're near TDC on compression, keep going until you see the screwdriver JUST start to drop. Make a "note" of where the breaker bar position is. Now go backwards until the screwdriver goes up then JUST starts to drop again. Split the difference on the breaker bar position from before. Then start the test at 50psi.

Posted via the PriusChat mobile app.

 

"Just" replacing the engine (with a good one) certainly would take care of your compression problem. However, if you've got the time and the attitude, then there's no reason not to try and diagnose this. Maybe you could fix it- or not. Whatever happens you'll learn something.

Posted via the PriusChat mobile app.

 

I have a 2014 standard Prius with 185,000 miles. We got, well actually our daughter got, 340,000 miles on our 2007 before the batteries gave out for the second time. In July we attended our grandson's wedding in Birmingham in the 2014 Prius and on the way home the upper return hose to the expansion tank popped off. Unfortunately the temperature sensor was defective and no lights came on on the panel. As we went up a mountain near Gadsden I heard a noise and lifted off the gas and heard a loud rattling noise. I immediately pulled off and stopped the engine. It was very hot. I waited ten minutes and attempted a restart and the engine death rattle occurred. We ultimately towed the car home (after an exciting 4th of July weekend at the Gadsden off ramp) and the dealer told us the engine was destroyed. I ordered a JDM Japanese imported used engine, took out the old engine, (thanks Youtube) and installed the new engine. Unfortunately the replacement engine was worse then the original. After getting my money back and taking out the replacement engine, I decided to rebuild the old engine. It has proven to be a daunting task, but I learned several things. First the 1800 is a complex engine with a block that dis-assembles into four large pieces, and 35! sensor and wiring connections. The old piston rings had an end gap of 00035. The new Toyota ring end gap was 00065. So the old rings have tighter clearance than the new ones (but are much thicker). Finally after I put it all back together it ran fine, but overheated. (The new temperature sensor actually sets off the dash warning light) I checked the water pump and it was running fine. I feared the dreaded head gasket failure due to improperly installing it. Then my car mechanic informed me that failure of Prius water pump impellers is well documented in the repair websites. So I took the water pump off; hooked the connection back up and his computer was able to turn on the pump. It ran fine, but the impeller didn't turn. On taking it apart I discovered the impeller had melted from the heat of the engine overheating, and was completely disconnected from the motor shaft. So after a long story, the moral of this saga is, if your Prius blows a head gasket (which is how most of them die) always replace the water pump, or you'll blow it again.

 

Loose consensus here is replace the water pump (aka engine coolant pump) around 120K~150K miles, just treat it like a maintenance item. Maybe similar for the inverter coolant pump?

Had the EGR components (and EGR passages on the intake manifold) ever been cleaned on the 2014 3rd gen with 185K miles?

 

Gen2 1.5L engines rarely have head gasket issues. Some burn oil. Lost compression is not a good sign. A borescope inspection or leakdown test might determine if it is a bent rod or damaged valve.

Since a simple head gasket is not going to cause a 40 psi compression drop its either engine out for a rebuild or for a replacement. Lower cost for a used replacement usually makes it the choice but a rebuild is a longer term better fix. A replacement is much easier than a rebuild.

 

How confident are you in your compression test results? It sounds like you did it correctly, but I know my screw-in compression tester is old and I might need a new one or new seals. It could be worth paying for a diagnostic, compression and leak down test.