Cylinder Head Questions

[microfiz]

Hi, I have a 2006 PT Cruiser (2.4 L NA DOHC).

It has overheating issues. It was my daughter's car while she was in college. A month ago, I decided to drive it back home so I can tear into it finally. The drive was about 450 miles. During the entire trip, I was monitoring the coolant temperature using the OBD read-outs (through WIFI and phone). With the outside temperatures about 60 deg F, the coolant temp averaged 190 deg F for at least 300 miles... keep in mind that I kept the rpms at around 2500 (definitely under 3K). However, I had to overtake a car and stomped on the throttle a bit to the point that it downshifted and probably shot past 4000 rpms. That's when I noticed that the coolant temp creep up fairly rapidly. I pulled over before it reached 240 deg F... it was boiling over at that point.

After it cooled, I filled it back up with water and drove the remaining 200 miles uneventfully (again, under 3K rpm and coolant temps registering in the 190 deg F range). When I got home, very little water was lost.

I have a very strong suspicion that it's my cylinder head (or gasket). I'm actually in the process of removing it now (have not removed the timing belt yet). Am I right in my hunch?

I also want to know if I can do the cylinder head removal WITHOUT removing the AC line. Can anyone answer this question? Thanks.

[Handy_Cruiser]

As a general rule, when a car begins to overheat at higher speeds (higher RPM's) on the highway but runs cool at lower RPMs, you need to look at the radiator. A stopped up radiator will do this very thing. And it's often the opposite of symptoms you see with other cooling problems. I think this is even a question on one of the the ASE automotive tests.

In many cases, a blown head gasket is going to start leaking compression into the cooling system by the time or after the engine reaches operating temperature. So symptoms often occur even at lower cruising RPM's. Doing a chemical test for combustion gas in the radiator is likely the best way to check of a very mildly leaking head gasket. And it still might be worth it before changing out the radiator.

If me, I would first remove the thermostat and flush the cooling system very thoroughly. Then I'd put in a new thermostat, refill with water, and make sure I bled out all the air using the bleeder valve below the thermostat housing. Then I'd see if I got the same symptoms. If I did, I'd spend a little time driving in the 2,500 and lower RPM range just to make sure I'm right about it doing okay at that range. If all the symptoms stay the same, I'd likely replace the radiator.

Remember that it's always possible to have a failed head gasket that was caused by another heating problem that happened first. So I can't say for sure yours is okay. But this would be my course of action on my PT.

It should be noted that I am a Safety Engineer among other things and I haven't worked as a professional mechanic since I was young strapping lad with long sexy flowing hair before college. And even then, I mainly worked on big trucks and heavy equipment. Nowadays, I enjoy working on these funny looking little cars for fun and relaxation.

[microfiz]

Thanks, Handy Cruiser! I failed to mention that the following things have been replaced: Radiator, thermostat, cooling fan, radiator cap. My wonderful daughter did manage to overheat it to the point of engine shutdown at least once prior to my 450 mile drive. The lost coolant spews out from the overflow reservoir.

Since I am replacing the timing belt, along with the fact that the car overheats and PT Cruisers are notorious for cylinder head/gasket issues compels me to pull out the head. Do you know if I need to remove the AC lines for this endeavor?

[ptcruisersteve]

Originally Posted by microfiz

Thanks, Handy Cruiser! I failed to mention that the following things have been replaced: Radiator, thermostat, cooling fan, radiator cap. My wonderful daughter did manage to overheat it to the point of engine shutdown at least once prior to my 450 mile drive. The lost coolant spews out from the overflow reservoir.

Since I am replacing the timing belt, along with the fact that the car overheats and PT Cruisers are notorious for cylinder head/gasket issues compels me to pull out the head. Do you know if I need to remove the AC lines for this endeavor?

I would recommend that you check the engine compression for all 4 cylinders before pulling the head. You want to make sure you are covering all issues that might come up.

[Handy_Cruiser]

Originally Posted by microfiz

Thanks, Handy Cruiser! I failed to mention that the following things have been replaced: Radiator, thermostat, cooling fan, radiator cap. My wonderful daughter did manage to overheat it to the point of engine shutdown at least once prior to my 450 mile drive. The lost coolant spews out from the overflow reservoir.

Since I am replacing the timing belt, along with the fact that the car overheats and PT Cruisers are notorious for cylinder head/gasket issues compels me to pull out the head. Do you know if I need to remove the AC lines for this endeavor?

You are right. I'd be thinking a head gasket too based on what you said.

A compression test may or may not tell the story. On some really small head gasket leaks, I've had several cases where neither a compression test nor a cooling system pressure test showed anything. But if you have a compression tester, it might be worth it. If not, I'd do a chemical test since it will be the most definitive. Either way, as mentioned, I'd try to confirm the head gasket failure before I start pulling the head. And doing the compression test can give you an idea of the condition of the head itself. For me, I always have the head rebuilt when doing a head gasket job. It's money well spent.

And yes, you can remove the head without discharging the AC system. The hoses are not really in the way. I figure the service manual says to do this because it's a little safer for both the technician and the environment since it eliminates the chance of the rupture and release to the environment. But after pulling the timing belt and camshafts a couple of times on my GT, I believe the risk is pretty low.

[PeWi]

the ac lines don't need to be removed and are fairly durable as I had to "persuade" then a few times changing out the head in my 2.4 turbo .... to my amazement the a/c still works in my car

[Wolfman01]

My roommates and I did a water pump and timing belt replacement without removing the cooling lines. Just be mindful of what you're doing when working around them and take time to see how any parts that need to be navigated around them need to be turned and twisted to get around them.

[microfiz]

Thank you for the feedback, guys! I've actually partially disassembled the top end (meaning everything up to and including the valve cover has been removed). Your confirmation that the AC line does not need to be disconnected helps a lot.

[NitroPT]

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[NitroPT]

Mykee can you please provide?post this member with the info of the library to obtain a FSM.