PT Not Cruising
May 18, 2013 10:40 AM   Subscribe

I'm having overheating trouble with a 2001 PT Cruiser recently given to me by my father-in-law.

The car never had trouble on the limited excursions he was taking it on, but ever since I drove it from Wilmington, NC, to Milwaukee, WI last January it's been overheating. The trouble actually started on that drive; the car pooped out in Indiana, and it turned out the coolant reservoir was dry. (Since he'd just flushed and refilled it, our theory is the coolant got too hot and boiled out of the reservoir, which is possible in that build.)

Since then we've flushed the radiator (twice), once with anti-rust additive to try to break up any blockages; replaced the water pump and the water outlet neck; replaced the thermostat and thermostat seal; and a input hose that was found to have a tiny leak. Nonetheless, the car had again already begun to run hot on 80 miles into a 400 mile drive yesterday -- the temperature gauge was three quarters of the way to the red line when we abandoned ship and got a rental. The coolant reservoir was still full, and filled to the fill/HOT line; so it just seems like any prolonged amount of highway driving is too much for the car to take.

The only thing left on the Top Five Reasons Your Car Overheats list is the fan, which they say seems to be working. That's next on the list, I guess -- but if it's not that, any idea what it is?

Thanks so much!
posted by gerryblog to Travel & Transportation (12 answers total)
To clarify about the fan: we've looked at, the mechanics have looked at it, it seems to be working. But perhaps it's only working sporadically, or only when the AC is on (or off), or something like this? Yesterday the car had crept up to 3/4 of the way to red line while highway driving, but when I turned around and drove at a non-highway pace to the nearest car rental place it ticked back down to normal temperature. I'm not sure if I fiddled with the AC during that time.

I hate cars and don't know anything about them, if that isn't obvious.
posted by gerryblog at 10:45 AM on May 18, 2013


Are you bleeding the coolant system as described in the workshop manual?
posted by BenPens at 10:46 AM on May 18, 2013

My father-in-law maintained the car religiously. I've taken it to my local mechanic twice and the dealer once; I haven't touched anything myself.
posted by gerryblog at 10:48 AM on May 18, 2013

Well religious or mechanics, the symptoms you describe are consistent with air in the coolant system. Mention it to the FIL, see what he says. He may not be used to such a procedure.
posted by BenPens at 10:55 AM on May 18, 2013

That's a 12 year old radiator, and likely, a 12 year old radiator pressure cap you're depending upon, to keep things cool in a car with a tight engine compartment, and well known overheating issues. At a minimum, a cooling system pressure test should be done, and if the system can't hold required pressure, the cause (pinhole leak in the radiator, bad pressure cap, etc.) of the leak should be remedied, before you drive the car much more. A pressure test might also reveal excess pressure being developed in the cooling system, which is usually indicative of head gasket failure, allowing hot combustion gases to leak into the cooling system; you might also look for "milky" discoloration in your oil, on the dipstick, indicating coolant is being allowed to pass through to a cylinder, and also for white smoke out the tail pipe shortly after start up, which are also both classic symptoms of head gasket failure.

As to the fan issue, at highway speeds, the fan is usually disengaged electrically, to improve gas mileage, as sufficient air flow through the radiator should be provided by the normal air stream of the car moving down the highway. The fan is mainly turned on electrically as needed in stop and go traffic, or after the car is turned off, to provide cooling air, to keep the car from overheating when natural air flow isn't present.
posted by paulsc at 11:13 AM on May 18, 2013 [2 favorites]

I really doubt the NC to WI drive itself caused the problem; I've taken my own 2003 Cruiser on many longer trips without trouble (unless you count the time I encountered a monster car-eating pothole in Massachusetts, but that's a separate subject!). And I am not nearly a good enough mechanic to diagnose your trouble, but I can personally really, really recommend that BenPens has linked to.

It's free to sign up and ask those folks: they're a really nice community (and like MeFis, they are a community), and there are plenty of Cruiser experts as well as some damn fine shade-tree mechanics there more than willing to help anybody with anything Cruiser-related.
posted by easily confused at 11:15 AM on May 18, 2013

A car should never overheat on the highway. Between the direct air cooling of the motor, and the air rushing through the radiator, and the relatively low load that's on the engine, it should never happen. As paulsc says, the fan should not be running while at highway speeds.

Even if there is air in the system, it should work its way out eventually. Even if it doesn't, the reduced cooling it causes will not slowly increase over a long trip.

What is probably for sure happening is that you have a bad head gasket. Here's what happens normally: the car runs, the coolant heats up and pressurizes the system, the thermostat opens and water flows through the radiator. Any air in the system turns into tiny bubbles, as well as any coolant that boils slightly. If the system over-pressurizes for some reason, the radiator cap lets the coolant burp into the overflow tank. Then, as the car cools off at night, a slight vacuum occurs in the system and the radiator cap opens in a way that allows coolant from the overflow bottle to suck back into the system.

So, the first thing is to make sure all the tubes are correctly hooked up for this. If the tube that comes off the radiator cap mount area isn't connected and plumbed to the overflow bottle, and the bottle isn't plumbed correctly (either a dip tube or a siphon of some kind), this system won't work and you'll get air in the system.

But even then, you'll have reduced cooling capacity, but you won't have it continually increasing over the course of a roadtrip.

Unfortunately, given that's you've done all the easy stuff, one has to start thinking that it is a bad head gasket. What happens in this failure mode is that the gasket fails between the combustion chamber and the coolant paths, and every time that cylinder fires, a small amount of pressure is let into the cooling system. Over the course of a long trip, this pressure displaces more and more of the water in the system until there isn't enough water to keep the car cool. (Which makes it overheat, which makes the break in the gasket worse.)

The good news is that a head gasket replacement on an inline 4 cylinder engine isn't all that bad, and given that you have a car that's been meticulously maintained, I would expect that the job will be worth it.
posted by gjc at 1:45 PM on May 18, 2013 [1 favorite]

You might be interested in this conversation. It could be time for a new radiator...maybe.

Also, do you know the temperature rating of the new thermostat and what 3/4 to the red line means in degrees? My truck has too thermostats. One puts it on the first "E" in Temperature. The other on the second "T". Ford seems to think both are OK. I went with the former.

If you went for a drive with an OBDII reader with a diagnostic mode it should give you the exact coolant temperature plus about 400 other fun pieces of engine data.
posted by Kid Charlemagne at 7:25 PM on May 18, 2013

When my car was overheating even though the fluid was full, it was the head gasket.
posted by MexicanYenta at 10:31 PM on May 18, 2013

Since he'd just flushed and refilled it, our theory is the coolant got too hot and boiled out of the reservoir, which is possible in that build.

Not really. Coolant only gets too hot if there is something wrong - all designed cooling systems are bigger than they need to be so they have the capacity to cope with the hottest days. If it was january in Indiana, that was surely not the case so there should have been no issue.

Its ounds like he didn't bleed the system properly. It also sounds like the head gasket was damaged during this overheating period and now the problem is permanent (and internal engine rather than an ancillary part). I'd be pretty surprised if this wasn't a head gasket and I think the cooling system problems you have now are a result of the problem, rather than the problem itself. Stop spending money on the cooling system and look at the heat source (Ie the engine).

The only thing left on the Top Five Reasons Your Car Overheats list is the fan, which they say seems to be working.

Fans are purely there to replicate the air through the rad when driving. They only really stop the car overheating when you're sitting in traffic or driving very slowly and unless the car was always fine at speed but overheated in traffic, it isn't the fan. LIke I say, the cooling issues are the result, not the cause.
posted by Brockles at 8:24 AM on May 19, 2013

There's one other simple test that might confirm a blown head gasket, and that is a comparative compression test. For that test, a mechanic removes the spark plugs from each cylinder, and uses a pressure gauge stuck into the spark plug hole of each cylinder, one by one, to measure the maximum gas pressure each cylinder can produce when the engine is briefly turned over with the starter motor. In a good engine, all the cylinders will be able to produce pressures within 10% (+/- 5%) of one another, and within perhaps 15% of new engine specification. An engine with a bad head gasket will have low pressures on one or more cylinders.

A cooling system pressure check, and a compression test, together, shouldn't take more than an hour or two of diagnostic time. You will have to leave the car all day, or perhaps overnight, as the cooling system check needs to be done with the engine starting from a cold (ambient) temperature state. But a good mechanic, armed with the results of these two tests, should be able to accurately diagnose the car, and give you a repair estimate. And you should get some test results that independently confirm the diagnoses, which may alleviate any feeling that your lack of knowledge is being used against you, to sell you unneeded work.

If you do decide to fix the car, and it does turnout to be a head gasket, you might also want to have a valve job done, while the cylinder head is off, and have the head checked and or minimally milled for true dimension. No point in putting back a warped or cracked head with leaky/worn valves. And of course, you get new exhaust manifold gasket, new intake manifold gasket, and such other seals and gaskets needed in the rebuild. So an engine with this level of repair is referred to as having a "top end" rebuild. If you're keeping the car, you probably do want to replace the radiator, too.

Altogether, I'd expect basic repairs to come in around $2000 to $2500, perhaps $3000 if you have a valve job and replace the radiator, which is a substantial portion of the value of the car. Normally in these cases, I might suggest that you look for a used engine from a junkyard, to save some money, but this model car had a reputation for engine overheating, so any used engine you get might well be a short time fix, too. Still, if you just want to fix it and sell it, a lot of junk yards will give you a 90 day exchange warranty on used engines, which would get the car off your hands in working condition.
posted by paulsc at 2:47 PM on May 19, 2013

new radiator, I don't know about that car but 2 rangers w/ aluminum radiators, same symptoms....
posted by raildr at 6:46 PM on May 19, 2013

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