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Overheating and Diagnosis 101 – Non-Turbo PT Cruiser

 
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Old 02 Aug 2016, 03:02 pm
Young Cruiser
 
Join Date: Mar 2015
Location: Liberty MO
Posts: 91
Default Overheating and Diagnosis 101 – Non-Turbo PT Cruiser

I have seen an abundance of posts regarding PTs overheating and a myriad of advice on how to diagnose, then repair. It seems that one single post should be able to answer most diagnostic questions (AND might be pinned for easy referral to forum members).

I’ll take a stab at the common issues:


#1 Failed Radiator Fan

Yes this is quite possibly the Achilles heel of PTdom. Fans often fail and their failure is not realized until the temperature needle hits the peg. Causes are generally (high-speed) motor windings, relay or wiring connection. Diagnosis is straight forward:

1. Check he fan’s motor operation (both speeds) with jumpers. Lots of posts with instructions, but it’s no more complicated than applying 12v to the windings via the connector and seeing what happens. Replace fan if either speed is inoperable. If windings are fine:
2. Check the main harness plug below the radiator for evidence of burn. If burnt, clean or repair as necessary to restore connectivity. If fine:
3. Swap around the relays. On earlier cars, simply move one known good relay to the fan high or low position in the power distribution center (earlier models) or swap relays mounted on the fan shroud (later models).

It is likely that one of the above checks will quickly identify what failed and put you on a corrective path. (If not, you have a one-off failure (ECU?) and may need the help of a dealer.)


Okay, so the fan is working properly, but it still overheats. Here’s where the advice is all over the map, and often contradictory. The first question must be “Under what conditions doe it overheat?” (I assume that most overheating conditions negatively affect coolant level in the radiator. For this reason, I’ll also assume that coolant levels have been topped off prior to any diagnostic.)


#2 Coolant Leak

If there is a wet spot on the garage floor or coolant present in the passenger footwell, you have a leak. A pressure test kit will help you isolate the source without burning yourself (in most cases). Replace the failed component (or components).

NOTE: To be clear, coolant boiling out of the overflow tank IS NOT a leak; it’s normal for an overheating vehicle to boil over/out wherever the system provides for such.


#3 Clogged System

If a PT overheats at idle – temp simply climbs from zero to overheat while idling – something is blocking the coolant flow or there is a leak in the system. Possibilities include:
- Stuck thermostat. This does happen but not as often as people might think. Replacing the thermostat is the old-school replacing things until something works approach. Before replacing the thermostat check the upper radiator hose. If the thermostat does not open (i.e. typical problematic stuck position), coolant does not flow through the upper hose, and it remains cool. If your car suffers from a cool hose, by all means consider replacing the thermostat.
- Blocked radiator. Radiator can become clogged for a number of reasons but flow checking is very easy while still on the car.
1. Disconnect upper and lower radiator hoses.
2. Shove the male end of a garden hose tightly into the upper hose port.
3. Turn on the water.
a. If the hose keep popping out of the upper port (i.e. lots of backpressure), the radiator may be at least partially blocked and need replaced.
b. If water flows freely, assume (for the moment) radiator is fine.


#4 Something Worse (but just as likely if the engine has been repeatedly overheated)

If PT overheats at speed, possibilities include:
- Partially blocked radiator. If there is any question, hold the thought and eliminate the next possibility before replacing the radiator. It may be the cause, but don’t spend that coin just yet.
- Leaking head gasket. Once a PT has been (severely) overheated, it is likely that the head gasket is failing BECAUSE the aluminum head is now warped and requires (as a minimum) resurfaced. (Sadly, many a PT has found its way to the recycler because owners are scared at the cost of this repair. Even more sadly, they further damage their cars by dumping all sorts of canned remedies into the radiator, believing that product X will actually seal a leaky head gasket.)
• Before going any farther, it might be useful to describe the symptoms of a failed head gasket on a PT because this is where much confusion exists.
1. A failed head gasket rarely manifests itself as ‘milky’ oil or exhaust steam. Both symptoms only manifest when coolant (@16psi) is escaping the water jacket into the cylinder (uncombusted at @160-170psi) or oil passages (@0psi).
2. The symptom common to PTs is cylinder gas pushing past the head gasket into the water jacket. It blows (very) hot gas into a liquid, cooking the liquid and bubbling out through the coolant overflow.
• Testing for such a leak cannot be done with the previously mentioned pressure test kit because that kit cannot duplicate the types of pressures causing the leak (>160psi uncombusted) nor the direction of leak flow (i.e. cylinder to water jacket). Testing is most reliably done with a combustion leak test kit (e.g. Lisle 75500 Combustion Leak Detector available from Amazon.com for <$60). Follow the directions with the kit, looking for the blue fluid to turn yellow if a leak is detected. If the PT tests positive, the head must be pulled and redecked, as a minimum.


#5 Something Else?

• But what if my PT overheats at slow speeds but is fine at highway speed? Low speed overheating is almost always a blockage issue. See ‘overheats at idle’ above.

• But my PT always overheats. What about me? Start with the ‘overheats at idle’ scenario and work from there. You’ve got to be sure the basics are working first, and if the cooling fan is not doing its job, nothing else really matters.

Hope this helps.
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Old 02 Aug 2016, 03:11 pm
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Join Date: Aug 2016
Posts: 6
Default Re: Overheating and Diagnosis 101 – Non-Turbo PT Cruiser

I have an 01 and had an over heating issue that was properly fixed. Fast forward 5 weeks to now and my coolant is crap brown and there is a sludge on the sides of my coolant reservoir and no coolant - my car is currently back at the mechanic but I would like your thoughts. Everything I have read has lead me to believe that my cooling system was not properly flushed before being refilled and that it was refilled with standard green coolant (I know that is what it was refilled with)...
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Old 02 Aug 2016, 03:15 pm
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Join Date: Aug 2014
Location: Thousand Oaks, CA
Posts: 7,298
Default Re: Overheating and Diagnosis 101 – Non-Turbo PT Cruiser

Quote:
Originally Posted by deedra View Post
I have an 01 and had an over heating issue that was properly fixed. Fast forward 5 weeks to now and my coolant is crap brown and there is a sludge on the sides of my coolant reservoir and no coolant - my car is currently back at the mechanic but I would like your thoughts. Everything I have read has lead me to believe that my cooling system was not properly flushed before being refilled and that it was refilled with standard green coolant (I know that is what it was refilled with)...
Sounds like you now have two problems. First is you still have a coolant leak somewhere. Second is that the sludge needs to be flushed out asap or it will start to clog up your radiator, etc.

I would suggest a coolant pressure test to see where the coolant is leaking.
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Old 02 Aug 2016, 03:58 pm
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Default Re: Overheating and Diagnosis 101 – Non-Turbo PT Cruiser

That is another thing - checking my garage floor like a crazy person over and over has yielded no coolant on the floor. The last time I drove my car was last week, the day after the check engine light came on. From the time that light came on til it was parked and not driven I drove a total of 16 miles. After the prior issues I wasn't taking any chances. I can tell you that it smelled like burnt krispy (if that makes sense) I also had it towed back to the mechanic bc I was not about to cause more damage not knowing what the problem is.
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Old 02 Aug 2016, 04:03 pm
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Join Date: Aug 2016
Posts: 6
Default Re: Overheating and Diagnosis 101 – Non-Turbo PT Cruiser

I should add that when the initial overheating problem happened that my car was only overheating when the A/C was on high. I had a new radiator installed bc my old one was over 80% clogged but the real problem was my high cooling fan was not working. Installed new fan and relays, new thermostat, system flushed and new coolant, and a new radiator cap. Worked perfectly until the 22nd of July when I drove out of town. Going 80 on the interstate and my temp rose very slightly so I turned on heat through defroster and it immediately came down. I left the heat on until I got off the interstate just to be safe and then rolled windows up and turned AC on and no problems the rest of my trip. That was until the 28th when the check engine light came on and upon my investigation found the brown coolant, very tiny flecks of silver, and the sludgy, empty reservoir.
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Old 02 Aug 2016, 04:33 pm
Obsessed Cruiser
 
Join Date: Aug 2014
Location: Thousand Oaks, CA
Posts: 7,298
Default Re: Overheating and Diagnosis 101 – Non-Turbo PT Cruiser

Quote:
Originally Posted by deedra View Post
I should add that when the initial overheating problem happened that my car was only overheating when the A/C was on high. I had a new radiator installed bc my old one was over 80% clogged but the real problem was my high cooling fan was not working. Installed new fan and relays, new thermostat, system flushed and new coolant, and a new radiator cap. Worked perfectly until the 22nd of July when I drove out of town. Going 80 on the interstate and my temp rose very slightly so I turned on heat through defroster and it immediately came down. I left the heat on until I got off the interstate just to be safe and then rolled windows up and turned AC on and no problems the rest of my trip. That was until the 28th when the check engine light came on and upon my investigation found the brown coolant, very tiny flecks of silver, and the sludgy, empty reservoir.
This is why I try to discourage members from changing to a different type of coolant. I have HOAT in my PT Cruisers and change it with HOAT. It may be expensive but I have a peace of mind doing it.
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Last edited by ptcruisersteve; 02 Aug 2016 at 04:51 pm.
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Old 02 Aug 2016, 07:20 pm
Young Cruiser
 
Join Date: Mar 2015
Location: Liberty MO
Posts: 91
Default Re: Overheating and Diagnosis 101 – Non-Turbo PT Cruiser

Quote:
Originally Posted by deedra View Post
That is another thing - checking my garage floor like a crazy person over and over has yielded no coolant on the floor. The last time I drove my car was last week, the day after the check engine light came on. From the time that light came on til it was parked and not driven I drove a total of 16 miles. After the prior issues I wasn't taking any chances. I can tell you that it smelled like burnt krispy (if that makes sense) I also had it towed back to the mechanic bc I was not about to cause more damage not knowing what the problem is.
No wet spot on the floor and continued coolant loss could be from cooking. What I mean is the hot cylinder gasses are cooking the coolant and it blows off as steam under the hood.

The brown color and 'krispy' smell match what I've seen when green and orange are mixed AND cooking occurs. The one in my garage at the moment reminded me of this nasty odor.

You'll want to check for head gasket leaking per my original post.

Hope this helps.
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Old 02 Aug 2016, 10:18 pm
Obsessed Cruiser
 
Join Date: Aug 2014
Location: Thousand Oaks, CA
Posts: 7,298
Default Re: Overheating and Diagnosis 101 – Non-Turbo PT Cruiser

Quote:
Originally Posted by RCSnyder View Post
I have seen an abundance of posts regarding PTs overheating and a myriad of advice on how to diagnose, then repair. It seems that one single post should be able to answer most diagnostic questions (AND might be pinned for easy referral to forum members).

I’ll take a stab at the common issues:


#1 Failed Radiator Fan

Yes this is quite possibly the Achilles heel of PTdom. Fans often fail and their failure is not realized until the temperature needle hits the peg. Causes are generally (high-speed) motor windings, relay or wiring connection. Diagnosis is straight forward:

1. Check he fan’s motor operation (both speeds) with jumpers. Lots of posts with instructions, but it’s no more complicated than applying 12v to the windings via the connector and seeing what happens. Replace fan if either speed is inoperable. If windings are fine:
2. Check the main harness plug below the radiator for evidence of burn. If burnt, clean or repair as necessary to restore connectivity. If fine:
3. Swap around the relays. On earlier cars, simply move one known good relay to the fan high or low position in the power distribution center (earlier models) or swap relays mounted on the fan shroud (later models).

It is likely that one of the above checks will quickly identify what failed and put you on a corrective path. (If not, you have a one-off failure (ECU?) and may need the help of a dealer.)


Okay, so the fan is working properly, but it still overheats. Here’s where the advice is all over the map, and often contradictory. The first question must be “Under what conditions doe it overheat?” (I assume that most overheating conditions negatively affect coolant level in the radiator. For this reason, I’ll also assume that coolant levels have been topped off prior to any diagnostic.)


#2 Coolant Leak

If there is a wet spot on the garage floor or coolant present in the passenger footwell, you have a leak. A pressure test kit will help you isolate the source without burning yourself (in most cases). Replace the failed component (or components).

NOTE: To be clear, coolant boiling out of the overflow tank IS NOT a leak; it’s normal for an overheating vehicle to boil over/out wherever the system provides for such.


#3 Clogged System

If a PT overheats at idle – temp simply climbs from zero to overheat while idling – something is blocking the coolant flow or there is a leak in the system. Possibilities include:
- Stuck thermostat. This does happen but not as often as people might think. Replacing the thermostat is the old-school replacing things until something works approach. Before replacing the thermostat check the upper radiator hose. If the thermostat does not open (i.e. typical problematic stuck position), coolant does not flow through the upper hose, and it remains cool. If your car suffers from a cool hose, by all means consider replacing the thermostat.
- Blocked radiator. Radiator can become clogged for a number of reasons but flow checking is very easy while still on the car.
1. Disconnect upper and lower radiator hoses.
2. Shove the male end of a garden hose tightly into the upper hose port.
3. Turn on the water.
a. If the hose keep popping out of the upper port (i.e. lots of backpressure), the radiator may be at least partially blocked and need replaced.
b. If water flows freely, assume (for the moment) radiator is fine.


#4 Something Worse (but just as likely if the engine has been repeatedly overheated)

If PT overheats at speed, possibilities include:
- Partially blocked radiator. If there is any question, hold the thought and eliminate the next possibility before replacing the radiator. It may be the cause, but don’t spend that coin just yet.
- Leaking head gasket. Once a PT has been (severely) overheated, it is likely that the head gasket is failing BECAUSE the aluminum head is now warped and requires (as a minimum) resurfaced. (Sadly, many a PT has found its way to the recycler because owners are scared at the cost of this repair. Even more sadly, they further damage their cars by dumping all sorts of canned remedies into the radiator, believing that product X will actually seal a leaky head gasket.)
• Before going any farther, it might be useful to describe the symptoms of a failed head gasket on a PT because this is where much confusion exists.
1. A failed head gasket rarely manifests itself as ‘milky’ oil or exhaust steam. Both symptoms only manifest when coolant (@16psi) is escaping the water jacket into the cylinder (uncombusted at @160-170psi) or oil passages (@0psi).
2. The symptom common to PTs is cylinder gas pushing past the head gasket into the water jacket. It blows (very) hot gas into a liquid, cooking the liquid and bubbling out through the coolant overflow.
• Testing for such a leak cannot be done with the previously mentioned pressure test kit because that kit cannot duplicate the types of pressures causing the leak (>160psi uncombusted) nor the direction of leak flow (i.e. cylinder to water jacket). Testing is most reliably done with a combustion leak test kit (e.g. Lisle 75500 Combustion Leak Detector available from Amazon.com for <$60). Follow the directions with the kit, looking for the blue fluid to turn yellow if a leak is detected. If the PT tests positive, the head must be pulled and redecked, as a minimum.


#5 Something Else?

• But what if my PT overheats at slow speeds but is fine at highway speed? Low speed overheating is almost always a blockage issue. See ‘overheats at idle’ above.

• But my PT always overheats. What about me? Start with the ‘overheats at idle’ scenario and work from there. You’ve got to be sure the basics are working first, and if the cooling fan is not doing its job, nothing else really matters.

Hope this helps.
First thing I would do is do an coolant compression check. This would be after you flush out the sludge and get the restrictions out of the engine coolant system. You must keep your engine coolant system sealed and flowing properly. This is not about just looking for coolant leaks. This is about making sure your coolant system is at the correct pressure to keep the boiling point of coolant down. If you choose not to do the coolant pressure test you might be wasting time and money. Also check your radiator cap.
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Last edited by ptcruisersteve; 02 Aug 2016 at 10:25 pm.
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Old 03 Aug 2016, 11:22 am
Fresh Cruiser
 
Join Date: Aug 2016
Posts: 6
Default Re: Overheating and Diagnosis 101 – Non-Turbo PT Cruiser

This was done yesterday though I have not picked up my car yet from the mechanic so hopefully the issue is fixed. On the 28th my check engine light came on and the mechanic told me last night that the code coming up is P0601. Looks like I will also be replacing the computer...
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Old 04 Aug 2016, 01:25 pm
Young Cruiser
 
Join Date: Mar 2015
Location: Liberty MO
Posts: 91
Default Re: Overheating and Diagnosis 101 – Non-Turbo PT Cruiser

Quote:
Originally Posted by ptcruisersteve View Post
First thing I would do is do an coolant compression check. This would be after you flush out the sludge and get the restrictions out of the engine coolant system. You must keep your engine coolant system sealed and flowing properly. This is not about just looking for coolant leaks. This is about making sure your coolant system is at the correct pressure to keep the boiling point of coolant down. If you choose not to do the coolant pressure test you might be wasting time and money. Also check your radiator cap.
Those topics, Steve, would be covered in the second semester offering "Overheating and Diagnosis 102."

I intentionally assumed people had PTs which were operating normally and began experiencing overheating issues. Sludge, and the like, as you know are generally the result of having been overheating and making a misstep (e.g. topping of a HOAT-filled system with green juice) or using some sort of stop-leak. My hope in writing this was to help people not make such a mistake with a methodical approach to problem solving.

As for the radiator cap failing? Just finished the 7th PT in the last year and a half and haven't seen a bad radiator cap that didn't immediately identify itself as faulty. So, I hope you can excuse my dismissal of it as a potential - and common - cause of PTs overheating.

Bob
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