Engine overheating

Tiny
LEXI350
  • MEMBER
  • 2007 LEXUS IS
  • 3.5L
  • V6
  • RWD
  • AUTOMATIC
  • 156,000 MILES
I just bought this car it is the 350 model. I drove the car for two hours and temperature gauge spike up near the red zone, pulled over to safe place and managed to get home safely after makes few stops when it start over heating. Took the car to the shop and replaced the radiator and thermostat, drove ten minutes from the shop it start over heat again. We did 'burp" the system, took a car for test drive to see if it was fixed. Drove it two hours without over heating and left it cold for twelve hours. Checked the coolant level next day very low and top it off. Problem: coolant missing without trace, there was white smoke from tail pipe when cold start. Misfire on bank 1 cylinder 2. Also, on the cold start the CEL flashing for few minutes and stay lit as the engine warm.
Mechanic suggest head gasket leaking. I do not see any symptom of head gasket leaking such as milky oil, did block tester and the result is negative.
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Monday, April 24th, 2017 AT 9:14 PM

9 Replies

Tiny
CARADIODOC
  • EXPERT
Milky oil is the most rare symptom of a leaking cylinder head gasket. The most common symptoms are white smoke from the tail pipe and unexplained loss of coolant.

The problem with the chemical test at the radiator is the problem has to be acting up during the test. If the overheating is intermittent, any testing has to be done during that time. Since this does not happen all the time, you might add a small bottle of dark purple dye to the coolant, then check a day or two later with a black light. The dye will show up as a bright yellow stain that you can follow back to the source. If the head gasket is leaking, you will find the dye inside the tail pipe.

Auto parts stores will have the dye, and those that rent or borrow tools should have a black light.

Also be sure the radiator fan is turning on. If it is not working, the engine will only overheat at low speeds or when the car is not moving.
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Monday, April 24th, 2017 AT 10:04 PM
Tiny
LEXI350
  • MEMBER
Update : I have been doing test by driving the car until normal temperature or until the fan kick in, I drove the car about 2 hours and the temp needle stayed below the middle, then I parked the car all night and the next morning I opened the radiator cap and the it showed low coolant, I topped it off and do the same cycle ( warming and top off ) in hopes that air pocket has filled with coolant thereby lowering the coolant level, there was no significant coolant loss from the first and second test, when I did the third test on 20 minutes driving the coolant expelled / spewed from the little hose in the tank reservoir. With all being said, could it be head gasket blows the combustion pressure into cooling system or maybe the cooling system problem?
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Thursday, April 27th, 2017 AT 4:12 PM
Tiny
KEN
  • ADMIN
Hello,

This sounds like a blown head gasket that is not showing up in the chemical test which is normal becasue the chemical test only catches about 60% of the blown head gaskets.

Please let us know what happens.

Cheers, Ken
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Monday, May 1st, 2017 AT 2:01 PM
Tiny
CARADIODOC
  • EXPERT
Here's something else that might work. If one of the symptoms is losing coolant, you can add a small bottle of dark purple dye to the coolant, then check a day or two later with a black light. The dye will show up as a bright yellow stain. If you find that dye inside the tail pipe, suspect the head gasket.

Auto parts stores will have the dye, and those that rent or borrow tools should have a black light.
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Monday, May 1st, 2017 AT 9:20 PM
Tiny
LEXI350
  • MEMBER
Hi all, I took the car to local shop to get compression test and mechanic confirmed the head gasket leak, The head gasket done week ago and the car no longer over heat and the temperature stay below the middle mark. Few minutes after drove the car from the shop the CEL came back on and flashing, whenever I restart the engine it stay lit and flashing again after a while. Took it back to the shop back and forth, the code set P0174 ( system to lean ) and P0300 ( random misfire ). Replace the spark plug, check all the injectors are seem to be fine and did what they call wet compression test that confirmed low compression on cylinder no 1 and no 2, the rest of cylinder tested has the same pressure. With all that said the mechanic concluded that the pressure discrepancy causing the misfire and was caused by failed or bad piston ring on those cylinders. Now, the mechanic told me that in order to replace the piston ring he need to redo the head gasket again at my cost, blahhh. Anyone has any thought about this whole situation, could it be the mechanic liability as he failed to identify the piston ring problem when diagnosed the head gasket at the first place or at least check the possible related issue before putting the engine back? Now I have to pay again head gasket replacement plus cost to replace the piston ring?
Any suggestion greatly appreciated.
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Friday, May 26th, 2017 AT 12:36 PM
Tiny
KEN
  • ADMIN
I would take it to another shop becasue if the head gasket has blown it could make the 1 and 2 cylinder low the same amount and the rings are fine.

Please let us know what you find, I am curious ;)

Cheers, Ken
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Friday, May 26th, 2017 AT 2:16 PM
Tiny
CARADIODOC
  • EXPERT
Yup. Also be aware worn piston rings are not real common and have to be real bad before they'll cause a misfire. To make matters worse, you can't expect your mechanic to identify worn rings when there is already a more common cause that has been diagnosed. You would scream that he is wasting your money by continuing to perform more tests after a cause had already been found. That would be like finding a nail in your tire that is causing it to go flat, but you continue to spend hours looking for additional causes for the same problem. Why would you do that? And would you fault anyone for not continuing to look for more leaks when you're paying that person by the hour? You've already found the overheating problem has been solved, so something had to have been done right.

There are at least five things that can cause low compression. A compression test only identifies that compression is low in a cylinder, not why. Compression tests take about a half hour, but if standard procedures aren't followed, the last cylinders tested will test lower than the first ones because the test requires cranking the engine while it's still warm. When the last cylinders are tested, the battery has become run down a little so the engine will crank slower. The engine has cooled down, so the pistons are designed to shrink to a slightly oval shape. That can reduce the rings' ability to seal. Your mechanic could have your best interest at heart, but the guy at the next shop might test the cylinders in a different order, might know to use a battery charger, and might complete the testing while the engine is still warm. His results could vary from the first mechanic's results, while nothing changed in the engine.

Once it was believed two cylinders were low in compression, a more thorough cylinder leakage test would identify why that was so. That test takes a considerable amount of time to set up for one cylinder, then it has to be done all over again for each additional cylinder. During the test, the percent of leakage is indicated on the tester, and the mechanic can identify the cause of excessive leakage by listening in various places. If an exhaust valve is leaking, there will be hissing heard at the tail pipe. If an intake valve is leaking, you'll hear the hissing at the throttle body. If the piston rings are leaking, the hissing will be heard at the oil cap or the dip stick tube. If the head gasket is leaking, you may see a stream of tiny bubbles in the radiator. The often-overlooked clue when two adjacent cylinders are leaking is you may hear hissing from the spark plug hole in the cylinder right next to the one being tested.

The problem with a leaking head gasket is they don't always leak all the time. Some only leak when the very high pressure shows up from the burning fuel while the engine is running. Some leaks only show up when the engine is stopped, but there's still some pressure in the cooling system.

I too would get a second opinion from a different shop, but I wouldn't tell them where the previous work was done. If the people at the two shops are friends, they may tend to look out for each other and minimize the seriousness of a mistake. If they're on unfriendly terms, the people at the second shop may go to great lengths to make it sound like the previous mechanic did shoddy work, and that could be the furthest thing from the truth.

If it is found the low compression is due to another leaking head gasket, you can expect the first shop to do that part of the job over at their expense. I was never angry with a customer if I had to do something over. I was embarrassed and apologetic, and I was twice as careful the second time. My service manager often gave the customer some freebies, like free oil changes, or a gift certificate to a nearby restaurant, to make up for their inconvenience of having to come back a second time.

I still take issue with the diagnosis for the misfires. Code P0300 suggests all the cylinders are misfiring at times. That can be caused by a weak ignition coil, (for engines that still use a single coil), low fuel pressure, or anything else that affects the fuel / air mixture for all the cylinders. If your misfires are to be contributed to the low compression, you'd have fault codes for cylinder number 1 misfire, (code P0301), and / or cylinder number 2 misfire, (code P302). When a code is set for a single cylinder, an easy trick is to swap places between that and one other cylinder for the spark plug, and that cylinder and yet a different one for the injector, erase the code, drive the car, then wait to see if a misfire code sets for the cylinder you moved one of the suspect parts to. That can be done rather easily too for the ignition coils on those engines that use individual coils for each cylinder.

The "lean" fault code can be the result of spark-related misfires because unburned fuel and oxygen are going into the exhaust system where the oxygen is detected by the oxygen sensor. On any car other than Chrysler products, a leak in the fresh air tube between the mass air flow sensor and the throttle body will allow air into the engine that is not seen in the measurements, so no fuel will be included in the calculations. That extra air will divide up evenly among all the cylinders and can result in random misfires and the "lean" code. The fix for that can be as simple as tightening a hose clamp.

This all boils down to getting that second opinion, and I have a strong suspicion the repair is going to be much less serious than new piston rings.
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Friday, May 26th, 2017 AT 4:03 PM
Tiny
LEXI350
  • MEMBER
Thanks for all great advise and recommendation, I have scheduled to get more comprehensive diagnosis to lexus specialist, will post the result.
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Saturday, May 27th, 2017 AT 9:42 AM
Tiny
KEN
  • ADMIN
Please do!
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Saturday, May 27th, 2017 AT 12:13 PM

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