ToyotaFanz

2000 lexus es300 that is overheating cause by the intake manifold gasket

seanddd

First, how would an intake manifold gasket go bad by itself? Did you remove the intake but didn't replace the gasket when putting it back in? 2nd, are you talking about the top or the lower (2 pieces) intake manifold gaskets?

BDSL

The intake manifold gasket is metal for a reason. Stick with metal gasket.
Plastic/rubber gasket would risk being sucked into the cylinders....

ToyotaFanz

The original problem was started with error codes PO 325 and PO330. Both are knock sensors which when bad. In getting to the knock sensors, removal of the intake manifold is necessary. The knock sensors were replaced with new ones along with all new gaskets, hoses, solenoids, and many other new parts that were safe to replaced since the job getting to the knock sensors was so labor intensive and time consuming. Valve cover gaskets and major tune up were also done. The knock sensors and intake gaskets have been replaced twice and the overheating has been going on "off and on" since last October 2017. I am extremely puzzled about where the leakage is. I have changed hoses, intake gaskets, check other overheating causes such as water pump, thermostat (which is new also), heater core, etc. and can't pin point or verify the cause of the overheating. It has been diagnosed by 2 professional mechanic shops and repaired twice by two mechanic shops and the problem won't go away. So I did all the labor myself this time to see for my self if all new parts were replaced. When I got to the gaskets, and I saw no sealant on them, I wondered if that had been left off and maybe should have been used and that would explain why the car keeps loosing fluid and evenly overheat. Some have guest that it might be the head gasket causing the leak, but I do not have the symthoms of a head gasket leak. Anyone have any ideas as to what I need to do next or which way I should proceed in solving this overheating problem?

seanddd

If you don't find wetness or puddle of coolant under the car, it must have been leaked into the engine. But have you determined that the overheating is due to loss of coolant? At what rate is the coolant going down? Have you checked thermostat? To me, you should never use RTV on intake gaskets, also make sure you use the genuine toyota gaskets and the bolts around the lower intake block are torqued to spec and tightening pattern is followed.

seanddd

NVM about the thermostat...

seanddd

Hope you also changed the knock sensor wiring harness when you were at it,.

ToyotaFanz

Thanks for your comments and also for replying so quickly. The coolant piles up underneath the coolant bypass hose underneath the intake manifold and plenum. the coolant builds up and starts flowing over the canal where the knock sensors are located. Most of the time when it leaks and then overheat, the coolant flow toward the drivers side of the engine then to the ground. Sometimes it flows to the passenger side and then runs down by the water pump. Either way, there is puddle of coolant on the ground. I decided to tackle this job myself and removed all the parts over the coolant bypass hose (as well as the bypass hose itself) and visible look at the coolant sitting in that canal between the intake manifold holes (for lack of not really knowing what to call it). I have lots of pictures that I took as I attempted this type of car repair for the first time. I know the coolant is not leaking inside into the engine. Coolant lost start at maybe a gallon every 2 weeks and finally escalated to about a gallon every other day.

ToyotaFanz

Yes, I did change the knock sensor wiring harness. It makes perfect sense to change all 3 parts at the same time because of the difficulty and labor intensity of getting to those parts.

ToyotaFanz

not sure what you mean by NVM?

ToyotaFanz

I am new to this site, but I am going to try to attach some pics . . .
As you can see in one of the pics, I socket (12mm) and ratchet extension fell underneath the coolant bypass hose when I was disassembling the intake manifold. the only way to get it out was removal of the hose so I could get to it.

seanddd

Don't use Fel-pro, stay with OEM, also the torque and torque sequence are important, it should be a in a crisscross pattern starting from the center, also re-torque in 2 hours because the sealing material will bed in. Make sure the center hose connections (in one of your pictures) are tight with no leaks.

seanddd

NVM=never mind. I missed your mentioning the thermostat already.

seanddd

Look for any hair line cracks in the aluminum blocks and hose connectors too.

ToyotaFanz

Also I want everybody to know, I tried the over the counter liquid sealant from Auto Zone. Blue devil, I tried twice and Bar's Leak I have tried once. They both worked, but only temporary. They never permanently fixed the problem.