Occasionally blows blue smoke when first started

DANGO1964

MEMBER
1999 LEXUS RX 300
4.7L
V6
4WD
AUTOMATIC
130,000 MILES

It blows blue smoke when first starts occasionally and then typically stops completely. The motor sounds and runs very good but this does happen about every six times it’s started. I read these motors have a reputation for building up sludge and check engine light is on steady but other than that it runs very well and it was a half quart of oil low when I bought it a few weeks ago and hasn’t really used any since. I know the car sat for a while before I bought it and the check engine light came on within the first 20 miles it runs and sounds great. So I’m not sure what is up with it.

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

Often times a small amount of blue smoke at start up is the result of bad valve seals. Also, if the cylinder heads aren't allowing oil to drain back into the oil pan fast enough and it builds a small amount of oil under the valve covers, that can happen as well.

What condition is the oil in presently? Is it clean?

Let me know.
Joe

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Tuesday, June 16th, 2020 AT 7:27 PM

DANGO1964

MEMBER
5 POSTS

The oil does appear to be clean, but I’m going to change it anyway since I just bought 2 weeks ago so I want to start a maintenance schedule. I read up on this particular engine and I’m concerned there is sludge built up. I’ve just never done it but if it keeps the motor going good it’d be worth it. What do you think? Like I said earlier it only happens once every 3rd or 4th day then doesn’t do it again until a few days later and it’s only the initial start up for the day. It sat for a couple years so I would understand if some seals dried out. What do you think? I thought about putting some Winn oil treatment in and see if that cleans it up. It runs and sounds great the smoke surprised me. Thanks

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Tuesday, June 16th, 2020 AT 7:45 PM

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

I think that is a great idea. Do me a favor. Check the condition of the oil prior to changing it. Then once it's changed and you drive it for a few miles, check the condition again. If it looks dirty very shortly after changing it, then the inside of the engine is dirty as well. There are detergents in the oil that help keep things clean. If there is a lot of build up or dirt, it will show quickly.

As far as the drains in the cylinder heads, you would need to remove the cylinder head covers and then inspect the drains in cylinder heads. I was not able to find a pic that was simple and to the point, but I did find an exploded view of the cylinder heads. I circled the covers that need removed and highlighted the cylinder heads. This will at least give you an idea as to what has to come apart for inspection. Please don't pay attention to all the parts indicated in the picture. Only the covers need to be removed.

Let me know what you find and if you have other questions.

Take care,
Joe

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