Bad exhaust valve or not ??

[Mellemel]

On a recent visit to the mechanic, he said he was pretty sure I have a bad exhaust valve, so before I decide to take the head off has anyone put in some valve oil seal conditioner ? I once used a product made by "Wynns" when I had this problem on a vehicle which cured it, but that was over 20 years ago now. That stuff was a purple jelly stuff.

However, yesterday I went on a long drive at a steady 115km/h down the highway for 90 mins one way then back again, 4rnr ran awesome and I have not used any oil ! I thought I would have used some oil if I had a bad exhaust valve !

Might it be something else ? Today I had a bad cold start, misfire, banging and clattering and a huge smoke show for about 3 minutes !! After this it ran great.

Did I dislodge some carbon, might have done some good in that respect then !

 

[LittleCaesar]

What color was the smoke? Blue or white? The former usually indicates oil getting in the top somewhere it shouldn't. The latter indicates coolant getting somewhere it should not.

You could start by changing your PCV valve with another new OEM one.

This stuff also works well though I have never used it in a 4runner before:
https://www.amazon.com/Liqui-Moly-2020-Motor-Saver/dp/B00CPL8WY8

 

[baja1]

On a recent visit to the mechanic, he said he was pretty sure I have a bad exhaust valve, so before I decide to take the head off has anyone put in some valve oil seal conditioner ? I once used a product made by "Wynns" when I had this problem on a vehicle which cured it, but that was over 20 years ago now. That stuff was a purple jelly stuff.

However, yesterday I went on a long drive at a steady 115km/h down the highway for 90 mins one way then back again, 4rnr ran awesome and I have not used any oil ! I thought I would have used some oil if I had a bad exhaust valve !

Might it be something else ? Today I had a bad cold start, misfire, banging and clattering and a huge smoke show for about 3 minutes !! After this it ran great.

Did I dislodge some carbon, might have done some good in that respect then !

this was after the seafoam treatment yes?

 

[Mellemel]

Correct, the seafoam I added was over a week ago and a few Km's ago too. I thought the smoke was from that still, but yesterdays Highway run of around 250km's was smokeless all the way until todays start up.

The smoke today was whitish gray for around 2-3 mins then suddenly all stopped.

I keep thinking I might have a HG leak due to coolant loss still, but I am running at 86-88c coolant temps constant now with my new rad and no overheating issues at all and no loss of power. I had to add almost 2 pints of coolant today, but I also had a split hose that I found, that's probably why.

 

[JayRolla]

Have a leak down test done, this will tell you if a valve is bad and leaking. Compression check also should be done. If the mechanic is saying you have a bad valve im sure these tests where already done?

 

[UnderFire]

Rough idle and white smoke is usually a head gasket issue, you may also have some noise that sounds like a bottom end lnock especially on a cold start from coolant pooling in the cylinders trying to be pushed out. Valve seals are normally just a little blue smoke and oil burning smell. You'll burn through coolant pretty quickly unless its just barely seeping into one of the cylinders.

 

[alumarine]

It's winter where you are right?
You'll get "smoke" on start up when it's cooler out.

 

[baja1]

can a mechanic tell you more about a bad exhaust valve, bent, broke, burned, stuck, collapsed....whats next, will more seafoam treatment maybe help?

 

[Toyotayoda]

On a recent visit to the mechanic, he said he was pretty sure I have a bad exhaust valve, so before I decide to take the head off has anyone put in some valve oil seal conditioner ? I once used a product made by "Wynns" when I had this problem on a vehicle which cured it, but that was over 20 years ago now. That stuff was a purple jelly stuff.

However, yesterday I went on a long drive at a steady 115km/h down the highway for 90 mins one way then back again, 4rnr ran awesome and I have not used any oil ! I thought I would have used some oil if I had a bad exhaust valve !

Might it be something else ? Today I had a bad cold start, misfire, banging and clattering and a huge smoke show for about 3 minutes !! After this it ran great.

Did I dislodge some carbon, might have done some good in that respect then !

Engine mechanical doesn't just fix itself. If you do in fact have a burn't exhaust valve you will have a very consistent misfire, blue/black smoke, perhaps white, maybe even a p0172 which indicates rich fuel mixture. No need to disassemble an engine to find out if you have a bad valve, or poor sealing piston rings, or even a blown head gasket/warped head, a cylinder leak down test can be used to identify all of these problems. If your engine has good compression(meaning you checked all the cylinders compression with the engine hot) and compression doesn't vary more than 10% between the best and worst cylinders, you are chasing a fuel or ignition issue and not a mechanical issue.

 

[GrassFed]

Easy to test an exhaust valve that isn't sealing. Hold a dollar bill to the exhaust pipe and if it tries to suck it back down the pipe you're in bad shape.

Only from experience do I know this. :moping:

 

[gamefreakgc]

Easy to test an exhaust valve that isn't sealing. Hold a dollar bill to the exhaust pipe and if it tries to suck it back down the pipe you're in bad shape.

Only from experience do I know this. :moping:

This is pretty true. Or it also could be a cylinder or two is not firing (was in my case on a fixer-upper I bought).

A bad exhaust valve would not blow smoke. You'll just lose compression and power, all it means is that unburnt fuel and oxygen exits the combustion chamber before fully igniting. If you have smoke, it's a totally different issue. I had two exhaust valve that were not seating all the way and I had very low compression in those two cylinders. Did a valve adjustment and worked perfect afterwards.

Sweet smelling smoke is coolant, darker-blue smoke is oil, black smoke is too much fuel. If you are burning oil, your piston rings are no good and you might want to look into a rebuild or a new engine. Once again, bad valves lose compression (someone suggested a leak down test, have your mechanic do this), they don't blow smoke.

 

[mtbtim]

Have a leak down test done, this will tell you if a valve is bad and leaking. Compression check also should be done. If the mechanic is saying you have a bad valve im sure these tests where already done?

Yes, first do a compression test to find which cylinder(s) have low compression.
This is supposedly what the FSM recommends for cylinder pressure:
174psi or higher
145psi Minimun
Difference between cylinders 15psi

Next, have the mechanic do a leak down test of the bad cylinders. Each cylinder he tests when doing the leak down test has to be at TDC (top dead center so both the intake and exhaust valves are closed). The mechanic pressurizes the cylinder to see what percentage loss it has. Then he has to investigate where the pressure is going. He can listen for air at the throttle body to see if it's a leak at the intake valve. He can listen for air at the exhaust tail pipe to see if it's a bad exhaust valve. He can open the oil fill cap and listen for air to see it's worn piston rings and finally he can open the radiator cap and look down into the radiator for bubbles that will tell him if it's a bad head gasket. If two cylinders next to each other are bad, it's most likely a head gasket leak between the two cylinders.

If it's a bad valve, maybe it's worth replacing the heads. If the piston rings are toast, you're probably better off getting another engine.

 

[mtbtim]

I had two exhaust valve that were not seating all the way and I had very low compression in those two cylinders. Did a valve adjustment and worked perfect afterwards.

Did you do this valve adjustment yourself? If so, did you do a write-up of how you did it?

 

[Mellemel]

The only thing I have done is add seafoam thus far. The mechanic two weeks ago did a compression test and after that he said he was sure it was a bad exhaust valve not a HG. The cylinders pressure were 180, 150, 190, 250, 180 and 180. He said if it was a HG problem then the numbers would be low on the adjacent cylinder and they aren't !

The banging and knocking at start up is from the top not the bottom of the motor. The motor hunts when misfiring only for 30 seconds max then idles fine.

Going to start her now after sitting all night. Fingers crossed.

 

[LittleCaesar]

With those numbers something is going on. 150 is too low for the others and 250 is way too high, maybe a bad reading.

Have your mechanic perform a leak down test.

 

[gamefreakgc]

Did you do this valve adjustment yourself? If so, did you do a write-up of how you did it?

Unfortunately no, it was probably one of the most frustrating jobs I've done to date. Ranks #2 behind the valve body upgrade I did LOL.

 

[mtbtim]

Unfortunately no, it was probably one of the most frustrating jobs I've done to date. Ranks #2 behind the valve body upgrade I did LOL.

It's looks like it could be a frustrating job. I bought a set of tools by Lisle and was thinking I might try this one day. If I do, I guess there will be plenty of cursing in Timmy's garage that day.

 

[baja1]

im trying to wrap my head around this.....if you use a seafoam treatment that loosens up and removes carbon build up from valves that use a bucket/shim for adjustment.....won't you end up with more slack and a noisier valve train?

 

[gamefreakgc]

im trying to wrap my head around this.....if you use a seafoam treatment that loosens up and removes carbon build up from valves that use a bucket/shim for adjustment.....won't you end up with more slack and a noisier valve train?

In theory, but if your engine ever had so much carbon build up that it affected your valves that much then YIKES something is probably terribly wrong with that engine.

 

[baja1]

In theory, but if your engine ever had so much carbon build up that it affected your valves that much then YIKES something is probably terribly wrong with that engine.

gracias! then how does seafoam quiet the valve train.....or does it?