87 4x4

drove my truck home from work about 30 miles shut it off. at this point everything seems normal. it sits for about 15 minutes and i go out to grab something to eat. fire it up it was misfiring a bit but i figured i flooded it because i always seem to hit the gas pedal getting in. but i get moving and a hideous sound come from under th hood.

it sounds like a knock but coming from the top end. it sounds as if its running on 2 or 3 cylinders. i pulled the valve cover gasket and everything seems fine.
it is not making the noise at idle just when you step into the gas. any help would be greatly helpful.

87 4x4 pickup with 193,000 miles no milkshake

sam333

Do a compression test.

INFINITY

X2 have repaired a vehicle like this. blown headgasket between cyl. 1 & 2. sounds like a marble inside of a drum.

xxxtreme22r

how can anyone diagnose a noise in anything accurately without a video? Especially on a 22r/re/rte which are noisy motors to begin with.

And a blown head gasket doesn't sound like anything. It's silent.

smrflng

Not that you would want to hear this but it might be a partially sticking valve. But like sam said a compression test will let you know. How many miles are on the engine? It could also be bad timing chain guides. The chain will be bouncing off of the cover which will make a awful noise and it will run crappy if the upper gear jumps a tooth.

Russ

xxxtreme22r

compression test will not tell you you have a bad valve, only a leakdown test will tell you that.

looks like I need to make a sticky on what compression tests, leak down tests, vacuum tests etc etc tell you.

smrflng

An automotive stethascope is a great tool when it comes to trying to find out where the noise might be coming from as well.

Russ

sam333

Its not the ideal( not even with canned sound).
Compression test will tell you if you have some part of the cylinder/ head that is not sealing, not which, but will tell you if you need to look further.
Leakdown will tell you what area to look at.

Please bless us with your wisdom.

xxxtreme22r

I'm sorry I should have quoted with that reply. Was not trying to discount doing a compression test. Just that the compression test wont tell you directly that you have a bad valve.

Never heard of any headgaskets making odd sounds in a motor. And I have repaired many bad headgaskets.

If anything it would cause an engine ping. Which is not a knock. But to someone who's not familiar with any type of abnormal engine sounds it can the a knock. Which is why to diagnose any type of sound on the internet is hard with just a description, let alone with no video whatsoever.

One person's tap is another person's knock, one person's heavy metal knock is another person's light metal knock. And so on.

Now as far as a compression test, usually a single cyl that has low compression would most of the time mean a bad ring, an improper sealing valve. Does not nec mean the valve is bad, but can also indicate a bad valve seat, bad valve spring or a flat cam lobe. It might also be a cracked head, but I have personally yet to see that not with just one cyl low.

Two adjacent cyl with bad compression is usually a head gasket but can also be a cracked block and/or head.

All cyl low compression usually means either worn rings or slipped timing chain/belt depending on how low the cyl pressure is.

Now there are two ways to do a leak down test. he right way and the back yard way. The backyard way is to add some oil to the cyl via a spark plug hole. If compression test goes up that usually indicates a bad ring. If compression test stays the same it can mean an improperly seating valve as described earlier.

The correct way is to add pressurized air to the cyl via the spark plug hole. You can then hear where the air is coming from. If you hear air escaping through the intake then that most likely indicates that an intake valve is not sealing properly for the same reasons as previously mentioned.

If you hear the air coming from the exhaust pipe then that would be an improper sealing exhaust valve.

If you hear the air coming from the dipstick tube then you have bad rings.

You can combine several of these tests to narrow each possible result to one. But I think I have said enough.

sam333

To the op, the reason I suggested a compression test is abnormal engine noise plus missing, makes me suspect engine mechanical problems( valves /pistons) rather than electrical or fuel.But based on internet info, its really all guessing( hopefully educated guessing).

xxxtreme22r, I agree that leakdown tests are more usfull/ accurate ( thats all I use), but most people dont have compressors, and leakdown testers have not been( and still are not widely) available at most auto parts stores.

87 4x4

i will work on compression test tomorrow. i had my dad crank the motor with the coil wire pulled and all the valves seem to be opening. i will do the compression test then fire it up tomorrow hopefully and we can figure this out.

87 4x4

Bump.

INFINITY

wow, sounds like you have seen/heard EVERY possible thing in your life. with that said, you most defiantly were not along side me when i tore completely apart a 22re with a loud knock in the top end. and yes it was a blown headgasket between 1 and 2. nothing else was wrong with the motor it was a fresh rebuilt motor just as all of the internals showed, just a blown gasket.

please do not say something is when you are not certain, this creates misinformation for the next person.

xxxtreme22r

And I did add if anything it will cause an engine to ping. A heavy ping will sound like a knock to some people, but it's not. Explain to me how a headgasket causes a real knock in a motor when it blows between cyls. I wanna hear this.

To add to this, if the headgasket is bad enough between cyls, I can also see it blowing exhaust from one cyl into the other and then out the intake valve. Not sure what that would sound like, but it's not a knock.

A motor knock is two metal objects hitting together. Most likely harder than they are supposed to be. A blown headgasket is not two metal objects hitting one another..

Maybe me saying a blown headgasket is silent was not 100% correct, but a blown headgasket will not cause an engine to knock, unless you had over heated it or hydrolocked it and it took out a rod bearing or bent a rod or something else. In which is a blown headgasket AND a spun rod bearing. Using your theory in this just changing a headgasket will NOT remove the knock in which you say a blown headgasket can cause.

87 4x4

So I did a compression check. One of the cylinders was low. But the checker I used was old and didn't give very good readings on the better cylinder but this motor clearly has a bad cylinder. Could a bad head gasket cause this? I believe the valve train is fine and dandy. Maybe the yota is just tired and needs a rebuild. What do I need completely? I seen a master rebuild kit for 299.99.

xxxtreme22r

yes a head gasket can cause that, however, so can a bad valve or a bad ring. Now you can do a leak down check on that cyl. 2 ways to do it. As stated earlier. If you do it the free way first with oil put into the spark plug hole and the compression goes up then it's rings. If compression stays the same then it's either a valve or a headgasket. Which means if you did the leakdown with the oil put into the spark plug hole, then you must do a full leakdown with pressurized air to tell where the air will come from.