Toyota MR2 Message Board - View Single Post

tjmr2 · 12-22-2008, 01:10 AM

The head has valve guides and valve seals.

The valve slides up and down inside the valve guides and the tolerance between them and the guide is critical. Too much clearance and the valve won't seat properly, can wear your valve and seat = bad juju.

The valve seal sits on top of the valve guide in the head, and seals the intake manifold vacuum or exhaust manifold pressures from the oil gallery of the head. The seal hides under the shim and bucket so you have to take the cams out to see them.

A bad valve seal can allow combustion gasses into the crankcase, or place a large vacuum on the crankcase, thus looking like massive ring blow by accompanied by dirty oil and high oil consumption. Good for killing mosquitoes, bad for cool factor if your girl friend is following you.

I had 1 bad intake valve seal. Started off with a small puff of smoke at high RPM, like 2nd to 3rd. 10k miles later I was blowing through a quart of oil in 120 miles.

Tore that engine down to pieces, thinking I had a bad ring. All I found was the bad intake seal and some damage to the valves and seats from the excessive carbon. That's how I ended up with my Black Top.

Run a leak down test to determine the problem. It's an inexpensive tool to make and while a pain to do in the car it will tell you where the problem lies before you start tearing everything apart and spending money. Here is a link, you can google more.

Building and Using a Cylinder Leakdown Tester

Just my 2 cents worth, all too often people look at an immediate problem and are only willing to spend money to fix it. They are in a hurry, and to pay the mechanic more than is necessary seems like a waste of money. Personally if I pull the head thinking I've got a bad head gasket I'm also checking all valves, valve guides, and installing new seals everywhere in the head. If I spend a couple of hours and maybe another hundred dollars in seals and don't have to go back into an engine to replace a seal that I could have replaced six months ago it's money and time in the bank.

Guess what I'm saying is spend the extra money and do the job right the first time. Costs you less in the long run.

Good luck.

12-22-2008, 01:10 AM	#5 (permalink)
tjmr2 Cage Fighter Join Date: Jan 2008 Location: Colorado Posts: 409 Thanks: 0 Thanked 62 Times in 59 Posts My Google Map iTrader Rating: (0/0% )	The head has valve guides and valve seals. The valve slides up and down inside the valve guides and the tolerance between them and the guide is critical. Too much clearance and the valve won't seat properly, can wear your valve and seat = bad juju. The valve seal sits on top of the valve guide in the head, and seals the intake manifold vacuum or exhaust manifold pressures from the oil gallery of the head. The seal hides under the shim and bucket so you have to take the cams out to see them. A bad valve seal can allow combustion gasses into the crankcase, or place a large vacuum on the crankcase, thus looking like massive ring blow by accompanied by dirty oil and high oil consumption. Good for killing mosquitoes, bad for cool factor if your girl friend is following you. I had 1 bad intake valve seal. Started off with a small puff of smoke at high RPM, like 2nd to 3rd. 10k miles later I was blowing through a quart of oil in 120 miles. Tore that engine down to pieces, thinking I had a bad ring. All I found was the bad intake seal and some damage to the valves and seats from the excessive carbon. That's how I ended up with my Black Top. Run a leak down test to determine the problem. It's an inexpensive tool to make and while a pain to do in the car it will tell you where the problem lies before you start tearing everything apart and spending money. Here is a link, you can google more. Building and Using a Cylinder Leakdown Tester Just my 2 cents worth, all too often people look at an immediate problem and are only willing to spend money to fix it. They are in a hurry, and to pay the mechanic more than is necessary seems like a waste of money. Personally if I pull the head thinking I've got a bad head gasket I'm also checking all valves, valve guides, and installing new seals everywhere in the head. If I spend a couple of hours and maybe another hundred dollars in seals and don't have to go back into an engine to replace a seal that I could have replaced six months ago it's money and time in the bank. Guess what I'm saying is spend the extra money and do the job right the first time. Costs you less in the long run. Good luck.