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When changing head gasket is it necessary to also change the valve stem seals ???

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It is not strictly necessary on most cars if the engine has not been burning oil from worn seals there. On some newer cars gaining access to these seals can be quite difficult even after lifting the head. On others it is much easier. Then on some engines like Hyundai Excels you virtually have to because it is such a weak spot.

So if you can without too much trouble it is a good idea.

Posted on May 19, 2017

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Posted on Jan 02, 2017

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2002 Subaru impreza ts 2.5 when driving down the road and let off the gas and coast then get back into it it smoke bad for a few minutes then clears up until you coast again. Is it the head gasket


no
when you are coasting , the inlet manifold vacuum can exceed 25 " mercury and that puts extra strain on the valve stem seals and rings
if they are failed or the valve stems guides are worn then the vacuum sucks oil past the seals and down the valve stems into the combustion chambers , resulting in the smoke when the system again fires up on acceleration
find an accrdited service center with experience on the make of car, have them do a compression test (wet and dry) to determine engine condition and if the rings prove a good compression , then they will be able to change the valve stem seals with out removing he head/s
get quotes first

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1 Answer

How to replace the head gasket on an 86 FORD BRONCO


A torque wrench to tighten the bolts to spec. Necessary tools to remove the head bolts. A gasket scraper for the rocker cover gasket and the head gasket.. If you have a blown head gasket the chances of a warped head is about 98%, so be prepared to have the head machined flat before reinstalling the head. You might want to do a valve job and replace the valve stem seals since you're going to remove the head. If you decide to do a valve job, you MUST do both heads or the engine will never run good.

Aug 12, 2016 | 1986 Ford Bronco II

1 Answer

How to replace the head gasket on a 2004 Chevrolet Colorado


Your heads may not have to come off, you have worn valve stem oil seals, some mechanics have the gear to change your stem seals without removing your heads, this is a massive save in labour costs

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1 Answer

Dark water coming out tail pipe when I start my 1993 Saturn sl1


Oil in a cylinder is never good. There are several ways for the oil to get there and different prices to fix it.

Valve stem seals go directly around the valve and keep oil from the valve train from entering the combustion chamber. A worn or cracked seal can let oil run into the wrong place. Depending on how the camshaft and valve lifters are fitted, the valve stem is at the bottom of the camshaft and lifter. The overhead Cam models bury to valve stem deep inside the head.

Good practice would be to replace all seals at same time, but 1 cylinder could be done independently. But you are usually doing 90% of the work to do 1 set of seals. If a V-6 engine do the bad bank completely.

Head gasket, oil circulates through passages. Requires removal of everything above the head so gasket can be changed.

Bad Oil ring on Piston. Requires removal of head, oil pan, possibly motor to access crankshaft.

There are some tests which can help tell the difference between the problems. Some of it is visual so you need some disassembly for that. This is not going to be as simple as changing a waterpump or an Alternator. But the valve stem seals are reasonable and the head gasket is not so bad.

Can not say what labor will cost, but it will be probably 80% of the bill.

Oct 20, 2012 | 1993 Saturn SL1

1 Answer

Suspect valve stem seal caused smoking after being idle, replaced head gasket set and p'rings,t'belt, plugs, oil & air filter as there was no service history at 66,000 miles. fired up fine...


If it only smokes after you crank it up and then stops after it warms up usually that is the valve seals letting oil leak down in the cylinder after you cut it off .

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cylinder head gasket or a valve stuck slightly open you can get valve cleaning spray from halfords spray in to air intake while engine running should free valve otherwise head gasket renew

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Blowing black smoke on acceleration 2.5 exceed turbo intercooler I have a Mitsubishi 2.5 diesel with what sounds to be a similar problem except it happens when you rev the engine suddenly but stops...


1 Inspect Piston Ring Set Worn or broken piston rings. grey_line.gif 2 Inspect Valve Stem Seal Cracked or brittle valve stem seals allowing oil to enter combustion chamber. grey_line.gif 3 Inspect Head Gasket - Performance Head gasket leaking coolant into cylinders grey_line.gif 4 Inspect Fuel Injector Rich injector grey_line.gif 5 Inspect PCV Valve Plugged or damaged pcv valve. grey_line.gif 6 Inspect Engine Worn or scored cylinder block grey_line.gif 7 Inspect Piston Worn or damaged piston. grey_line.gif 8 Inspect Valve Guide Worn valve guides

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1993 TOYOTA TERCEL 1500cc Valve Seals Replaced now smokes much worse


You either have had the wrong valve seals installed, they are physically missing, or the valves are incorrect (too loose in the guides/stem too thin). The rocker arm seals will not contribute to your issue. If it did not have the oil smoke before you took the head off, the issue is with whatever the machine shop did. Valve seals have to fit TIGHT, or oil will go down the valve stem into the intake.
Take the head back to the machine shop & tell them to fix it. For free.

Aug 23, 2008 | 1993 Toyota Tercel

1 Answer

Celica ST 1.8 Valve stem seals


When does it smoke? All of the time, or just when you start it? If it smokes all of the time, consider piston rings. If you have lots of smoke when first starting only, valve seals and possibly worn valve guides are the culprit.

Jul 29, 2008 | 1998 Toyota Celica

1 Answer

My mx3 just had the head done and it is still blowing blue smoke once a day when i first start it... the mech that did the head said the compression was done and good and that when they opened the head...


Sounds like the excuse is a load of BS to me. If that was the case, the oil would of been burnt off during the normal test drive after they completed the head. I'm assuming you had a blown head gasket?

Blue smoke is indeed oil and if it ONLY occurs at start up then clears itself after some driving, it's the valve stem seals or valve guides (but more likely the stem seals).

They were most likely not replaced during the overhaul.

The stem seals stop oil from the upper lubrication in the head travelling down the valves into the combustion chamber and burning with the fuel.

While the engine is running, there is enough movement in the valvetrain (all the bits that move the valves) so that oil cant make it down into the combustion chamber.

However, when the engine is stopped and left for a period (ie: overnight) oil can trickle down into the combustion chamber through the seals which is why when you first start it up the next day it blows blue smoke. All that gathered oil in the combustion chamber is burning off.

The reason why they probably haven't changed the seals is simple: they make more money.

As a mechanic doing a head you have 2 options: You can either get what's called a 'Headset' which is the head gasket with all the other gaskets involved and stem seals OR you can buy the head gasket by itself and reuse the old gaskets and not replace the stem seals.

The head gasket by itself is half the price of the Headset but you can still charge the customer for the full headset....see where im going? Trust me, this kind of practise is unfortunately very common and one of the reasons I got out of the industry.

Once a car overheats due to a head gasket or any other problem, the stem seals nornally always have to be replaced because they harden due to the heat and lose their sealing power.

The solution? The head has to come off again to replace the seals and these guys probably know it so they are going into BS mode to protect themselves.

You have to insist they fix the problem because it wont go away and don't back down!

Oh, and for future reference there are only 3 kinds of smoke you can get:

Blue = Oil burning
White = Water burning (pretty normal in the morning)
Black = Fuel burning (Mixture running too rich)

Hope this helps :)

Jul 14, 2008 | 1994 Mazda MX-3

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