Mechanic says I have a burnt valve... is it even worth it to repair?

**FACT** · 05-16-2009 08:15 AM

Hey 'zine,

I've posted a few threads on here trying to figure out why my car is misfiring and running like complete shit right now, and after testing the ignition coil, the spark plug, and the fuel injector, I took it to a mechanic that I know and he says I have a burnt valve. He told me this would probably require a head teardown and rebuild and I'm wondering if this is even worth it. The rebuild would cost around 3000 dollars, and after all the other money I have had to spend on this car in repairs I think maybe I should just try and trade it in. What are your opinions on this matter before I let this thing go?

**lowandslow4now** · 05-16-2009 08:24 AM

have you done a compression test? If not then I would do one first to see if there are any internal issues.

**somebody5788** · 05-16-2009 09:07 AM

Originally Posted by lowandslow4now

have you done a compression test? If not then I would do one first to see if there are any internal issues.

That is fine for confirming the mechanics claim but wont prove much else. What engine do you have?

Edit: Nvm I looked at your previous posts. 01 1.8t

**Seerlah** · 05-16-2009 09:23 AM

$3,000 for a head rebuild is a jip (you can get a fully built 2.0 long block for $4,500 w/built AEB head:0 miles). I would rather try and source out a used head, rent an engine hoist, and replace the head myself (and I am a semi-noob

).

**FACT** · 05-16-2009 10:07 AM

Well given the premises that I: 1) do not want to rebuild anything myself. 2) believe what my mechanic says about the status of the engine

what should I do? Is an a4 with a burnt valve worth much of anything in a trade-in?

**djwimbo** · 05-16-2009 10:21 AM

Originally Posted by FACT

what should I do? Is an a4 with a burnt valve worth much of anything in a trade-in?

Not worth much at all, especially on trade in. You might get $2800 for it as a trade in, probably $3500 or a little more to a private party or enthusiast depending on other conditions.

I'd hook you up on dropping a head on if I still lived in OH. Unfortunately you're 3hrs away from "free labor" at the school I went to as well.

I'd agree though, $3K for rebuilding a head is too pricey. $3K for a head and engine rebuild is a decent price.

It all boils down to what it's worth to you. If you like the car and want to drive it for another 3years, $3K wouldn't be too bad of an investment. If you can't drop that kinda cash on it, bail while you're ahead and accept your losses.

**ghost6303** · 05-16-2009 11:42 AM

buy a working used head for $600 and pay the mechanic $1000 to install it. that would save you 50% right there. what exactly does burnt mean anyway? like melted? or did he mean bent?

**somebody5788** · 05-16-2009 12:54 PM

I have a head I'll inspect it to make sure its all good. I can probably have it gone through for less then 600.

**Don Supreme** · 05-16-2009 02:14 PM

Originally Posted by FACT

Well given the premises that I: 1) do not want to rebuild anything myself. 2) believe what my mechanic says about the status of the engine

what should I do? Is an a4 with a burnt valve worth much of anything in a trade-in?

Do you really trust this mechanic?

Burned valves on a 1.8t are not very common.

How did he come to this diagnosis.

**sean1.8t** · 05-16-2009 02:30 PM

Originally Posted by ghost6303

buy a working used head for $600 and pay the mechanic $1000 to install it. that would save you 50% right there. what exactly does burnt mean anyway? like melted? or did he mean bent?

"A "burned valve" is a valve that has overheated and lost its ability to hold a leak-free seal. Valve burning is usually limited to exhaust valves because they run much hotter than intake valves.

The diagnosis of a burned valve is usually the result of a compression test. If a cylinder shows little or no compression, it frequently means the exhaust valve is not sealing. The valve may or may not be actually burnt (melted), but have other physical damage such as cracks or areas where pieces of metal are missing or eroded away from the valve face.

The cure for this condition is to remove the cylinder head, replace the bad valve and reface (or replace) the valve seat. As a rule, the head is usually given a complete valve job at the same time because the rest of the valves and guides probably need attention, too. If one exhaust valve has failed, the rest are probably on the verge of failure if they haven't already started to leak.

Why Valves Burn
There are several reasons why valves burn. One is normal wear. As an engine accumulates miles, the constant pounding and thermal erosion wears away the metal on the face of the valve and seat. The exhaust valve sheds most of its heat through the seat, so when the face and seat become worn and the area of contact is reduced, the valve starts to run hot. Eventually the buildup of heat weakens the metal and pieces of it start to break or flake away. Once this happens, it forms a hot spot that accelerates the process all the more. The valve begins to leak and compression drops. The result is a weak or dead cylinder and a noticeable drop in engine power, smoothness and performance.

A bad exhaust valve will also increase exhaust emissions significantly because it allows unburned fuel to leak into the exhaust. High hydrocarbon (HC) emissions, therefore, may also be an indicator of a burned valve.

An exhaust valve can also burn if the valve lash closes up for some reason (improper lash adjustment, cam or lifter wear, a bent push rod, worn rocker arm or cam follower, etc.). The lack of lash (clearance) in the valvetrain prevents the valve from closing fully, which causes it to leak compression and overheat.

Valve burning can also be caused by any condition that makes the engine run hot or elevates combustion temperatures. This includes cooling problems, abnormal combustion like detonation or preignition, loss of exhaust gas recirculation (EGR), retarded ignition timing or lean fuel mixtures."

**sean1.8t** · 05-16-2009 02:34 PM

Originally Posted by Don Supreme

Do you really trust this mechanic?

Burned valves on a 1.8t are not very common.

How did you come to this conclusion?

x2. with shitty sodium filled exhaust valves on the 1.8t. you're much more likely to drop a valve than to burn one.

OP, do you have any mechanical skills? or does anyone you know? and do you have any tools available to you?

a head swap is by no means as easy as rotating the tires, but with the DIY and a Bentley manual(optional really) it's not too bad. you could have the valve(or all the exhaust valves) and guide replaced by a machine shop, and swap it yourself for $1000-1500 depending on what you do. or you could buy a used head and save even more money than that.

**FACT** · 05-16-2009 05:18 PM

The car had been running like crap ever since the first head replacement I had to do (covered under warranty, broken timing belt, shop's fault), and I eventually got it checked out and it came back as a cyl. misfire in #2. Over the course of several months I replaced the sparks, the coil, and swapped the injector and was still getting a misfire. The shop that originally rebuilt my head is out of business now and this is therefore going to have to come out of my pocket even though it is not my fault. The mechanic that diagnosed my car is a friend and seems to know what he is doing, although with my experience with this car nobody really seems to know what the hell is wrong with any 1.8t lol. I really have no choice but to take his word on it.

**somebody5788** · 05-16-2009 05:33 PM

Originally Posted by FACT

The car had been running like crap ever since the first head replacement I had to do (covered under warranty, broken timing belt, shop's fault), and I eventually got it checked out and it came back as a cyl. misfire in #2. Over the course of several months I replaced the sparks, the coil, and swapped the injector and was still getting a misfire. The shop that originally rebuilt my head is out of business now and this is therefore going to have to come out of my pocket even though it is not my fault. The mechanic that diagnosed my car is a friend and seems to know what he is doing, although with my experience with this car nobody really seems to know what the hell is wrong with any 1.8t lol. I really have no choice but to take his word on it.

Well if it is worth the trip to you our shop could definitely get it figured out for you. And if it's the head we can either send yours out to get rebuilt and a new headgasket job or if your head is no good I have one sitting around and one way or another I guarantee you your car will be done correct. We stand behind our work. Has anyone checked the timing? Your timing belt could be off by a tooth.

**onemoremile** · 05-16-2009 06:00 PM

It should be diagnosed with a leakdown test. That will tell you if you have leaking valves. A leaking valve will not cause misfires. It would cause a slight loss in power from that cylinder but usually not enough to really worry about.

Get a second opinion. 3 grand is more than worth knowing for sure.

A head can be pulled easily at home. Disconnect everything and unbolt the turbo, pull the valve cover, pull the head. It is incredibly simple work.