removed head have valve question

[xirdneh]

My friends Tercel was steaming out the exhaust and had water in oil (brownish oil). We did a compression check before pulling head. #1 @ 180 , #2 @ 175 , #3 @ 90 , # 4 @ 180.
After head was removed the top of the #2 piston was clean and the others were black so I'm guessing it was getting some water. The #3 exhaust valve was biege colored while all the other valves were black. I pulled the valve and it was not burned but it was somewhat pitted as was the valve seat. I am wondering what it is trying to tell me?

[sdoan]

A tan exhaust valve is normal in my experience because they run so hot. The pitting is not good, is this the only pitted one? Are all the other valves not pitted? If so, perhaps an intake leak at the intake manifold gasket. Also check that the vacuum fittings are tight - the fitting for the vacuum brake booster is on the #3 or #4 intake runner.

BTW Is water in the oil due to head gasket failure? I've had a cheap Chinese head gasket fail under a resurfaced head. the Felpro version worked great.

A valve grind and new head gasket set sound like the thing that's needed. (Unless the engine has frozen or overheated badly.)

[takza]

The coolant pulled into the cylinder steam cleans it. My guess...new exhaust valves...have the head tested for cracks...surface defects...regrind...valve seals...new good gasket...FLUSH that oil.....

[4wdchico]

A tan ex valve is more normal than a black one. How many miles on this engine? High mileage engines develop greater valve to seat contact area and this results in more heat transferring to the seat from the valve. This can result in an exhaust valve not running hot enough to burn off the carbon & this is likely why you have three black valves. The guess on the brake booster line on the intake runner to cyl #3 is a good one, I have seen those fittings get loose in the intake runner on the t4wd. Another good guess is that your low comp on cyl #3 was caused by a tight ex valve and it had just not gotten to the point of burning yet. If you had done a wet comp test along with the dry one we would have a bit more to go on here.

I second the all new ex valves at a minimum when you get the head done.

[xirdneh]

A tan ex valve is more normal than a black one. How many miles on this engine? High mileage engines develop greater valve to seat contact area and this results in more heat transferring to the seat from the valve. This can result in an exhaust valve not running hot enough to burn off the carbon & this is likely why you have three black valves. The guess on the brake booster line on the intake runner to cyl #3 is a good one, I have seen those fittings get loose in the intake runner on the t4wd. Another good guess is that your low comp on cyl #3 was caused by a tight ex valve and it had just not gotten to the point of burning yet. If you had done a wet comp test along with the dry one we wold have a bit more to go on here.

We do not know how many miles are on the engine it was a crate engine supposedly with low miles that the previous owner installed and we do not know how many miles he put on after that. I removed all of the valves to compare them. The black exhaust valves looked pretty good after wire brushing. Their valve seats are mildly pitted. The tan exh valve does not look that bad after wire brushing. It's valve seat is a little more than mildly pitted. When I removed the brake booster fitting and hose I did not notice anything unusual but I will inspect the hose all the way back to the booster when I get back to the car. I wish I had squirted some oil in number 3 cylinder and re-did compression test before we took it apart. Also wish I had checked the valve/rocker gaps.

[Petros]

I have found that pitting of the exhaust valves is pretty normal on high mile engines. I would replace the exhaust valves too, they are cheap and not worth the risk. I have burned mine, and have seen other Tercel engines melt the stem and drop the valve head into the chamber (trashing the engine). Setting the timing at 10-12 deg BTDC should prevent valve burning.

A vac leak, or a faulty carb, could cause the rich/lean variation in the combustion chambers.