motobehrens

Hello all,

I've always been able to find the info I've needed using the search feature, but not this time, and I'm hoping someone can offer their tech expertise.

A year and a half ago my '93 3.0 blew a head gasket at 190,000 miles. Not knowing any better, I had the motor rebuilt by a local(phoenix,AZ) engine rebuilding shop that had a 5yr/100k warranty. The shop was horrible to deal with, telling me to "quit #@%ing calling, it'll be done when it's done" as I made my once a week call over the course of 2 months. The engine always ran rough at idle after the rebuild. 12,000 miles later I take the truck to a local Toyota specialist(Toyota certified, with his own shop), for electrical issues, and he tells me the truck is running on 5 cylinders. Further testing proves it to be a burnt exhaust valve.

I return the truck to the engine rebuilding shop and tell them what is going on, hoping their 100k warranty will cover the problem. Two weeks later I get a call, "you had a vacuum leak in the line going to your PCV, we ain't going to warranty nothin". I said "BS, a vacuum leak doesn't burn valves, we'll take care of this in small claims." In response to the BBB, his excuse was that cold air entered through the vacuum leak and burnt my exhaust valve. He came up with that conclusion since there was a newer hose on the pcv to intake manifold,which meant there was a vacuum leak at one time and the hose was replaced. In actuality, there were no significant vacuum leaks and I had replaced the hose with an oem part vs off the shelf tubing which was kinked.

I then get the heads rebuilt and installed by the toyota mechanic who diagnosed the problem. He said the hack-job shop that rebuilt it probably did not reshim any of the valves after machining, and only put in what was originally there. The machine shop used by the toyota specialist noted that the "valve adjustment was zero on some, and others were not right. Head surface was rough." Actual exhaust valve measurements were <.002, .005, .008, .005, .007, <.002. With the correctly rebuilt heads, the truck runs great, and I drive it a couple days a week.

Anyway, I personally have never heard of a vacuum leak causing any more than a rough idle or maybe rich/lean condition, but I'm not a great mechanic. I was hoping someone could help me with the following questions:

1. Have you ever heard of anyone saying a vacuum leak could cause a burnt valve?

2. On the 3.0, if the valves are correctly adjusted, what else could cause a burnt valve?

3. What book, or maybe textbook would I find detailed descriptions of the causes of burnt valves, and the results of vacuum leaks, in order to disprove the hack jobs reasoning for not warrantying my engine? I couldn't really find anything useful in the Library.

4. On a rebuilt head, how quickly could the exhaust valves lose their adjustment, going from in-spec to .000?

Thanks a bunch for your input, this site is great and I've been coming here for several years for info.

Chris

toyaholic

vacum leaks will not burn valves up. a lean fuel condition can. sounds like a real crap job.

yota_krazy

x2. If you have a large vacuum leak then that would cause a lean condition which would burn a valve. But it sounds like the morons that rebuilt your motor probably adjusted a valve too tight and it hanged open a little too long at the wrong time and burned it. Thumbs down to hackjobs

jct61765

Whats the name of the shop that screwed you over? Let us know.

dwh91102

The #6 valve is known to burn, because of the poor design of the crossover pipe on the exhaust system of the 3.0. I have to call bs on the vacum leak, if there was that serious of a leak to cause that severe of a lean condition, you would have noticed long before you burnt a valve.

motobehrens

The number 1 cylinder was the one with the burnt exhaust valve, and the 35lbs of compression. Number 6 exhaust valve was at 0, or at least < .002, but still had good compression. The hack job shop that did the work was Number One Engine in Phoenix. They advertise in the back of the Truck Trader. The shop that fixed their mistakes was Toy Specialist in Mesa, AZ, with Baileys machine shop doing the machine work on the head.

junkyardblacksmith

Thats pretty sad. I know highschool and backyard mechanics that are more reliable than that.