Jeep Grand Cherokee (1997 V8 Laredo). Is my leaking timing cover gasket causing these codes?

Question

During the past year, my check engine light would come on but go off before I got time to pull the codes. About 2 months ago I started smelling coolant after long drives, but couldn't detect a level drop (dripping?) and the check engine light stayed. Recently it overheated - I pulled over and let it cool down before driving it about a mile to get home.
Here's what I found:
After running with a brick holding the throttle at 2,000+/-RPM for about 10 minutes it overheated. There was steam coming out of the engine area. After removing the altenator and running it I found that a small spray of coolant came through the timing cover gasket (only when the engine is really hot or overheated). I have concluded that when the engine gets hot the coolant starts to boil (and thus overheat) because it is no longer pressurized.
Replacing the timing cover is reasonable (under $300), but I want to be fairly sure that this is really the problem.
The codes are 12, 47, 21, and 55.

The codes come from turning the ignition on and off repeatedly. They then display on the odometer. This is exactly how they were listed on the odometer - I also expected the P-prefix based on what I have read.

I changed the oil about 750 miles ago and it is still full and brown, which I had interpreted as an indication that the head gasket is okay.

Also, the engine warmed up normally (climbing slowly) until the steam came out. Once steam came out, the engine jumped from around 210 to overheat in a matter of seconds.

I have cracked an engine block before (in a 72 chev), but this engine actually runs very smoothlym quietly, and cleanly and has no problem idling on its own.

Thanks for your help, I help these clarifications prompt more inspiration.

Answer 1

Fix what you know is wrong first, then worry about everything else.

Answer 2

In the first place at the first sign of overheating the "Thermostat" should be the first thing checked. It is a relatively easy replacement and only cost a few dollars.
The fault codes usually start with a "P" For example: The code: P1595 would be in the Speed Control Solenoid Circuits.

In the factory manual, there is another listing, but without the code designation, who can be sure. Here they are. (12: Evaporative Surge Solenoid circuit.) 47 is not listed in the factory manual (21 indicates that the Thermostat is not closing and the engine stays cold too long)
55 per se is not listed. Those number are not fault codes, I do not know what type of code reader you are using, but something else is bothering me.
You say that steam is coming out of your timing cover, but the only thing that should come out of that cover assuming a faulty gasket, is oil.

If you have water steam coming out from the timing cover, you may have cracked your engine block, in which case you have a real problem.

As I see it, you could have had a bad Thermostat, which caused your overheating It may have had nothing to do with the Check Engine Light.

The most common cause of an intermittent Check Engine light is the Speed Switch. It is a real weak element in these modern cars. They are attached to the transmission and do not have good heat resistance. The wire separates form the coil on the inside and it is Kaput.

You need to get a real accurate code reading as I have illustrated, that will tell you why the light is on. You may write to me when you get a proper "P" code and I would be glad to look it up for you.
I also have a book of generic codes as follows: (12) Camshaft position indicates
retarded, (bank 1.) valve timing. Could be caused by a worn timing chain and/or belt whichever the case may be. (47) is not listed. (21) Camshaft position timing advanced (bank 2)
(55) is not listed. Hope this helps.

Answer 3

I have a 2001 Jeep Grand Cherokee; however it is a 6 cylinder. I get about 19-21 in the city and 24-26 on the highway. I would imagine a V8 would get a little less than what I experience. I love my Grand Cherokee. It has been fun to drive and very reliable. If you are getting a good deal, I would say, "Go for it!"

Answer 4

WOW, that one is rather unusual. I am really shooting in the dark on this one, so be wary of my theory. Based upon some other engines that I have seen develop "weird failures" ( including one of the trucks where I work), it sounds to me like you may have blown an engine head gasket. IF that is the case, again this is only a theory, having it replaced will be rather expensive. As far as those engine codes are concerned, they may or may not be related. There is no way of knowing off hand.

Answer 5

Generaly an mil will not illuminate from fluid leaks.Depending on the operating systems used an mil will illuminate for faults in sensors or actuators such as an IAC.Can u get the deffinitions of these codes?I dont have the resourses to get them.Email me back if you can get them.

Answer 6

Thermostat needs repalced if coolant wasn't low when you did your test with the brick on the accelerator.