1999 grand cherokee 4.7 engine

[arnea]

I have a 1999 jeep geand cherokee with the 4.7 engine with 176,000 miles on it. It runs great but puffs blue smoke at a traffic light. Obviously it could be valve seals. Question...are the valve guides known to wear on this motor or is it usually the seals??Also, I notice sometimes the oil pressure goes real low at idle but goes up to 40 lbs when I start driving..I have changed out the oil sending switch. Thanks Arne

[Bob D.]

Sounds like the motor is getting a little loose.
The only way you can get an idea if it's the valve guides or rings is to check the exhaust right after start up after it has been sitting overnight - if it puffs blue smoke it is probably more valve guides, if it's about the same as when driving it's probably rings.
Either way, if you are seeing blue smoke at idle that's pretty excessive - my vote would be badly worn rings.
I've never heard anything about valve guides being a weak point on the 4.7 engine.

[arnea]

It only puffs blue smoke from a standing stop. Once its going I do not see any visible smoke. If its only seals I can do that without taking the heads off. Arne

[wafrederick]

The valve seats are very weak,come out of the head and the cylinder head is junk right away.I have seen this happen.A reman 4.7 is not cheap,a reman 4.7 from Jasper is $5,000.00 and the Chrysler reman is more.One other differance is the warranty,Jasper has a 3 year 100,000 mile warranty and the Chrysler reman has a 3 year 80,000 mile warranty.

[xj31]

Originally Posted by wafrederick

The valve seats are very weak,come out of the head and the cylinder head is junk right away.I have seen this happen.A reman 4.7 is not cheap,a reman 4.7 from Jasper is $5,000.00 and the Chrysler reman is more.One other differance is the warranty,Jasper has a 3 year 100,000 mile warranty and the Chrysler reman has a 3 year 80,000 mile warranty.

For your FYI,Mopar reman is now 3 year 100,000 miles warranty.I believe that went into effect in March of this year.

[wj_ens]

Hello, I have the same problem, same car, a little less milage though (150k+).

Sometimes puff at stoplights, very few times at start up, sometimes when using Chevron oil it drinks the oil (consumes it) over 3500 miles period.. Oil Gage never goes down. Started using the Quaker State SUV High Mileage Oil and when changing the oil after 3500 miles is ok but still sometimes puff.

Any ideas on what the problem could be? Arnea, did you fix yours?

Thanks,
Puffing WJ in Baja, Mexico