99 4.3 Vortec

Took my GMC Jimmy in for a no heat problem and was informed that is was the intake leaking. This is the second Jimmy I have owned so I was not surprised at this. The problem is that once everything was put back together and the mechanic started motor it had a bad knock to it. They disassembled everything including removing the head on the on the right side of the motor. In cylinder #6 they found a small piece of metal about 1/8" x 1/8" x 3/4" long. The only thing they can think of is when they pulled the intake it fell into the head and pass the valves when the motor was turned over. It appeared to have caused no damage and put it back together. I still have a knock, they have repleased the lifters and last Friday they replaced the rockers. Still knocks. Anyone have any ideas?

First thing I'd do is find another mechanic that's not going to drop stuff in to your cylinders...

Second, no heat is not because of a intake leaking, it is because of:

A) Thermostat is stuck open. Usually can be seen as the gauge only barely going over the 1/4 mark on the dash gauge.

B) Your heater core is plugged and you need to get it flushed. Best to flush the whole cooling system if you need to do this and replace the coolant.

Also, replace the rad cap with anything other than an AC Delco.

Second, no heat is not because of a intake leaking, it is because of:

A) Thermostat is stuck open. Usually can be seen as the gauge only barely going over the 1/4 mark on the dash gauge.

B) Your heater core is plugged and you need to get it flushed. Best to flush the whole cooling system if you need to do this and replace the coolant.

Also, replace the rad cap with anything other than an AC Delco.

Thermostat was replaced, coolant system was flushed out twice and radiator cap was replaced. Blew heat while driving down the highway, would starting blowing cold and temperature gauge would climb at slow speeds. Coolant system would not hold pressure and was leaking on the back side of the intake. The 4.3 are known for intake leaks.

Odd, I wouldn't say "known" for the problem because you are the first to note it.

But thanks for the info, I will remember it for next time.

Odd, I wouldn't say "known" for the problem because you are the first to note it.

But thanks for the info, I will remember it for next time.

I had a 96 Jimmy before this one. When I went to trade it in, that is one of the thing they looked for, to see if the the intake was leaking or was repaired. When I bought this one I was very much aware of the coolant problems with the DEXCOOL, ball joints, idler & pitman arm & wheel bearings. All have been replaced.

Are you aware of any problems with the lifts in the 4.3? In the 96 I had a little piston slap but no other problems. I have been going to the same mechanic for the last 11 years. Very good repetation. The piece of metal is just one of those things, you take every precaution but sometimes things happen. He has not charged me a dime for all the work & parts he has installed trying to find out what making this noise. It really sounds like valve train. They are replacing all the lifters today as recommended by General Motors.

We will see what happens tomarrow.

No piston slap on a 4.3L.

Start using a proper oil filter and 5w30 oil for proper lubrication.

Don't use a fram oil filter.

No piston slap on a 4.3L.

Start using a proper oil filter and 5w30 oil for proper lubrication.

Don't use a fram oil filter.


Use only AC Delco & Valvoline 5w-30. Change oil every 2-3000 miles.

i live in alaska and even in the summer my temp hasnt gone above the 1/4mark on the thermostat. seeing as the weather's trying to be winter
(and it's cold as :eek2: ), should i get it replaced?

Yip, your temp is too low and your stat is stuck partially open.

Better yet, best to get your cooling system flushed and filled.

Use only AC Delco & Valvoline 5w-30. Change oil every 2-3000 miles.

That is odd.

Maybe you should do a flush if you are getting startup lifter clatter.

how much would a thermostat be in $US? and is the process complex at all? read back into a previous post, & chembrad said it didnt take him more than half an hour if he took his time. as a n00b, should i give myself about that long?

Go check the prices out for yourself, we can't quote you the price seeing it is different in every area.

If you use the repair manual and take your time, it shouldn't take more than an hour tops.

You will need the new stat and the thermostat housing gasket.