23rd Mar 2009, 10:55


I have had my 1999 GMC Jimmy 4x4 for about 5 years and have had many problems with it. New transmission, alternator, battery, leaking rear-end differential, front right wheel hub assembly, front brake rotors, rear inoperative wiper, busted seat recliner handles... - some of these are normal maintenance. BUT, my latest problem - anti freeze in the oil. I suspected for the last couple years that's where it was going, at a very slow pace, because it sure didn't leak on the ground anywhere. Finally 2 weeks ago it progressed very rapidly, I could not keep the radiator full and it was not leaking on the ground. Thought it may be a blown head gasket and quite a few others I talked to agreed it may be. Come to find out after tearing the engine apart myself (which was a total nightmare), that it was not the head gasket (s), it was the intake manifold gasket. Soooo, approximately $600.00 later after getting it all put back together - guess what? It still doesn't run (but it did for a few) : (.

When it first died, when I was dumping anti freeze in faster that I could blink an eye for a couple days, the motor finally said I am not going to work at all anymore. I lost all power... and it quit running all together. We pulled it home, put it in the garage...

Thinking I would replace the bad gaskets (intake and heads), along with plugs/wires/cap/rotor/broken fan/water pump (why not right?), I would have the problem resolved. Well. It started okay, kind of, let it warm up, then took it for a test drive. It ran so, so - not much power..., 8 blocks from home I lost all motor power again and the motor was making squeaking sounds right before it quit.

Bad oil pump now? Plugged oil returns in the block...? Who knows. The motor now seems like it is siezed now and will not even turn over - with a fully charged battery. It did act similarly the first time it took a crap on me before tearing it all apart...

Oh, initally before the tear down of the motor I drained over 4 gallons of crap out of the crank case - the first gallon being straight bright green anti freeze, the remaining 3+ gallons was thicker than a chocolate shake and looks just like one (draining very very slowly).

Now what? Taking a day or two off then I'll try to get some oil dumped on top of the heads, via the valve cover bolt holes, let it seep down in the motor. Then I guess I'll try to hand crank the motor over a little to see if it is seized. If its not, I'll change the oil filter (which I forgot to do previously - DUH!!!), maybe it's plugged up w/chocolate milk shake? Then I'll try starting it again. Maybe I have to drop the oil pan and check the oil pump? (is that what caused the motor to squeak? no oil?) - is the pump all plugged up.

WOW!!! Totally fun stuff... And the motor ran perfect right before the oil started getting contaminated with all the anti freeze.

Did the blown intake manifold gasket cause another problem? Or did another problem cause the bad intake manifold gasket?


22nd Apr 2009, 09:24

Security light on while running.

24th Aug 2009, 13:15

I have had my '99 GMC Jimmy for a little over 4 years. Has been a great vehicle. Like everyone else has mentioned I have had these problems:

- Front wheel bearings

- Lower ball joints (they are notorious for going thru these)

- 4wd won't work, replaced the 4wd actuator but something is not engaging. Might be a hose.

- Key stuck. I replaced the ignition switch wiring but still no luck. I am taking it to the shop tomorrow.

- A rattling in my front passenger side suspension. Cannot figure that out.

So I guess the question is, are you willing to deal with these problems (replacing ball joints, wheel bearings, key stuck in ignition, and questionable 4wd)? Every vehicle has its issues, and especially one that is 10 years old.

5th Sep 2009, 07:27

1997 GMC Jimmy 4wd 4dr 4.3 litre.

Will not start in high humidity, or early morning dew, but will start when the early morning dew is gone and run absolutely perfect.

Installed new ignition coil, and test next morning.

Installed new distributor cap and rotor, and test next morning.

Cleaned out breather holes on bottom of distributor to stop potential condensation and test next morning.

Drilled 4 small 1/8 holes at bottom of distributor cap to stop potential condensation and test next morning.

Installed ground strap from engine block to battery and test next morning.

Ignition switch failed on side of highway, so I installed a separate ignition switch in the dash to bypass the faulty ignition switch that was designed to fail when the warranty is up by some moronic engineer.

Installed additional relay to bypass the 2 second PCM control of the fuel pump during start-up. This allows me to directly power the fuel pump. And test the next morning.

Change fuel filter verify proper fuel pressure and test the next morning.

Change throttle position sensor and test the next morning.

Change the idle air control valve and test the next morning.

Bypass the oil pressure/fuel cutoff switch and test the next morning.

Change the manifold absolute pressure sensor and test the next morning.

Borrow power control computer from friends Jimmy, engine starts the next morning Hmmmmm.

Disassemble my computer, and discover that the same moronic engineer has internally used the aluminum body case as a ground point on several places to the copper printed circuit board and connectors.

This has caused galvanic corrosion because of electrical current flow between two dissimilar metals.

Any electrical engineer or electrical/electronics person knows that you cannot mix copper and aluminum when making connections for this very reason.

I cleaned up the corrosion, repaired the copper circuit board where the connections are and reinstalled the computer.

Tested the next morning and it starts fine and runs well.

This is my second GMC vehicle and my last.

My first had a leaky intake manifold gasket at 4,000 miles, then a broken intake bolt and another leak two weeks later. GM claimed it was caused by over torque when the dealer had to change the faulty intake gasket. They told me to pick a fight with the dealer. The dealer told me it was the original stressed bolt that caused the intake gasket to fail in the first place, and GM should cover both repairs under warranty.

15th Sep 2009, 12:53

I have a 1999 Jimmy. I changed the front brake pads, rotors and calipers. Now I can't seem to get the brakes to bleed. Any ideas?

4th Oct 2010, 22:26

I have a 1999 SLE Jimmy with a 4.3 engine. I think it is an SLE, the decal went soon after I bought it.

It won't start now, but to reflect back, it wouldn't start at all when the temperature dropped below freezing. The battery was dead. It was replaced with a new battery, the same thing - dead battery in the morning. So I did some checks with my trusty Fluke meter. It turns out there is a current drain in the colder temperatures with nothing on. Checked all the known circuits, after checking no lights were on, by removing one fuse at a time. No luck. When the battery is first connected I heard several clicks from the computer. Hmmm. Is it rebooting? I checked the current flow after the battery is connected for five minutes. There is still an amp current drain with nothing on. It takes 45 seconds to disconnect the cable off the battery. That fixed that problem and a new charged battery is good for at least 3 hours with a 3 amp drain. But now the heat is on full all the time.

I checked the fluid levels, the anti freeze is low. I filled it up then next day it was low again. There are no sighs of leaks and no anti freeze in the crankcase. Well, buy a new used car? I'm retired, no money to waste on lemons.

Jimmy sat for 5 months and tried to start it today, it rolled over reluctantly with a new battery, but only fired once. It sounds like it fired. I'll try again tomorrow after putting an additive in the tank.

4 Oct 2010.