'98 K1500 overheat and power loss

First of all, I’m new to this forum and am very impressed with the level of activity and responses. I'm writing because I need some diagnostic help with an overheating and power loss problem with my '98 K1500 (120k mi). Here is the sequence of events/symptoms:


- The truck overheated (gauge temp reached 260) within about 1 mile of my house.
- Temp dropped to 220 as I reached my house, where I found very little coolant in the system.
- Found a leak in the water pump so I replace it along with hoses, cap, and thermostat.
- Took the truck for a test drive (~10 mi) where it began to idle rough at stop lights.
- Pulled into a parking lot and soon lost all compression (NO power at any RPM).
- Temp began to spike again (up to ~240)
- Never any white smoke from the exhaust.
- No power brakes (I assumed this was from a loss of manifold vacuum).
- At idle, the air intake was whistling from air blowing OUT through the MAF sensor.
- Some water dripped from the air intake when I removed the K&N filter.
- Towed the truck home and did a cooling system pressure test.
- The system held no pressure, and the air I pumped into the radiator inflated a baggie I had placed over the MAF intake.
- The oil had the telltale milkshake consistency, and there were orange deposits on the oil filler cap.
- Regretably, I didn't do a compression test because I lent out my guage.

I assumed I had the infamous intake manifold gasket failure, and began the job of replacing it with the redesigned Fel-Pro set. The passenger side gasket was trashed, but now (in mid-assembly) I'm wishing I had checked head gaskets. I know they almost never fail on this engine, but I also know that overheating is the exception to this rule. My question is, would a severely blown manifold gasket cause the complete lack of power I experienced? I'm going to get my compression tester back and test the compression as soon as I get the distributor back in, but I'm starting to second guess my diagnosis. Any insight would be appreciated. Sorry for the long post, but I hate it when people don't give enough info.

The blown intake gasket was probably just the start of the problem.
You must take into consideration that the eng. got hotter than the guage said because the cooling system wasn't full.
A compression and leakdown test needs to be performed.

Good luck
Marc

You might have even cracked the heads.

Thanks guys. You're confirming what the burning in my stomach has been trying to tell me.

Most blown intake gaskets show signs of external coolant leakage. The coolant and intake passages are not really that close together. But it could happen!! I'm thinking more along the line of head gasket. If you do pull the heads, definately have them checked for cracks due to the overheat.

Along with the leak-down and compression test, look at the spark plugs out of each cylinder. They will tell you more of what's happening in each hole.

Keep us posted as to what you find out................Steve

Good news... I think.

Got everything back together yesterday. I pressure tested the cooling system and saw no leakage. Started the truck with the gauge on the radiator and saw no pressure build until the coolant heated up. Test drive went quite well too. Temp gauge stayed well below the 210 mark, and I've got full power and a good clean idle. No oil in the water and no water in the oil (flushed oil once and refilled), and I'm not loosing any coolant.

Did I dodge a bullet here, or would you guys still do a leakdown test?

Thanks again for all your help! I've got a few other small issues that I would like your input on, so I'll be back soon.

-Chuck

If it is running well just drive it. Sounds like no major problems. Just watch your oil and coolent.

400 miles (travelled this weekend), and still running well with no leaks.

Thanks again,
Chuck

Chuck: You really didn't say what things you replaced to fix your problem. Can you give us all an update on that?

Thanks.

Absolutely, sorry about that. I guess I was a bit vague about the repair.:rolleyes: Here are the details:

- As mentioned earlier, I initially replaced most components in the cooling system (water pump, rad cap, thermostat, hoses).
- Then, after recognizing the internal problem, I removed everything down to, and including, the lower intake manifold (and the pass. side valve cover as recommended here).
- The significant carbon deposits were removed from the intake manifold.
- All gaskets were replace with the beefy Fel Pro gasket set (part #MS98000 T) that everyone's been raving about.
- I also replaced the distributor cap and rotor while I had them off (~50,000 miles since last changed).
- The oil was flushed twice, and I will change it one last time after 1,000 mi before returning to a normal schedule.

Looks like a short list after all the late nights spent in the garage. Most of the time was spent cleaning. I really like the FelPro gasket set. As I said before, the factory gasket was absolutely shredded. Please let me know if anyone would like more detail on any step. This repair is so well documented on this and other sites that I had a high level of confidence going into the job.

Thanks,
Chuck