little-red

Howdy guys. First off, many thanks -- I've been a long-time lurker and have learned a lot, first time poster.

"Little Red" is having an issue -- she's a 94 X-cab pickup, V6 3VZE, SAS, running 35s. Usually a pretty reliable rig, but over the past year she stumbles as I accelerate. Even in neutral, if I hit the gas hard, the engine misses (never backfires) for a second before it starts to rev.

I did the whole head gasket replacement and top-end overhaul dance almost 10 years ago (also a new MAF then), so I figured it was time for a serious going-over again. Perhaps that would fix the stumble. So this time I replaced:
- timing belt kit
- water pump / thermostat
- belts
- rotor / dist cap /plugs / wires
- removed and cleaned oil cooler and oil pan
- new pulley bearings, PS pump rebuild, PS hoses, ...

After all this, the stumble is unchanged. (Checked EGR: modulator seems ok, EGR kills the engine if I suck on the hose; Haven't yet checked the TPS because it seems I need to take the throttle body off to see what I'm doing.)

Bugger.

But to make matters worse, now it's overheating. I can run it and get it up to operating temp. Upper radiator hose seems to have no flow, although the radiator does get hot and eventually the system pressurizes. Heat in cab is blowing cold. If I drive it around the block, it boils over.

If the thermostat were bad, wouldn't the cab at least blow warm? So I'm thinking the pump isn't pumping. But that is such simple tech -- how could it not pump? The timing belt isn't slipping across its pulley. I've run and topped up the coolant a few times, so not thinking it's low or got a bubble.

Someone please tell me where I'm stupid!

-chuck

ksti

So you burped the cooling system and it's still overheating?

little-red

Yeah - but only by getting it hot, squeezing the hoses to slosh the coolant, topping it up, and repeat.

That's worked for me many times before, but I see other people do this on a slope.

Queuing up the slope trick as the next thing to try...

rworegon

HG failing again? Stumbles and overheating.......hmmm.

TNRabbit

Have you pulled diagnostic codes?

little-red

Good question. I've drained off some coolant and pulled the dipstick, so far I don't see mixing.

little-red

I had the battery unhooked while I checked the resistance on the coil and ignitor (both checked out ok). Stupidly only checked codes afterwards... clear.

Then I force-fed the upper radiator hose (tilted it up, poured coolant in, and covered the end with one hand while squeezing with the other). Got a bit more in that way, and now the electric fan is cycling, and cab is blowing warm air.

So that might be progress, but I thought I was at this point (NOT overheating) on the first test drive after the tune-up. (Overheating has been intermittent after that tune-up.) So will do another test drive and see what's what....

Thanks all.

TNRabbit

Might be your fan clutch, also.

TNRabbit

Or, check this:

little-red

After forcing more water and antifreeze in last weekend, I took the truck for a 50+ minute drive today to pick up some shelves for the wife (late xmas present). It did great!

Here's what I think happened -- after the tune-up, I did a good flush of the cooling system with plain water, because it's been 2 years. I then drained off some water, mixed in some coolant (not enough), and apparently introduced a bubble, so part of the system was pure water. Got distracted on other projects and didn't think further about it.

Then I did various short trips, and the temps dropped to sub-zero. The coolant re-mixed, and got further diluted, and somewhat froze. That's why I the heater blew cold, and the pump didn't seem to pump -- ice!

So after after having a heater on it all day last weekend, and re-burping, and re-mixing the antifreeze, it's doing great. The biggest surprise is that I don't think I cracked anything...


Lessons --
1. Even if it seems burped, it might not be.
2. Don't get distracted from a project until you know it's completed right!

Thanks for the help!

(There's still the stumble when hitting the gas, but that's another post another day after I can do more troubleshooting....)