Engine overheating at idle - trying to diagnose

[DoctorRoboto]

Okay, more updates. The engine compression certainly doesn't indicate a blown gasket, but there's one cylinder that's a bit low (120, compared to others at 150-170). I can live with that, I think.

Will be flushing the heater core tomorrow morning, followed by a 10 minute coolant flush, then an extended rinse from the tee, and then top off with fresh fluid. What came out was pretty murky this afternoon, but nowhere near as bad as what was in the reservoir.

Spark plugs look like they've never been changed before, BTW. Swapping those out should make a world of difference.

 

[RonD]

What did the spark plug in the 120psi cylinder look like?

Very clean older spark plug indicates "steam cleaning", an indication of "water" getting into the cylinder.

But 120 is quite low for a small head gasket leak, with 160 average I would expect 135-140.

120 most likely means exhaust valve seat is burned so not sealing completely.

 

[DoctorRoboto]

The PO didn't leave me any mysteries - plug was covered in grime and oil on the threads. The tip was worn down to almost nothing, as were the other 5.

I'll run it for a bit and might check that one again after a long drive. Perhaps we just needed to let it turn over a bit longer, but we gave it a full 10 turns to come up.

Also, we did these with the engine cool - was this supposed to be with the engine warmed up?

 

[Tedybear]

The PO didn't leave me any mysteries - plug was covered in grime and oil on the threads. The tip was worn down to almost nothing, as were the other 5.

I'll run it for a bit and might check that one again after a long drive. Perhaps we just needed to let it turn over a bit longer, but we gave it a full 10 turns to come up.

Also, we did these with the engine cool - was this supposed to be with the engine warmed up?

It really shouldn't matter a lot about cold vs warm for a compression test. It's all about the numbers and the relationship with each other. If being 'warm' meant each number would be about 20PSI higher? Then the low cylinder would still be 120+20PSI.=140. And your other higher ones would be 20PSI higher across the board.

So it's going to be the relationship that needs to be examined.

S-

 

[DoctorRoboto]

Okay, I flushed the coolant system and put in new stuff. On this engine, it says the capacity is 11.8 quarts. I was only able to get about 7 quarts in there (firs 4 of coolant concentrate, then 3 quarts distilled) and then I had to put the rest of that gallon of distilled water in the reservoir. I didn't put in another 3.8 quarts of premix, which I have ready to go. Should I just put it in the reservoir, or wait and see if the radiator level gets lower at some point?

Also, when filling I opened the bleed valve and squeezed the large coolant hose a number of times while filling, which got the radiator as full as I could get it. I ran it for a few minutes and it's still topped off. So is this good to go?

Here's some other details that lead me to believe I might still have a problem. As I was letting the flush solution work its magic, I noticed a healthy amount of white smoke out of the tailpipe, which smells somewhat sweet. That's no good. Also, the first time I drained the flush + water mix, it came out in a good stream, then slowed to a trickle, then another heavy stream came out after a while, making a big mess. I think the very first stream was fairly cool, but afterwards the fluid that came out was steaming hot. Is this normal? What would this mean? Did I dislodge some kind of big clog? On the second flush of just tap water, it came out fairly consistently until the very end, and was consistently hot.

After the full flush and top-off, the system is still getting pretty warm while idling, though perhaps not rising as fast as before. I need to drive it around during the daytime to see what's really going on.

As for temperature checks to see if things are flowing correctly, I have suspicions that things aren't flowing as they should. Which parts of this system should be too warm to touch when the engine is up to temp? There are two metal hoses coming into the driver's side of the radiator - both of those were warm, but not hot, while the soft hoses were scaldingly hot. Is this right? And should the radiator have been cool to the touch from the front? I could put my hand on it and it wasn't even warm. What parts should I try to touch, to see if they get warm?

I also didn't notice the fan going into high gear when the engine temp went up. Shouldn't it kick in once the coolant temp gets above a critical point? The only time it sped up was when I turned the engine over. As I understand it, the fan has two speed modes - ~20-30% of crankshaft speed, and ~70-80% of crankshaft speed. Assuming I was just sitting there at idle, I would wager that I would notice a change in sound if this thing kicked in, right? Does that mean I should perhaps replace the fan clutch after all?

Do any of these symptoms sound like I might have a clogged line in the radiator somewhere? Or perhaps the water pump just isn't working at all? When I step on the gas in park the temp goes down very quickly, so something is working right, but I have no idea what possible things are working wrong.

 

[Denisefwd93]

Hope you aren't putting cold water in a hot engine, I'm of the old school mindset on removing the t-stat when flushing the system.. Water won't pump/flow when t-stat is closed but will flow through the heater if the heat is on Re-read Ron'sadvice, did you the purge the heater core?
White exhaust .....
Fan clutch still may be a problem it doesn't have speeds, warmer it gets the more the clutch resists the free wheeling ... unless... you don't have an electric fan on there do you?

 

[DoctorRoboto]

I did purge the heater core, hooked up a line directly to what I think is the outlet (hopefully the PO hooked it up correctly, from the t-stat is on the right, from the water pump is on the left) and let it run until it came out clear. Not too much gunk in there.

I'll have to do a bit of driving today to see what happens.

 

[DoctorRoboto]

Okay, some updates on this. Loaded to the gills, with 1000 pounds in tow, I just drove the truck from DC to Portland, 3000 miles over 7 days. No overheating except when heading uphill in an overly low gear, but downshifting fixed it. Sitting at idle on a hot day is fine as well. Checked radiator a few days in while cold, was now filled to the top unlike before. The fluid in the reservoir eventually got cloudy and rust colored, likely didn't flush everything perfectly with the flush kit. But it works. The problem was definitely the clogged overflow hose to the reservoir, which was a free fix.

The problem is that it still has a white puff of smoke on startup, and a slightly sweet burning smell while running. I may have put in a tiny bit of coolant into the reservoir at one point, but only a pint of so. I did have to put in about 2 quarts of oil over the week, and it was full when I left. Could that be the source of the white smoke, or is that likely coolant?

My guess is that this is what happened - PO had the block, engine overheated and messed up head gasket slightly, maybe even warped something. He gave up on it and sold it, not knowing the cause.

How hard is it to swap the head gasket? Is that literally all you would do, or would you hone cylinders and lap valves? Would swapping the gasket fix the burning smell and restore compression on one cylinder (down to 120, others are around 150-170), if that's all I do? Are there other easy things to fix if I tear into the cylinder head?

 

[Rearanger]

Have a used oil analysis done to determine if and how much coolant in oil.

Here