overheating issues

[eighty_six_720]

So last weekend I drove the new truck out to to my buddies house in the desert (at night) and going up through the mountains the truck was getting a little too hot, about 3/4 of the way up the temp gauge. I pulled over for a while and waited for it to cool down and once out of the mountains everything seemed fine. On the way home however(at night again) the truck seemed sluggish and would get too hot too frequently to the point where the headers were glowing red and I was stopping every fifty or so miles. Now that I'm back the truck seems sluggish and hesitates and backfires every time I step on the throttle. Any help would be appreciated. Here's the truck if anyone's interested

 

 

 

[Z-train]

Headers glowing?Timing issue or big time lean.

[72O]

Damn that rig is a beauty. I just had the same issue with mine last weekend. When was your last tune up? I would reset the timing chain and check your cooling system. Nice 4x4 though. 

[datzenmike]

May have a blown (or soon to blow) head gasket. Keep an eye on the water level... if it starts using water that's a sign. Steamy exhaust is another. Rad burping water out the overflow is another. Water can work down past the rings and mix with the oil making it a cafe au lait color.

[Boaty]

Ignition timing and/or lean fuel mixture.

 

Start with ignition timing. Checking timing is free and takes very little time.

Z24?

I know the 86.5 pickups used a half-year only fuel injection setup that was replaced with a more refined version in 87. If you're EFI, I would check fuel pressure & filter first, if those check out you can then rule out the fuel pump. Low pressure? Clogged filter, and/or bad, worn, or aged pump (it's kind of gettin' old ya know?). 02 sensors can cause oddities such as this. If it were a KA, I'd opt for thinking a bad or misadjusted/out of spec throttle position sensor. After 50 miles of cruising, that probably means nil throttle. Could just be leaning out.

But logic dictates heat is a lean mixture or advanced timing.
I bet it pings when you pull a grade at lower RPM, yes?

[eighty_six_720]

Thanks for all the responses guys I appreciate it. I've been having fuel system issues since I bought it so it could be the pump or the filter I dropped the tank a while back to clean it so it doesn't seem likely that it would be a clogged filter. Ill check both after school tomorrow. And I have been monitoring water levels and all seems well in that arena so hopefully that rules out head gasket. It is the carbureted z24 so it sounds like it might be timing. Might sound like a stupid question but how do I make sure the timing is lined up once I take off the valve cover? On top of all this there's a sort of hissing/whistling sound at freeway speeds if that means anything.

[datzenmike]

EFI on the 720 uses two wing nuts to hold the air filter on.

 

If you were roughing it maybe you got water on the dizzy cap or inside it?

 

 

I would check and clean the plugs and wires first. Won't cost anything and the plugs can be read to tell you what's going on inside the motor. Are they evenly clean? or are some VERY clean.

 

The glowing exhaust???? could be the exhaust side coil isn't working. The motor will be thus running extremely retarded on single plug operation. The motor will also run hot. Pull a plug wire on the exhaust side and put a plug in the end an lay on a grounded surface, crank the motor.... got spark?? If NO change the first fuse on the far left on the fuse box.

[eighty_six_720]

I took out all the plugs an it looks like the exhaust side isn't firing. I replaced the fuse on the far left but still nothin. My guess is the distributer

[datzenmike]

 .... wait a minute are you going by the look of the plugs???  Pull one, stick the wire on it, lay on a grounded surface like the valve cover and have someone crank the motor. This is the only way to be sure it is or isn't firing. Otherwise we could go chasing a problem that might not exist.

 

Modules never fail. Swap coils around if the intake stop firing then the exhaust coil is bad. You may even find a loose wire.

[eighty_six_720]

No I set it on a piece of sheet metal I had laying around and saw a whole lotta nothin. But I'll for sure swap the could around and try that before I do anything.

[MikeRL411]

No I set it on a piece of sheet metal I had laying around and saw a whole lotta nothin. But I'll for sure swap the could around and try that before I do anything.

 

Unless that piece of sheet metal was firmly connected to your engine block you proved nothing. 

[eighty_six_720]

I see. Didn't really think that one through huh? I didn't get much done today anyways ill check again using some of your guys advice tomorrow.

[godzirra]

I know its a really simple fix but mine had the same problem when I would make a run to the land fill (no more than 5 or 6 miles), it turns out the over-flow hose from the radiator and the cap to the reservoir were clogged solid (this was the original hose and cap from 1980), causing too much pressure build up in the radiator.  

[BlackBart]

Sorry for the necrobump, new owner of a 85 720, having overheating issue. Figured I'd bring this back up as some of it may be relevant, instead of starting a new "derr my truck runs badd derrfr" thread.

 

Drove truck 500+ miles after purchase, had it losing power and getting hot on every grade. Not too badly, but now I can't make it the thirty miles to town without temp gauge going past 3/4. Read the bit in this thread about the clogged radiator overflow hose, checked mine and found it quite clean, but the metal line coming from the cap area crimped in half.

 

https://m.flickr.com/#/photos/143334550@N05/28474749625/sizes/m/

 

That's as close as I can seem to get to actually posting a pic. Would this cause pressure buildup enough to heat my block up so much? It's burning a good bit of oil as well, but I feel (perhaps incorrectly) these problems are unrelated. Haven't checked timing, or even mixture yet, as I am wrench stupid.

 

Any advice or info would be groovy.

 

Also; been lurking, dig the community.

[datzenmike]

The overflow only lets excess pressure out to a collecting can, it doesn't cause it. 

 

Any time the temperature is an issue I recommend changing the thermostat right off. They wear out from age.

 

 

 

Watch the lower rad hose while you rev the engine. If it is excessively soft it will collapse from pump suction. Remember that rad hoses rot from the inside out and may look good.

 

Are you using coolant and needing to replace it weekly? If so the head gasket may be bad.

 

Excessively retarded timing will also dump lots of heat into the cooling system. This can be caused by one of the coils not firing. Check for spark on the intake and the exhaust side plugs. If the exhaust are not firing replace the first fuse on the far left hand side of the fuse box.

[BlackBart]

No collapsing of rad hose. No real loss of coolant, though I do notice now that the crimped line is dripping a negligible amount.

 

Both banks of plugs are getting spark. The wear is a good bit different on both banks, and the gap on the exhaust side plug I just pulled is less than .02 inches (won't slip on my little gauge at all).

 

https://m.flickr.com/#/photos/143334550@N05/28443229576/

 

That would be pretty sweet if a thermostat is all I need to keep burning oil til she does. I was just reading on this forum the soup test, maybe I should try that next.

[BlackBart]

Oh yeah, left plug in pic is intake, right plug is exhaust.

[datzenmike]

Plug gap would be 0.032 at least. Could be higher.

 

Buy a new gasket for the thermostat. 

[BlackBart]

Ride on with your right on, brother man.

 

Thanks to all you contributing members for the vast wealth of information here.

 

If'n that don't do it, I'll read the whole section again before I trouble y'all.

[datzenmike]

Make sure your rad shroud is in place around the fan. Shrouds increase cooling efficiency.

 

Clutch fan... Engine off try to turn the fan blades. They should turn with firm resistance. If free or loose turning, the silicon clutch oil has leaked out and the fan will not reach it's specified 1,500 RPMs at water pump speed of 4,000 RPMs. In other words it will be slipping. 

 

Rad fins are packed with bugs, leaves or dirt.

 

Take the rad cap off and drain enough coolant to expose the tops of the vertical cores. They should be clean and free of scale and deposits. Use only distilled water for the rad.

[BlackBart]

Shroud is good, fan clutch seems pretty packed still. Changed thermostat this morning, went for a drive and she still getting too hot. Limped home and found a pretty steady couple drips at a time coming out the new stat gasket. Thought I did everything by the book except applying silicone sealer.

 

Old tstat was burnt looking. Mightve been 10-15+ years old. No "jiggle valve" on it either. Rad looks relatively dirty inside, but I've had dirtier ones function properly on 80's fords. There was a decent bit of pitting on the stat housing and cover. Sanded out best I could, but I'm wondering if this leak wouldn't make temp climb as well...

 

Any more thoughts for an idjit?

[lctmjw]

The cooling system has to be free of leaks, even a small one can cause an overheat condition. Thr cooling system is pressurized and has to remain so to circulate coolant properly. Being under pressure also increases the boiling point of water. Mend up your leak before troubleshooting further.

[lctmjw]

Going back to your first post, headers are/were glowing red hot? Good advice already posted about checking spark and timing, but if your truck has a catalytic converter still, make sure it isn't clogged up. A clogged cat could explain the symptoms you've posted thus far.

[BlackBart]

Leak hopefully mended. Found some blue rtv from 1986 in one of my buckets of petrochemicals. I think my dumb ass overtorqued the bolts and ripped the gasket, but I'll see how it does after it dries a while.

 

OP had the glowing headers, I just have the heat.

 

How does I check cat? Remove and inspect? Is there a less bolt-breaking method perhaps?

[lctmjw]

Shit, I wasn't reading carefully enough, thought you were the op.

 

Checking cat without removal? Likely no way to know for sure without removing it, but shake the exhaust side to side if you can. If there's rattling in there, the material inside has collapsed some and can jam the exhaust. You can gently tap the cat itself too listening for rattling noise, but do so carefully.