So is it worth a replacement motor?

 

The body is in excellent condition and considering all the new parts, I think it would be worth it if I found a good used engine.

 

If you find little difference between cylinders warm up the motor. If still little difference between adjoining cylinders it's time to poke around the motor some more. I know you mentioned bubbles but it could be just a coincidence that you have two problems and neither being a fallen liner. You said that your not loosing coolant so lets hope for the best still.

 

wonder if listening to valve cover with stick or screw driver might narrow it down.

wonder if removing plug wires one at a time might lead to a sharp change in noise - which could mean something else (valve train, bearing, piston rod, etc.). perhaps with no ignition in the cylinder the sleeve would still slip for a modest period.

 

Why don't you try some visual inspection stuff like pulling each plug for comparison. If there is an ignition (lack thereof) issue, it should be apparent from the appearance of the plugs I would think.

That is free and may point you in the right direction. I would also thik a compression test would be helpful in evaluating what is wrong instead of what MAY BE WRONG.

Wild *** guesses can be very costly as most of us have found out in one way or another.

And with some luck maybe a used motor will be one alternative or some reasonable repair to yours.

I have seen rebuilt heads available for exchange from a couple of trusted sources.

 

Well, I pulled the plugs and all look the same with no clean or gunked up plugs. I tried to pressure test the coolant system and it held 15psi. I did a block test with the liquid and it did not detect gases in the coolant. I did not do a compression test. I did notice when the temp starts to go up on the gauge if I turn the motor off to the key on position, the temp gauge immediately drops to normal level. The second I start it up it climbs again. Is this normal? Could the temp sender be defective? I unplugged the two prong sensor and it did not change the gauge readings. Unplugging the single wire sensor resulted in no reading on the gauge. The wire to the single wire sensor appeared to be slightly bent on the top. Do both of these sensors detect coolant temperature?

 

I stuck a thermometer in the radiator hole with the engine running at operating temp. I could not leave it in there too long as coolant was starting to overflow, but there was a difference between the thermometer and the OBDII reading. The OBDII reading from a scangauge was showing 215 while the thermometer was showing 195. With everything closed up, the OBDII reading was showing and would not budge past 231.8max and would not go higher but the gauge was in the upper region almost touching the top line.

 

1. 2 prong sensor drives the ECU, this is what you see on scanner. Trust this. It is one on right in pix.

2. Single wire sender is gauge only. Don't trust this. It is one on left in pix. Can be impacted by gunk on the sender terminal post shorting slightly to ground. Both sensors can have "scale" on them, throwing off reading, but not making overheat issue.

3. Both senders located near thermostat and slightly above. If you have a steam pocket behind the stat the senders will be in/out of the hot water. Think the steam is hot? It is, but next time you make pasta hold had over pot. Then put hand in the pot. (Please don't , this is just an example). Point is that thermostat, and sensors need to be immersed in water. If you stat does not have a jiggle device or 1/8 hole in the flange there could be a steam pocket build up. The vent hole or jiggle device go at 12:00. The spring of the thermostat goes in the block (some others may not know that).

Both sensors will be skewed if wires grounded to them, even slightly.

4. A $10 new thermostat might be a good idea at this point.

5. Yes, the temp inside the block will be more than the water temp at the radiator bung hole.

6. Check radiator fin surface after warmed up - should be with 10F top to bottom. You replaced the rad. Used ($50)? New copper/brass ($450 - $700)? New aluminum (232)? If a used unit, it may have calcium buildup. If a unit shipped from east Egypt, could have packing material inside, shop rag, etc.

7. Recheck fan belt route and fan blades orientation - air blows toward block, not out the grille.

8. My D1 with 180K + does 180 - 183 on the highway with a 180F stat.

9. Any gurgle sounds under dash for gas bubbles in coolant? Assumes heater core is not bypassed. Is system bled enough?

10. Water pump - if belt is on wrong it will run reverse direction. If blades missing, it won't pump enough. Spec is 2.64 gallons per minute at 1000 rpm, so I guess it could be tested with a five gallon pail. But a $3 gasket allows you to inspect it. If replacing there are after market ones with a larger bronze impreller.

Everything you have found says overheating, but no coolant loss, white smoke out the back, exhaust gas in coolant, coolant in oil, etc. So if it is full of coolant, radiator is OK, thermostat is trusted (you can "boil" it on the stove to test), then water pump is on the short list (either by missing blades, belt route, etc.). Once you are going 50 mph, fan does not count, unless it too is reverse mounted or running bass ackwards. The coolant pressure cap should be holding pressure of course.

 

I found one possible problem. The pos thermostat was stuck closed and would not even open in boiling water. It was replaced 1 yr ago and is a Mr. Gasket "High Performance" 180 degree thermostat #4364. With the thermostat removed engine temp did not get above 210 while at idle for 30 mins in 90 degree heat. The temp immediately dropped when I started to drive down into the 190s.

 

Further driving and the temp is around 180-190 while moving. It looks like that thermostat may have been the problem. Got under the truck, and the rattle sounds like it could be the converter. Truck will be put up for sale...maybe a die hard enthusiast will want it as it has just about every new part except a new engine. For the year, it is in mint condition.