Car has 57,000 miles on it. Been chasing a running too hot issue for several months now, which is getting more imperative with hotter weather coming. I've read about the tendency of these blocks to silt up toward the rear and fear that it may be time to pull the head to see about cleaning this out. Before pursuing this, which isn't anything I feel qualified to attempt myself, I figured it'd make sense to see if anyone has any other suggestion of something to try first.
So here's what I've done -
I've tried multiple thermostats and sensors, replaced the water pump, confirmed with a radiator shop that my radiator has no blockages, flushed the system with radiator flush additive and distilled water followed by distilled water only, gotten new OEM caps for the radiator and overflow tank and checked my compression (which was in spec) even though there were no signs of headgasket failure either in my oil or coolant. The timing is right on 10 degrees BTC. I'm not losing any coolant. I've confirmed that the voltage stabilizer (for the temp. and fuel gauges) and the temp. gauge itself are working correctly. Even swapped in a second instrument cluster that everything had tested OK on. With all this, the coolant has been replaced multiple times within the last 2 months and I'm using Zerex G5.
With an IR thermometer, I was able to see that there is a hot stop (as high as 234 F degrees) at the rear of the block next to where the rear head bolt is, which is only a few inches from the sensor for the temperature gauge. Along the rest of the head, between the valve cover and manifold, the temperature is around 192 degrees. Is it possible that this hot spot is effecting the sensor and that my car isn't really getting close to overheating though the gauge is almost in the red? I keep this problem in check by keeping my heater control valve wide open, but it'd be nice to actually fix this problem as I didn't even feel comfortable driving to Davis this year, which had been my goal. I also believe this could lead to failure of cylinders 5 + 6.
While all of my '71 164s (the most recent of which I owned 25 years ago) had a draincock by the oil filter, the '72 doesn't, so I can't back flush it there.
Time to have the head pulled? If so, I'm pretty sure that'll mean I'll have to replace the headgasket, so then won't I also need to make sure the head doesn't need to be skimmed first?
Suggestions? Have I missed something?
Thanks
So here's what I've done -
I've tried multiple thermostats and sensors, replaced the water pump, confirmed with a radiator shop that my radiator has no blockages, flushed the system with radiator flush additive and distilled water followed by distilled water only, gotten new OEM caps for the radiator and overflow tank and checked my compression (which was in spec) even though there were no signs of headgasket failure either in my oil or coolant. The timing is right on 10 degrees BTC. I'm not losing any coolant. I've confirmed that the voltage stabilizer (for the temp. and fuel gauges) and the temp. gauge itself are working correctly. Even swapped in a second instrument cluster that everything had tested OK on. With all this, the coolant has been replaced multiple times within the last 2 months and I'm using Zerex G5.
With an IR thermometer, I was able to see that there is a hot stop (as high as 234 F degrees) at the rear of the block next to where the rear head bolt is, which is only a few inches from the sensor for the temperature gauge. Along the rest of the head, between the valve cover and manifold, the temperature is around 192 degrees. Is it possible that this hot spot is effecting the sensor and that my car isn't really getting close to overheating though the gauge is almost in the red? I keep this problem in check by keeping my heater control valve wide open, but it'd be nice to actually fix this problem as I didn't even feel comfortable driving to Davis this year, which had been my goal. I also believe this could lead to failure of cylinders 5 + 6.
While all of my '71 164s (the most recent of which I owned 25 years ago) had a draincock by the oil filter, the '72 doesn't, so I can't back flush it there.
Time to have the head pulled? If so, I'm pretty sure that'll mean I'll have to replace the headgasket, so then won't I also need to make sure the head doesn't need to be skimmed first?
Suggestions? Have I missed something?
Thanks