OK, updating this thread with my experience and some more questions.
As I have mentioned here and elsewhere, Poppy (
aka my '70 Polara 'vert) still has its original non-A/C 318 and 19" radiator (Part number P/N 2998951). The car had 31,208 miles when I purchased it. Right after I bought it in late March 2018, I had (i) the water pump replaced, as the original was beyond hope and (ii) the original rad recored. I started driving the car that the following month, in April 2018. Now, almost 15 months later, Poppy has been to two Carlisle shows and is just shy of 33,000 miles.
Here is my assessment of the cooling performance in those 1,750 miles:
1. Once it's hot outside (80+) and we're in town, the engine quickly starts to run hot. The temperature creeps up fairly fast: after a few minutes of driving in stop-and-go traffic, the temp meter needle reaches the high end of the "normal range bar", and after less than 5' it exceeds it (while staying in the range of non-lethal temps). Not great, as I have to try and avoid such situations -- and thus I have to overthink outings and routes.
2. As for the open road:
a. Last year, I did not have
any issue with temps while driving on either small roads or highways (even when keeping up with the fast traffic on the outside lane). Temps outside did not matter: the needle was between the E and the M, just where I like it.
b. This year, I had zero issue until this weekend -- but yesterday, Poppy overheated on the way back from Carlisle. This came after less than 75' of continuous driving time: 15' in Carlisle (got hot as per usual, but no overheating), 30' on small hilly roads at 40-60 mph (the temp quickly dropped but remained a bit higher than I usually see it, about 60% of the way right in the normal temp range
vs. 40% usually), followed by about 30' on the highway (where I spent all the time on the passing lane, driving with the fast traffic). Right around Emittsburg, just when I was thinking that life was really great, I smelled a burning smell: I looked at the temp gauge, and boy was it hot! I pulled over, saw steam coming out from the radiator top nipple (the steam pressure had blown away the overflow hose -- see pic below). I waited 20', then added a half gallon of distilled water. Afterwards, I had to stop every 15' to let the car cool down a bit, as temps kept creeping up after 5-10' of normal driving and reached the high end of my preferred range after about 15'.
Now for my questions:
why?
-->
Leaks? Don't think so. I had checked coolant level before heading out to Carlisle, and only needed to add a very tiny bit at that time to cover the gills inside. Every time I stopped on the way back from PA, I checked for leaks -- I saw none. Zero, zip. No marks in my garage either, ever. At first pass, it seems that leaks are out.
-->
Hose spring? My recollection is that, when Poppy was brought back in shape last April, my restorer put in an anti-collapse spring in the lower radiator hose -- otherwise, collapse and starvation would have been my first suspect. I'll double-check with him tomorrow.
--> The
thermostat is next in the suspect line-up. The original was replaced last year, but I just looked up the invoice and I was billed $14.75 for the one installed so I have no idea which brand the new one is (I made the same mistake as with the water pump, I did not discuss choices with my mechanic and did not keep brand records for parts in the early stages of the restoration). I am thinking that perhaps the new thermostat has already gone bad and in particular, as
@Big_John might say, has started "to stick or open later" -- which would explain the seemingly inconsistent temp behavior (goes a bit up, then goes a bit down) that I observed in my last 20-30 miles of driving before parking the car yesterday. Regardless, as
@mr. fix it stated, replacing the thermostat should not
solve the "hot in stop-and-go traffic" issue.
--> Of course, there could be an issue with the recored
radiator itself. I don't think the initial re-coring was the issue (otherwise, why did the car work perfectly once underway last year?). Maybe now there is a clog of some sort, but I doubt it. Yes, there is some oiliness in the coolant (see the second photo), though, so I'll have the system flushed anyways.
--> Next, I have to worry about the water
pump flow?
(i) As mentioned above, I don't know the brand of the pump that was put in. Perhaps the thermostat / pump combo is not the ideal one?
(ii) more broadly, after reading
this post from
@Davea Lux about the importance of keeping the "pump mated to the clutch fan and the pulley size", I am wondering whether maybe I have
mis-matched components? I doubt it in my case, as my restorer is a '60s-'70's Mopar specialist, but that is always possible. A question I will specifically ask him is whether the water pump housing is still the original one, or a replacement part (thanks to
@CBODY67 for
making me think of this possibility, and to
@Rapidtrans777 for also
suggesting to check the housing).
--> Finally, the radiator I have still has the original four-blade fan, but no
fan shroud. I have not been able to find any factory shroud listed for my engine, but
@1970FuryConv did manage to find a shroud and spacer. I've asked him about it, will post here when he responds -- and of course I am open to suggestions (pluses/minuses).
Look forward to hearing the best and brightest's collective opinions! If anyone disagrees with part or all of what I just wrote, or if I am missing an obvious item, please let me know where I am erring.