I found a 71 duster with 50,000 miles all orig. auto trans., air, all stock and original. After doing a break job I have driven it a few times but not to far at a time. Last weekend I took it on a road trip. It drove out great but did show to run hot after a while. What was strange was that it would heat up running 65 to 70 on the freeway, but would cool down when I slowed down to 30 or 40 on side roads. That is the opposite of what I have seen in the past. The cooling system has a fan with no clutch, no leaks or water loss that I can find. It still has the stock shroud, and all the hoses appear to be good. The radiator isnt leaking but who knows if it has ever been cleaned. Looks like a new cap on the radiator. It didnt get hot enough to smell hot or see any steam but the gauge would ease up to around 250 when running down the road at 65. Any one got a good idea where I should start?
71 Duster slant 6 cooling?
- Thread starter mike rat
- Start date
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Sussmad
Well-Known Member
- Joined
- Jun 19, 2009
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I would say the radiator is suspect. All of my cars have been slant 6s and I had one that did exactly what you described, fine at high speeds, hot in town. Those radiators are easily available; 1-800-radiator carries them for less than $200. I don't know about the quality. Also I see that FABO member mshred has one for sale. enjoy.
Cooter
Well-Known Member
is the manifold valve stuck? It will likely run hot at all speeds if this is open, but check it anyhow.
slantsixdan
=..=
The manifold heat control valve will not cause engine overheating no matter what -- stuck open, stuck closed, missing, whatever.
High-speed overheating is a water flow problem, not an air flow problem. The radiator is a prime suspect; see here for what I found in my low-miles '73 last autumn when I bought it. And the thermostat will definitely want replaced (use a Stant SuperStat 180° unit, part number 45358 ). But there are other common causes of slant-6 heatup that likely need addressed, too; see here and here. The other common issue with slant-6s with original-type shim steel head gaskets is that the coolant blockoff often rusts right through, allowing coolant to take a short path into and out of the head instead of forcing it to circulate through the entire head. That causes the rear cylinders to run hot, which causes pinging that can't be controlled by the usual means of high-test gas, reduced ignition timing advance and colder spark plugs. You and I are in the same boat: we've both got nice low-miles original slant-6 cars, and we're both facing some heavy lifting (remove head, clean out block, replace head gasket).
High-speed overheating is a water flow problem, not an air flow problem. The radiator is a prime suspect; see here for what I found in my low-miles '73 last autumn when I bought it. And the thermostat will definitely want replaced (use a Stant SuperStat 180° unit, part number 45358 ). But there are other common causes of slant-6 heatup that likely need addressed, too; see here and here. The other common issue with slant-6s with original-type shim steel head gaskets is that the coolant blockoff often rusts right through, allowing coolant to take a short path into and out of the head instead of forcing it to circulate through the entire head. That causes the rear cylinders to run hot, which causes pinging that can't be controlled by the usual means of high-test gas, reduced ignition timing advance and colder spark plugs. You and I are in the same boat: we've both got nice low-miles original slant-6 cars, and we're both facing some heavy lifting (remove head, clean out block, replace head gasket).
340mopar
Sorgermotorsports
If your motor was running on the lean side it would show up more at higher speeds than slower speeds.
Chuck
Chuck
slantsixdan
=..=
H'm. What would you have him do in response to your experience? It happened to you -- yes. It can happen to anyone, with any kind of fan. But it almost never happens to anyone; it's just not something worth worrying about or spending money, time, or effort on.
71dartswinger
Well-Known Member
i live i Florida and mine was fine in 95 degree bumper to bumper traffic but get on interstate and it would get to half way on gauge around town only to 1/4
radiator was 70 percent plugged replaced 8 years ago and runs at 1/4 all the time
radiator was 70 percent plugged replaced 8 years ago and runs at 1/4 all the time
Pulled the radiator this week end and took it to the radiator shop today. It was full when I started draining it, I opened the petcock and fluid barely ran out so I opened the cap so it could vent and it still almost hadnt drained all the way by the time I had removed the hoses, auto trans lines, shroud, and loosened the support bolts. My friend at the radiator shop told me it might be better to buy a new one. This was at least one of my problems.
I hope you flushed your engine out real good before hooking up the new radiator!
Later,
Bruce B.
Later,
Bruce B.
cudadriver
Well-Known Member
If you get overheating at high speeds it could be that someone has removed the wire coil from the lower rad hose. This coil keeps the lower hose from collapsing at high speeds. Just a thought.
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