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| Engine overheating problem https://slantsix.org/forum/viewtopic.php?t=48567 |
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| Author: | Southmark [ Wed Apr 18, 2012 8:33 am ] |
| Post subject: | Engine overheating problem |
Bought a '60 Valiant over a year ago with 65k original miles on the stock engine. Ran OK but when I opened it up it was very gunked up (it hadn't seen many paved roads) so I had it professionally rebuilt. Had to bore it .060 over to get cylinders cleaned up, cut the head .040 and had a mild cam put it, split the manifold Block boiled out, radiator cleaned and flushed, new water pump, new t-stat, new radiator cap, new hoses, removed the heater, new temp sender. Now it runs hot - very hot -pegs the guage in 7 miles. 50% anti-freeze and a water wetter. BTW oil is clear and clean. I'm at a loss! Would the overbore and cutting the head make it run that much hotter? Do I need a bigger radiator? Would appreciate any help or suggestions. Thanks. |
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| Author: | KBB_of_TMC [ Wed Apr 18, 2012 10:31 am ] |
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Many things can cause overheating, but first check the basics. Personally, I've found that most of my overheating was caused by pressure leaks, so now I pressure test the system every time I close it back up. I had terrible overheating problems with a rebuilt 383ci Mopar engine, and found that no sealant had been used on any fasteners through the water jacket - after I pulled every bolt and stud and resealed them, the problem was fixed. The rebuilder just told me he expected rust to seal the just-rebuilt engine and to ignore the overheating and pegged temperature gauge. Next, radiator caps and thermostats do go bad - my Stant caps seem to go bad and not hold pressure after one good overheating; I test every thermostat and cap I put in before I install it. I've only encountered only definitely one bad thermostat. Check that there's not something (cardboard?) blocking air flow (my father put cardboard into his /6 Dart in one very cold Mich. winter, but forgot to remove it in the spring). I doubt you have a clutch fan, but if you do check that it's working. Check that the heat riser valve is not sticking and that the exhaust isn't restricted, then the radiator to see if it's cruded up inside. I found it cheaper to buy a new radiator than to have the old rebuilt. The A/F mixture could be way too lean, but then probably wouldn't run well. There are many other possible causes. Good luck! |
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| Author: | Aggressive Ted [ Wed Apr 18, 2012 9:08 pm ] |
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What temp T-stat did you install? How many miles since break-in? Sometimes a fresh motor may run a little hotter until broken in. Mine sure did.... What condition is the radiator in? |
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| Author: | Slanted Opinion [ Thu Apr 19, 2012 4:17 am ] |
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Does it overheat if you are simply parked and running at a fast idle? If it only overheats while driving, then I would look at the radiator, assuming you've ruled out all the usual suspects (collapsing lower hose, thermostat in backwards (happened to me!), etc) Any chance the fan is on backwards? The raise in HP (by increasing compression and overbore) shouldn't make a difference in this case... the stock rad should work, if it's working well. - Mac |
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| Author: | Southmark [ Thu Apr 19, 2012 8:49 am ] |
| Post subject: | |
Really appreciate the response, guys. Early on, when it ran hot, I removed the t-stat and replaced it with an orifice plate with a 3/4" hole - no difference. Runs hot at a fast idle or on the road. Radiator was flushed and cleaned while the engine was being rebuilt and the engine didn't run hot before being rebuilt. Engine runs strong. Tried different radiator cap - no difference. I didn't think the slightly "warmed" up engine would make it run hot - there is something I'm missing and I'm not ready to invest in a bigger radiator just yet. Hadn't considered bolt sealing thru the water jacket. Don't think the temp sending unit is bad as I can tell by feel it's truly hot. Thanks again for the input. |
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| Author: | Fopar [ Thu Apr 19, 2012 9:10 am ] |
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Drain down the radiator and look for crud blocking tubes. The modern cleaning of engine blocks doesn't remove crud from water jacket like the old caustic hot tanking. After drying out the old crud will start to flake off and clog the cores in the radiator. Richard |
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| Author: | SlantSixDan [ Thu Apr 19, 2012 9:26 am ] |
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Quote: I removed the t-stat and replaced it with an orifice plate with a 3/4" hole
Interesting test. Hole sounds too small, but if no change, the thermostat's probably not the cause. What thermostat did you put (back) in?Quote: Radiator was flushed and cleaned
Yeah, that's not gonna get the job done, given your description of the engine being well beyond needing just a flush and clean. I hope the water passages in the block and head were thoroughly cleaned out during the buildup.Quote: I'm not ready to invest in a bigger radiator
I don't think you have a choice about it. But just in case you might, tell us about the water pump in very specific detail. The 1960 170 engines used a pump with a smaller impeller (3¼") than was used on all other slant-6s (3½" on 225s right from the start in 1960 and 170s starting in '61). The small-impeller water pump has been N/A for years, and the big-impeller pump sometimes doesn't fit a '60 170 correctly without some block grinding. Do you see evidence of coolant circulation?"Unsealed fasteners through the water jacket" aren't causing your overheating problem. Lack of cooling system pressure generally does not cause overheating as such. It can cause the coolant to boil at a lower temperature than it should, but that's not the same thing and doesn't sound like what you're experiencing. (And anyhow, if there were sufficient leakage through "unsealed fasteners" to drop coolant pressure measurably, there would be a lake of coolant under the car and a steamy mess under the hood). |
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| Author: | wormswiggleinn [ Thu Apr 19, 2012 8:58 pm ] |
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Had a similar problem on mine finally checked the "new" water pump, impeller was backwards! Must of been for a boat motor cured mine |
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| Author: | Southmark [ Mon Apr 23, 2012 4:51 pm ] |
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As is often the case, the problem is simple. I should have replaced the temperature sensor early on but as it was new, I assumed[/u][/b] it to be OK. Bought a new temp gauge and, you guessed it, it wasn't running hot after all. It runs at 185 degrees (+-). I've worried with this thing for weeks and the temp sersor was either incorrect for the application or defective. Thanks to each of you for your response and to the moderators for establishing and maintaining the forum as an invaluable resource. Best regards, |
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| Author: | wormswiggleinn [ Mon Apr 23, 2012 6:30 pm ] |
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one more six on the road! |
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| Author: | slant6kindaguy [ Wed May 02, 2012 6:09 pm ] |
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"one more six on the road!"
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| Author: | Dltarnnr [ Thu Jun 07, 2012 12:07 pm ] |
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After 14 yrs of being tossed aside ,have been working for 5 months to get her road worthy.Sounds and runs like a champ but the long jaunts she starts acting up when at idle .The temp gauge dont work but just sounds like shes hot.If was internal rings etc would it not act that way all the time? |
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| Author: | Doc [ Thu Jun 07, 2012 1:34 pm ] |
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Have you checked - adjusted the valve lash? The hotter the engine gets, the less lash clearance you have. DD |
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