Hi Gang,

This post pertains to a 1966 Dart /6 225, engine ID 2806830-6. Daily driver.

I recently put in a rebuilt motor. The rebuild was done by a reputable shop. My car is running very hot. Temp guage is pegged to the right. I freak out and kill the engine each time it gets all the way to the right. A meat thermometer shows the coolant at 180 degrees. I'm not sure I want to see if it gets any hotter as it is a like new engine.

Here is what I have tried/checked...

1. Replaced a 180 degree thermostat with a 195. The pellet is towards the interior of the head. What temp should the coolant be at if I pop the radiator cap and stick a thermometer in there?

2. For some reason, the previous radiator cap was 7 inch pounds. It is now 13 inch pounds.

3. Flushed heater core with water in both directions in case there was something blocking it. Double checked position of heater hoses with the hose coming out of the water pump going into the right side of the "double tube coupler thingie" at the firewall (from inside the compartment).

4. Temperature sending unit is new.

5. Water pump is new. This could be a source of the problem, perhaps. Is there a simple way to tell if the problem is a lack of antifreeze movement?

6. Radiator was re-cored but the shop painted the fins (arrgh!) with a weird thick paint. I stripped the paint of the fins as best I could with Stripeze and hosed it out real well. This could be a source of the problem as there is still some gunk in the fins. If I need a new radiator, where might I get one that doesn't suck at a decent price?

7. The car has a 4 fin fan. When holding a cigarette up near the radiator, the smoke blows into the engine compartment.

8. Timing is set at 4 degrees before TDC.

9. The bottom radiator hose does not "pinch" when warm.

10. My instrument cluster voltage regulator is one year old.

I'm at a complete loss. Any ideas.

Also, I have a 7 blade fan out in the shed. Would this partially help move more air?

Tom

Where are you sticking the meat thermometer when you measure?
Drain the coolant enough to allow you to remove the temp sending unit and make sure theres no gunk around it etc.. I believe they are cheap so getting a new one is good insurance.

I don't think paint on the outside of the radiator will be a big deal.

I know new engines run a bit hot untill everything is settled but enough to peg a gauge? I hope your rings/pistons aren't too tight. Do you have an oil pressure gauge in the system?

A 7 blade fan might move more air but a typical 4 blade should be plenty enough I would think. I've ran a 4 blade fan on my car since forever and on hard drives in 100+ deg heat the temp gauge wouldn't go past say 3/4

I have a 7 blade fixed unit on my car since my 5 blade clutch unit needed to be replaced...lets say that my gauge on a 90 degree day never gets past the first line with 50/50 and a 165 degree stat....

One of the more interesting trick the big block guys do is fire it up in their driveway with a garden hose stuck in the top of the radiator, run the engine at fast idle for few minutes, then rev it up and down to get the oil thrown around in there and get a nice wear pattern on the bump stick. Then shut it off, drain the system, use the right anti freeze and test drive it.

I think it's just your sending unit, but I wouldn't rule out anything in pierre's post. When I rebuilt my engine it never ran out of spec for the temp any time during break in....

best of luck,

-D.Idiot

p.s. who did your rebuild was it Ott's, Power Master's, or ???

With most factory guages, the first line of the temp guage's "running range" is 160 degrees, the end of the running range is 220 and pegged on hot "H" is 240.

180 degrees is not overheating, you may want to get an aftermarket temp guage just to cross-check.
Also drain down the radiator and look at the top of the core tubes, make sure ther is no scale or rust chunks plugging the top of the tubes. (New engines will often have a bunch of loose rust inside which can quickly plug-up a new radiator)
DD

Thanks for the tips.

I was taking the reading today from the radiator.

The radiator unit was flushed today so deposits aren't likely.

Tomorrow I will get another temperature sending unit. I will take the engine temperature while I have the old one out. If things do continue to heat up, what is the maximum temperature I should let the engine get to before shutting her down?

I do have an oil pressure guage. I will send the reading tomorrow night.

Thanks,

Tom

Are you sure you didn't accidentally damage the temp. sending unit wire while you were installing the engine? If it shorts to ground, you'll get a false reading...
Also, I had a similar occurance-high temp(gauge pegged) but none of the other unpleasant symptoms of overheating.
It turned out that the engine to body ground was deteriorated and apparently it was affecting the gauges.

Does the fuel gauge read high also? If it does, you most likely have a bad instrument voltage regulator.

_________________
Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Hi again,

Re: Loghead- I will double check the engine to body ground and the temp sending unit wire this evening.

Re: Charrlie_S- the fuel guage is working great.

Can you tell me what is the normal operating tempuraure range for a/6 225 is? I need to know when to kill my engine if it gets too hot so I won't damage anything.

Tom

When I got my 70 Valiant the temp and fuel gauges didn't work. It wasnt the voltage regulater it was the circut board. when I got it on the temp gage still didn't work so I got the temp gage from the same car as the circut board a 74 Valiant. well this gage read low with my 70 sending unit. I put the sending unit from the 74 Valiant in my car and finally the gage reads correctly. that tells me the newer sending unit sends a greater signal to the gage. Perhaps when the engine was rebuilt they put in a sending unit from a newer vehicle and it is just the wrong one for your 66 temp gage?

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So I checked the coolant temp inside the engine where the temperature sending unit goes. It reads 202 degrees farehnheight. I only ran it a minute after the temperature guage pegged all the way to the right. The temperature inside the radiator was 175 degrees.

Per Pierre's question, the oil pressure reads 50.

I'm thinking I'm in deep doo doo as there was an very light oily sheen in the antifreeze that shot out the temp sending unit hole.

Furthermore, I'm blowing some serious deposits out the exhaust, If I held up a piece of paper 6" from the end of the pipe, it would throw a black circle in a matter of minutes.

Any suggestions on what my problem(s) might be at this point? I obviously need to tow the car to a local shop and have it looked at as anything else is probably beyond my capacity.

Uhoh... oil in coolant eh... drain your oil and see if its milky or something funny in it. Sounds like a head gasket maybe? I'd tow it to the place that rebuilt your motor.

I'd say hook up a mechanical water temp guage, the kind with the copper core feed wire.

Then just run the car. Is the cam broke in yet? I had to start and stop my break in time (reed cam: 1hr above 2500-3000rpm) because i was getting too hot. So I did this about 5 or 6 times. Each time the temp needle would creep over to the right (stock guage and sending unit)

Then I drove the car 3,000 miles this summer running at the end of the range on the guage (220* by Docs info above). In the evenings it would run cooler like 195*, and during the day sometimes i'd put the heater on to keep it stable, especially during highway driving above 65mph. But I ran this thing pretty hot without it boiling over and it held together, hey it's a slant right? anyway, I desperately needed a better radiator, which i now have. Also, as the motor broke in and the temp came down a little, more gook from the fresh block clogged up the radiator worse and worse, so that kept it up. I remember seeing the water hardly move in the top tank, now it's like a river with the new rad.

I think you should be able to place a paper towel on the grill and have it stay in place. I took off my small /6 fan and put on a 17" 6 blade flex fan. It really sucks. I mean that in a good way.

So just run it hot, 220* isn't going to hurt it. Does it want to climb above that? is it getting hotter sitting or moving down the road?

Stay with the 13lb. cap for now, that will help you run it hot without it boiling over.

Oh yeah, forgot about the oil in the water thing. Hm. It could be the head or head gasket. Is the head rebuilt? checked for cracks? How long has the motor run, in total minutes of time? It may be of no concern, I'd say run it a few more times to determine what to do next.

j.

202 degrees F isn't anything at all. You're not even close to really overheating the motor. I'd get worried enough to shut it down if it gets much above 220. I'd drain and refill both the oil and coolant, and see if the oily sheen continues. Also, pay close attention to what the oil looks like, as someone else mentioned. If it's milky looking, time to start tearing it down to check for a blown head gasket, warped/cracked head, or (horrors) a cracked block. I think you can safely assume your stock gauge is reading wrong. Not that you shouldn't pay attention to your coolant temp, just that you ought to be using some other gauge to do it.

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Everyone driving slower than me is a moron. Everyone driving faster than me is an idiot. With all these morons and idiots on the road, I can't get anywhere!

just a comment on the oil sheen you see. a friend had a 500" big block done at a great machine shop around here but they dont take the time to change the solvent in the hot tank often enough and his motor took many flushes to get the oily gunk from the water jackets. almost cost him an aluminum radiator as well as gave him a bit of stress at first thinking a head gasket blew.

--chad

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74 swinger slant 6, the slowest, most fun car i have ever owned.

Hi Gang,
I just did an oil change (400 total miles on my rebuilt engine) and I think the oil in the antifreeze is not the real issue for identifying what the problem is with my hot running engine. Possibly a few drops worth of oil got in coolant when I was taking the temperature from where the sending unit goes while trying to capture most of the coolant in a tub placed below the engine. I did put a 180 degree thermostat back in and also ran the engine without a thermostat to see if the water pump was working OK, which it is. The temperatrure guage is still pegging all the way to the right. I have an appointment this Friday at a reputable shop and will have the pros take a look at it. Is there anything you would reccomend that I have them look at as a possible source of the excess heat. I'm thinking at this point that it is not the temperature sending unit, water pump, radiator, radiator cap, clogged heater core, thermostat, faulty guage, etc... more like something inside the engine. Maybe this one is just taking a while to break in.

Thanks for all you help thus far.

I'll keep you posted.

Tom