still runnin hot, cant figure it out

[msgdsrf]

In another direction.. have you looked at your plugs? Could you be running lean at those speeds?

[JCD]

Originally Posted by RustyBucket

Mark, I'm curious as to why it would over heat with a 165 thermostat?... just askin'. Looks like after the coolant reaches the opening temp. of the thermostat and it opens up the thermostat's done all it's gonna do except provide some restriction to slow the coolant down....

X2 to Mark..

I had a 165 thermostat in the intake of my car, and it overheated when sitting in California traffic..

I had a radiator guy recommend a 195 thermostat and the problem went away.

It's actually a straight forward happening..
A thermostat opens up at the temp stamped on it.. On a 165 less time in the motor as the temp gets up to 165, and it opens.. that means less time shut and the water in the radiator has less time to cool down.

At 195.. the thermostat stays closed longer, allowing the water in the radiator to cool down more.

With a 165, if the motor reaches 165 or more, the thermostat stays open all the time, the water constantly flows through motor, and radiator not giving it any time to cool down.. motor temp keeps the water getting hotter and hotter til the inevitable blow..

So a lower temp thermostat is not always the best option for cooling a motor.

J

[69GWC]

Never thought about it like makes good since.
Posted via Mobile Device

[nele22]

if the above comments are true about the 165 thermo then I may have just found my overheating issue.
Posted via Mobile Device

[1972crewcab]

sounds like a trans issue to me . but everyone here is on the right track

[RustyBucket]

Here's ANOTHER one of those informative good reads on this site. I think the odd thing about JETFIXR's heating problem that it happens at higher speeds. Maybe it IS caused by the coolant speeding through the system too fast to dissipate heat 'cause of the 165 thermostat. Sure would be an easy fix. Hope that and maybe a big spring in the lower rad. hose cures it.
I've got a mechanical gauge on my Blazer so it keeps on reading after I shut it off. It'll get up around 200 deg. idling on a hot day w/the A/C on. It scares me when I shut it off, the temp. pops up to 240. I guess it's a good system test, it doesn't blow out the overflow or bust hoses or gaskets.

[j1970GMC]

Are you getting enough fuel? I had a similar overheating problem on my 67 and found out that the in tank fuel pump wasn't hooked up. I was getting enough fuel at ilde but not during high engine loads. I put a holley red fuel pump on and it's running great.

Probably not it but one more thing to think about...

[Xeen]

After reading some of the suggestions the cheapest thing to do is put the factory recommended temperature thermostat back in it and see if that cures the problem.

[prairewolf]

... Are the belts tight enough?, .. what does'nt slip at Idle may slip at a higher speed/rpm..... and I do not trust the 50/50 pre-mixed anti freeze. ...it is easy to put 50/50 on sticker on container and actually have a weaker mixture inside the jug. ........

[Stocker]

Originally Posted by RustyBucket

It scares me when I shut it off, the temp. pops up to 240. I guess it's a good system test, it doesn't blow out the overflow or bust hoses or gaskets.

Well, the entire system isn't getting that hot.... it's just a localized hot spot (from combustion chamber heat) in the head b/c the coolant is no longer circulating.

[RustyBucket]

.. both cyl. heads make a pretty big localized hot spot. Lots of cast iron to transfer heat around. Guess I could move the sensor to the intake manifold if I was curious.
I never had one but I'll bet the electric driven water pumps really cool them down quickly after you shut 'em off. No combustion heat AND the cooling system's still at work.

[mr48chev]

Originally Posted by prairewolf

... Are the belts tight enough?, .. what does'nt slip at Idle may slip at a higher speed/rpm..... and I do not trust the 50/50 pre-mixed anti freeze. ...it is easy to put 50/50 on sticker on container and actually have a weaker mixture inside the jug. ........

It's all too easy to make your own 50/50 antifreeze that you know is 50/50.

Take one full jug of 100% antifreeze and one empty antifreeze jug, pour half of the full jug into the empty on so you have two half full jugs. fill each back up with water and put the lids back on. Now you have two gallons of real 50/50 antifreeze for the price of one gallon of 100% antifreeze. But that is way too hard for a large number of people to figure out it seems.

Jetfixer, Exactly what "HOT" temperature have you seen on the gauge and exactly when and for how long?

Does it go 220? 230? 240? or just up to 205 and then right back down when you start moving again?

Is the radiator core clean and free of bugs, dirt and and oil and anything else that might hinder the air flow? The OT van that I just sold a week ago came to me cheap off Ebay several years ago when the previous owner burned up the engine because the hoses on the external trans cooler leaked and covered half the radaitor with trans fluid that got full of dirt and blocked a large percentage of airflow through the radiator.
It's an early truck so I doubt you have one of those cut out of sheet metal grills that some elements seem to like that look like they block 70% of the air to the radiator.

You do have the correct waterpump to match the belt/pulley system you have? I've seen that go wrong both ways with guys putting an early V belt engine with V belts in a Camaro that came with serpentine belts and then buying a water pump for the model of car rather than the engine setup. I've also seen trouble where a guy took a complete late engine and put it in a V belt truck and switched to V belts without swapping water pumps to match.

I still want to know how hot it actually is getting and when and for how long though.

[msgdsrf]

Originally Posted by Stocker

Well, the entire system isn't getting that hot.... it's just a localized hot spot (from combustion chamber heat) in the head b/c the coolant is no longer circulating.

I'll suggest lean mixture one last time.

[BuiltwithIvy]

Originally Posted by Stocker

My thoughts also. Unpressurized water boils at 212*. Pressurized 50/50 coolant boils several degrees higher -- I've seen the numbers but don't have them in front of me.

3 degrees per pound of pressure on the cap. Coolant actually boils faster than water, but when mixed its right under 212, 15 lb cap * 3 = 45 + 212 = 257

[pat 70/71]

I had a 327 once that would run great and then run hot. It turns out there was a small crack in one of the cylinders so small it would not pull water into the oil but, it would peg the temp gauge( steam pocket) After changing the radiator/ thermostat/fan/ water pump I purchased a zz4 create motor and all is well. I still have the 327 and one day I will sleeve it and run it. This was not easy for me figure out
(sounds like it would be) but it had me stumped for a while. Cheers, Pat
Posted via Mobile Device

[198plus]

What engine are you running, and what do you have your timming set at.

[blazercrazy70]

Could be head problem with the water jackets blocked. A buddy of mine had the same issues and did all the fixes mentioned and ended up pulling the motor down and found the heads plugged up not flowing very well had them redone problem fixed.

[Officer68]

don't forget to overlook fuel psi.....if you are running lean it will run hot at speed, at idle it will be fine. check fuel pressure at the carb and work backwards from there.

[198plus]

Originally Posted by 198plus

What engine are you running, and what do you have your timming set at.

If the timing isn't set right and your not running vacuum advance it will cause it to run hot.

[jetfixr]

Thanks all, it is food for thought, I have had pretty much the exact same results whether I run a 185 or a 165 t-stat. I have yet to pull the plugs to see if it is running lean, but when it idles it smells like it is running pretty rich. I keep trying different things, eventually I will hit on it. I can check to see if it is running lean becase that is cheap, but the water pump has to wait til next paycheck.

[GuyO]

The only thing left is it needs to be "burped"! Loosen the cap and drive it until the thermostat opens. Then park it nose up on an steep incline, with the cap loose - squeeze the top radiator hose sveral times and check for drop in coolent level. It really sounds like it has a air bubble that the pump can't force out.