Heat Soak Issue

[Abomb9182]

I have a 1971 Dodge Charger 500 with a 400ci and automatic transmission. not sure what the engine came out of (original 383 car). I have been having overheating / heat soak issues for a some time now. Driving down the highway temp stays steady at 180. If I come to a stop and shut the car off I can feel the coolant boiling / bubbling when I grab the top rad hose. I can also watch the temperature climb from 180 to as high as 215. That was out driving today with temps around 10C/50F. I have driven for over an hour before and temp stays good till I shut the car off. If I leave the car idling it will stay around 180 also. I think the issue is I have a hot spot in the block somewhere, like the coolant doesn't circulate through the whole block just keeps the front cool (by the temp sensor). Then when I shut the engine off the coolant temp balances inside the block to give me the high reading and the bubbling. I don't think it is a head gasket issue because I always have good heat from the heater core & don't smell any coolant in the exhaust. I do also have an electronic heater valve on the heater core. I do have an aftermarket ac system from vintage air installed also, but this issue also happens with out the ac on.

Things I have tried:
1. Upgrade Radiator from 22" Champion To 26" Griffin
2. Upgrade water pump from stock to high flow Milodon High Volume
3. Install proper fan shroud for 26" Rad
4. Hoard radiator in so air has to go through rad and not around it
5. Thermostats: 160, 180 & 195

Things it might be?:
1. Heater valve in the off position doesn't allow proper flow through block? (I have tried running without the heater valve and if I remember correctly it didn't help / I can try again)
2. Water pump not turning the right direction / impeller not working properly with housing?

I hope you can make sense of my rambling, any help would be great.

1971 Dodge Charger 500
400 BB
727 Automatic
Holley Sniper EFI
Vintage Air AC

 

[davek]

how long have you had the car?Did it just start doing this? Did you flush the engine when installing new radiator?

 

[twecomm]

Where is your timing set ?

 

[Abomb9182]

I got the car running about 4 years ago, it has been doing this since then. But seems to be getting worse. I did drain and flush the block several times before changing the rad. Timing is around 10 degrees at idle I believe. It has done this with the stock distributor and also I installed a Holley sniper distributor and same thing.

 

[Don Frelier]

The coolant shouldn't boil at 215. If it doesn't actually run hot I don't see a big problem. After you shut it off and stop removing the heat the block temperature will always rise.

 

[Abomb9182]

I agree the coolant shouldn't be boiling at 215. I am concerned because it sure acts like it is boiling by the sound and feel of the hose. So I am worried it is boiling just at a hot spot in the block. The bubbling / boiling is concerning to me.

 

[turbine68rt]

The coolant is boiling at a reading of around 215? If it was straight water I could see that but if you have a good antifreeze mix that shouldn't boil until closer to 250 under pressure. Can you take an actual reading of the coolant and compare that to your gauge reading?

 

[Abomb9182]

Yeah I definitely can get an actual temp, but right now my factory gauge and my Holley sniper sender both say the same thing. For coolant I use a 50/50 Premix and have tried adding Lucas coolant additive.

 

[davek]

might be a water jacket plugged

 

[khryslerkid]

Throw a little more timing at it and see if it makes a difference. If it starts pinging back it off a bit.

The more water you can have in the antifreeze the better. Water displaces heat better than antifreeze. Living where you do it may not be an option.

Kool it and Water Wetter does help.

Non ethanol gas helps.

When you top off the cooling system do not place the cap on the radiator until you see coolant circulating. This means the thermostat has opened. Placing the cap on before you see this will trap air in the system.

If you're running at 180 and it only goes up to 215 after shutting it off, that's normal.

 

[1967coronet]

Also you may get some help from a new 16# cap

 

[Ernie ingling]

15 psi radiator cap and 160 thermostat Timing too advanced
Efi running to lean.
Was block flushed and block drain plugs removed?

 

[PlainfieldCharger]

Thermostat installed in the correct direction?
With the car cool. Take of the radiator cap Start the engine, with a IR temp sensing gun measure the temp of the coolant when you see the thermostat open. Watch the flow....Too fast and too slow are not good..

FYI

I would tell you I had the same problem. I had bought a new radiator before the car was done. When I did finally get the car running it ran great for a couple of years. It started to overheating over time...
Ended up being the NEW Radiator clogged from all the rust from breaking loose in the block. The previous owner did not flush this block....
Gano filter installed and many flushes and a new radiator. Problem gone....

 

[Abomb9182]

Block flushed several time with block drians pulled. Rad flows great / no cores plugged. I will try timing and afr. Thermostat installed in correct direction. I guess the main thing I am wondering is it possible or if someone has had a hot spot in the block causing the bubbling / boiling issue? Like so much rust built up around one piston to cause this? I did have lots of rust and debris come out when I flushed the block, but maybe it is hard enough water won't flush it out?

 

[turbine68rt]

If the coolant is actually boiling that only happens at a given temperature. The sending unit or gauge might not be giving an accurate reading.

 

[1967coronet]

Evapo rust sells a radiator/block flush. Drain system, remove thermostat, use 2 qts of the evapo rust block cleaner and fill with water.
For it to work you must run it for a couple weeks with some miles and hrs on the system.
Reason I say 2 weeks is most folks do not drive their classic that much and this stuff works but needs time to do it.
after 2 weeks pull both top and bottom hose,s and flush with a garden hose engine and radiator several times or until it runs clear.

You will be shocked at the crap thats going to come out if the engine has not been boiled before.

 

[Abomb9182]

Just test drove it today again and I found the rad cap wasn't sealing. I will pick up another one tomorrow. That should take care of the boiling issue and maybe I am being paranoid about the heat soak.

 

[Ernie ingling]

Bingo

 

[khryslerkid]

Just test drove it today again and I found the rad cap wasn't sealing. I will pick up another one tomorrow. That should take care of the boiling issue and maybe I am being paranoid about the heat soak.

Bad cap not sealing is probably the noise you were hearing.

 

[Demonic]

Are you using the standard thermostats or the high flow type?