Overheating at idle on really hot days

[Biggredd2069]

My 68 Newport 383 is running pretty good now. However the reality is it's enjoyable to drive in the summer and August can get pretty hot. Went through a drive through on low to mid 90 degree day and couldn't really get out of line once I was in. The engine started to overheat and I shut it off before any danger but figured I'd ask for recommendations on cooling while idling. Once I got on the road the temp when back down and I felt pretty comfortable. I don't seem to be losing any coolant other than in those situations. I could swap out the thermostat possible? Should I get a better fan?

 

[Snotty]

How do you know it started to overheat? Do you have a temperature gauge or an idiot light? Cars getting warm in traffic is not uncommon, or a really large problem. However, if your radiator was belching coolant, that would be another matter.

I will say I had this problem, idiot light coming on and radiator burping, until I had my radiator rebuilt and a third row added. I also added a closed overflow bottle. No problems since, and I live in an area that gets over 105 often in the summer months.

You can see the bottle in this picture.

 

[Biggredd2069]

I have a Fitech fuel injection system with a digital readout computer. Was pushing 225

 

[thrashingcows]

Few questions to help us determine what's going on and help you solve your issue.

What radiator are you running....old, new, recored?
Do you have a shroud?
Also what kind of fan....4, 5, 6, 7, blade?
Solid fixed fan or clutched?
What temp termostat?

 

[Biggredd2069]

likely original radiator. I'm not at home but I think it's a 5 blade, fixed. Not sure on the thermostat, I haven't changed it since owning it. Does have a new water pump as well.

 

[thrashingcows]

Do you have a shroud? That is one of the biggest things for cooling, without it you can over heat easily at idle since the fant will just move air around in the engine compartment and not pull it through the radiator.

 

[Biggredd2069]

yes, I have a good condition shroud.

 

[Ccas]

What has changed about your combination from the past? You said 'got it running pretty good now' like it wasn't running good previous?

225 is not overheating. However, it sounds like if you sat longer, it would keep going. When you get to 240, that's when you are going to start having problems. The fact that the temps come back down once you get moving tells me you don't have enough air flow at slow speeds. You already have a shroud. So you only have the fan to pull more air. I don't think a better fan is going to bring you down 15 to 25 degrees.

I'll be curious to find out the radiator you have. Even though you have an air flow problem, your high temps can be resolved by adding volume to your system. ie; a bigger radiator.

 

[Biggredd2069]

I've only owned the car about a year. Have done a lot of maintenance and upgrades to get it "running right". Nothing changed per se but I added fuel injection, new water pump and some other necessities. I had some light smoke coming out of my heater vent when I was idling at that temp and seemed to be ready to go higher on temp. I'd prefer to avoid buying a radiator as the issue has only happened on very hot days. Want to just check the cooling basics first. I can always avoid going through a drive through but never know when you might get stuck.

 

[Ccas]

I understand about hoping it's something small but sometimes chasing gremlins ends up costing more money, time and aggravation.

Any way to talk to the previous owner about temps? I can't tell you how many guys with fuel injection additions all of a sudden have overheating issues when they didn't previously. That way you can eliminate the fuel injection unit as a possible source.

The smoke coming out of the heater vent could be steam from a bad heater core. If your system can't pressurize from even the tiniest crack or leak , you will run the types of numbers.

 

[ayilar]

Something similar happened to me on my '70 'vert (318, non-AC, 19" radiator -- yes, it is small but that's not the issue).

After I bought the car in March 2018, I had the water pump/timing chain replaced and the original radiator recored. All new hoses, new thermostat. Generally ran warm but not hot for the first 15 months, EXCEPT that the temp needle would reach the upper (i.e., RHS) end of the "safe range" when in stop-and-go traffic or idling for more than a few minutes in hot weather. I was not worried as temps would drop back down once the car started moving. Then, my car overheated at highway speeds on the way back from Carlisle this past July and I had to limp back home (drive 10 miles then cool for 15-20, you see the fun).

I thought the original 4-blade no-shroud fan was the issue. I replaced it with a 6-blade shroud fan from a formal Fury (it fit right in, with minor inserts added to anchor the fan without messing the original radiator). I replaced the t-stat for good measure. The engine felt smooth, but it was still overheating AND one could see bubbles in the coolant when running the engine with the radiator cap off. One top-end rebuild and a thorough cleaning later, the car is once again great. Temps are at the very bottom (LHS) of the normal range and, in 95 degree weather stop and go, did not even reach the middle of the range.

Short story: the main issue was the head gasket PLUS the fact that a lot of carbon buildup (probably from lots of small trips made by the first two owners in the first 15 years of the car's life, as @cbarge ventured) started getting loose and clogging the cooling. Hope you are luckier than I was. I again love my car.

 

[Biggredd2069]

It is tough chasing gremlins. But hard to just replace the whole thing cost wise for a very occasional problem that hasn't become a full blown issue yet. I only drive it once a week so I have some more testing I need to do.

 

[Knebel]

Whats your timing and AFR at idle? Are you letting fitech control timing? If so, have you synced and phased it correctly?

 

[rkrochen]

It is tough chasing gremlins. But hard to just replace the whole thing cost wise for a very occasional problem that hasn't become a full blown issue yet. I only drive it once a week so I have some more testing I need to do.

Go back to the basics. These cars needed regular maintenance which is something we have gone away from in this day and age. This includes a regular or yearly flush of the cooling system, new thermostat, new rad cap and new antifreeze. Do this first and see what happens, it should be done anyways. Sometimes we overthink or over analyze things.
Good luck hope this gets resolved easily.

 

[Welder guy]

Well you spent the cash on a FiTech EFI system that will operate an electric fan. You might as well install One . I did and I’ve never looked back. It solved all of my heating issues. It’s easily removed to put back to stock in the future if so desired as long as you keep every part you remove. Check out this thread Anyone got a favorite electric fan kit for C-body radiators?

 

[odcics2]

Had an issue like that back in the day. Turned out that "Bars Leak" actually bars the flow over time.
I pulled the rad and had it boiled out. Turns out that the Bars Leak had accumulated in the core.
After it was boiled and rodded out, no more problem.

 

[John Kirby]

I used to have this issue, my 66 New Yorker would slowly overheat when at low speeds. Ultimately replaced the radiator with a 3 core unit and an electric fan. It came with a two speed controller. Starts up when the temp gets to 180 or so. As the heat builds it switches on a second winding in the fan motor and sounds like a jet turbine. I have a 30002 Fitech too and it has a digital readout of engine temperature. Doesn't go over 210 when sitting at idle while I am tinkering with it. I don't have the fitech controlling the temp, the controller that came with it has a sensor you stick between the fins.

The head gasket issue mentioned is worth investigating. No point spending on radiator and fan if that is the real problem. If you see any bubbling when the engine has warmed up with the radiator cap off that is a telltale sign you have a head gasket going bad. I doubt that is the real problem though. These radiators are ancient and probably have had several doses of Bars stop leak over the years. Using it once is probably ok, but over time and several applications the flow gets restricted as odcis2 noted. No point in paying for a recore when you can buy a new aluminum one for less then 200 bucks. I bought mine from a guy at Carlisle a while back. The company is named Rainbow Products out of Mt Ulla, NC. 704-278-0054. Has the electric fan setup too. The fan did cost extra. It draws a quite a bit of current, that original alternator and wiring probably isn't up to the task. I installed a 100Amp one-wire unit and a heavier wire for it (0 Ga). The skinny wire Chrysler installed won't work very well and the firewall connection will probably burn out. So I had to replace that connection and the battery feed and bypass the firewall connector. The charging system on my car is modified a bit to handle the electric fan as well as a 500 watt amp for the stereo. (A MB.Quart NA540.6 six chan amp. Makes your ears bleed if you really crank it up) I would stick to a new two core unit if using the original fan, there isn't a lot of room with a 3 core.

 

[John Kirby]

One last thing, timing, I was attempting to use the fitech for timing with the stock chrysler electronic distributor. I did have overheating issues and went back to the stock box on the firewall. Didn't run very well. Kept misiring and hard to start. Fitech recommends getting a HEI style distributor (expensive) so I will play with that when the finances allow it. So if you tried the same thing that could be an issue. Mine runs very well without the computer control so it's not a major issue.
As I think about it I did replace the timing chain back in the mid 80's and it did help with overheating too.

 

[FURYGT]

22" or 26" radiator? What thermostat do you have and is it a heavy duty one with a relief valve/opening? Clutch fan? A/C water pump or non-A/C water pump? Big blocks with 22" radiators can have a tendency to get hot at idle in my experience.

If this happens again either turn the heat with the fan on and/or put the car in neutral and raise the RPM's a little bit to get the water pump and fan turning faster.

 

[stubs300]

Few questions to help us determine what's going on and help you solve your issue.
What radiator are you running....old, new, recored?
Do you have a shroud?
Also what kind of fan....4, 5, 6, 7, blade?
Solid fixed fan or clutched?
What temp termostat?

I'll ad to that, When was the last time the system was serviced/flushed? Over 2 years ago? Then it's past time to geturdun!

I've only owned the car about a year. Have done a lot of maintenance and upgrades to get it "running right". Nothing changed per se but I added fuel injection, new water pump and some other necessities. I'd prefer to avoid buying a radiator as the issue has only happened on very hot days. Want to just check the cooling basics first. I can always avoid going through a drive through but never know when you might get stuck.

So you replaced the H2O pump but you didn't inspect the radiator or truly flush the cooling system, is that correct? If so, then you have another issue being that your rad has a clog and won't allow it to do it's job. Sounds like it's time to do a super flush!
Why is it people neglect the snot out of their cooling system, and then when things go south they have no clue as to what's happening. Let alone not wanting to correctly correct the problem. I just don't get it?