720 .... Overheating connected to heater fan controls?

[ProJect]

Hi!

 

First of all thank u guys for helping me get my fusible link figured out and giving me a ton of knowledge about it.

 

My issue is that after replacing the link I'm still experiencing periodic overheating.

 

While driving it started to overheat. I turned on the fan and hot air and when I turned on the fan the dash lights flickered. Then the temps went down for a good while. When it overheated again I turned the fan off, causing the dash lights to flicker again and the temps went down.

 

So I'm guessing it's something between a bad connection at the fan controls, but I'm not sure how they would be connected. My other guesses are a bad thermostat or bad hearing pump.

 

Anyone have an issue like this?

[datzenmike]

What is this for?? the the 510 or the 720????

 

 

 

The heater does not control the engine temperatures. It's strictly for warming the cabin.

 

Normal engine temperature readings, I have found, are at or a needle width above half way on the marked run range on the gauge. So where is yours when this happens?

 

As the temperature and the gas gauges are run from the same supply, does the gas gauge also rise when the temperature gauge rises???? 

 

Possibly a thermostat as it does directly control the minimum engine temperature but a bad water pump bearing will only make noise.

[ProJect]

It's the 720. The gas gauge doesn't move, just the heat. It almost seems like my turn signals are triggering the issue too. I checked my fuses in the cabin I'm going to check under the hood, too. Such a weird gremlin issue. My thermostat is about a year old, but maybe my fusible link issue or the last bad alternator damaged it?

 

Thanks again for the knowledge.

[ProJect]

My temp gauge typically sits right above the cool line. It went all the way towards hot when I pulled it over and cool down to make my way home.

[datzenmike]

It should run in or near the middle. Was this a $2.99 special thermostat from WallMart? If $8-$10 brand name it might be inferred that the thermostat is maybe ok and it's the gauge that's off.

 

As to the fusible link what did you end up doing? was there a problem with it? was it replaced?

[thisismatt]

Running the heater can certainly affect engine temperature...

[ProJect]

For sure, that's why I turned it on because it was creeping up. The thing is, sometimes it'll be fine for a while with it on, sometimes with it off.

 

The thermostat was a decent one. It ran the same way on the old one. One thing is I have to keep my coolant just a little low because it spills out the heater core. Still trying to find a replacement one.

[thisismatt]

How low? Maybe the pump is sucking air?

[datzenmike]

1 hour ago, thisismatt said:

Running the heater can certainly affect engine temperature...

 

....yes, you are correct but it doesn't cause over heating.

[datzenmike]

1 hour ago, ProJect said:

. One thing is I have to keep my coolant just a little low because it spills out the heater core. Still trying to find a replacement one.

 

This is a red marker.  Thermostat was the first one but this is much stronger. I imagine it over heats often so either this is a repeat or one too many times is starting to blow the head gasket.

[weldingrod]

Did you test the thermostat before installing? I got caught that way once, brand new out of the box thermostat was faulty. Test it by putting it in a pot of water on the stove and heating it up. Should open before the water starts boiling. If you have a wine making thermometer you can check the temperature of the water when it starts to open.

 

[jagman]

Mike, Your advice to me was to check the fan.  That turned out to eliminate my 720 overheating problem.

[datzenmike]

The clutch fan on the water pump.

 

Solving is a process of elimination. There's mention of adjusting the heater controls causing the dash lights to flicker.... maybe the gauge is just reading wrong? Now the heater leaks so could have been low on water.

[datzenmike]

8 hours ago, ProJect said:

For sure, that's why I turned it on because it was creeping up. The thing is, sometimes it'll be fine for a while with it on, sometimes with it off.

 

The thermostat was a decent one. It ran the same way on the old one. One thing is I have to keep my coolant just a little low because it spills out the heater core. Still trying to find a replacement one.

 

You can't run low coolant to prevent leaking somewhere else. That's asking for trouble. If core is leaking shut off water to and from it and get a new heater. You can join the two hoses under the hood to by pass the core BUT make sure there is no flow, seal with a wooden dowel or something.

[ProJect]

I hadn't seen it overheat until I was having issues with that fusible link, so it's only overheated in the last two years a couple times and I shut it down when it reached the top market before H. The coolant doesn't look hazy, it's there any other way I can check for head gasket damage?

 

While I ran it today the dash lights were flickering and the heating problem seems intermittent even when it's just sitting there. The blower fan was also cutting in & out.

 

I'll connect and seal the hoses to the heater core and get a new thermostat in the meantime.

[datzenmike]

Sounds like loose fusible link connection. Wiggle them and see if dash lights flicker. Wiggle the headlight switch.

 

On 11/2/2021 at 8:36 PM, datzenmike said:

 

 

As to the fusible link what did you end up doing? was there a problem with it? was it replaced?

 

Is there a good ground from battery cable or the block to the body sheet metal??????

[Stoffregen Motorsports]

On 11/2/2021 at 8:52 PM, thisismatt said:

Running the heater can certainly affect engine temperature...

Right, it's a second radiator. If the engine is running hot, turning the heater and fan blower on will definitely help cool it down.

 

Don't keep driving it until you figure out the problem. It could be fatal if not caught soon enough.

[ProJect]

datzenmike I was able to find another fusible link for sale brand new.

 

Made sure to get a decent Napa thermostat and I'll give it a test before putting it in.

 

Just running for diagnostics for right now, not going to drive it until I have it figured out.

 

I swapped terminal junction and connected everything.  It ran decent and then the dash lights, turn signals, and cabin fan all stopped working! The temp and gas gauge both turned off, too.  I tried moving the fan switches and nothing.  Turn signals and nothing.  Then they just turned back on...

 

I just got a read on my hose diameter and I'll be just getting a dowel and plugging both sides to keep it simple.  I do think it'll be good to do, but I think my main problem is still something electrical.

 

Any relays I could check?  What kinds of fuses do I have under the hood and where are they?

[datzenmike]

All fuses are in the cab, left side on the kick panel under the dash near the hood pull release. It's not a blown fuse as it would remain off if blown. This seems to be a loose connection.

 

1/ Dash lights, turn signals are on two different fusible links BUT they are on the same stalk on the left of the steering column. Did you flush with contact cleaner? It's a spray can with a straw. Don't use carburetor or brake cleaner it might melt plastic. Might be better to remove the turn signal/headlight switch for proper cleaning.

 

2/ Heater fan.... next time it stops working honk the horn or try the 4 way flashers. If either work then not the power from the battery. Next try the radio if it's working then maybe the relay. If also not working then possibly the ignition switch* or the Green fusible link.

 

3/ Temperature and gas gauges are powered from the ignition switch*. or the Green fusible link.

 

* 2/ and 3/ both have the ignition switch in common. The ignition switch also gets it's power from the Green fusible link that is paired with the Black fusible link. If it's making intermittent contact it would explain 2/ and 3/. Put a test lamp on the end of the green fusible link farthest from the battery and wiggle the link. See if the test light goes out. Fusible links can look fine but are burnt under the insulation.