3F Overheating Help (1 Viewer)

[Letsgocamping]

I’m at a total loss and could some help.

I’m experiencing intermittent overheating, only at highway speeds and under load. As soon as I see the needle start to rise, I take my foot off the accelerator, drop into neutral, and pull to the side of the road, and the temp normalizes within 30sec.

No issues driving on normal streets.

There’s no obvious coolant leaks. Radiator is full (and was vacuum purged and pressure tested). Thermostat and water pump are new OEM parts (and t-stat was tested prior to install according to FSM). Oil is clean. Heater pumps out hot air.

I feel like I’m missing something here. Read through all the overheating threads I could find and haven’t come across a similar issue or solution. Anyone have experience with an issue like this?

 

[coldtaco]

Replaced clutch fan fluid with thicker viscosity fluid? New fan clutch? Sometimes coolant temp readings failures are due to a bad ground I think associated with the instrument cluster

 

[Letsgocamping]

Replaced clutch fan fluid with thicker viscosity fluid? New fan clutch? Sometimes coolant temp readings failures are due to a bad ground I think associated with the instrument cluster

Now that you say it, electrical/sensor issues is something I hadn’t considered. Some of the wiring under the hood is pretty janky. I’ll have to look in that direction. Thank you

 

[Houser]

I’m at a total loss and could some help.

I’m experiencing intermittent overheating, only at highway speeds and under load. As soon as I see the needle start to rise, I take my foot off the accelerator, drop into neutral, and pull to the side of the road, and the temp normalizes within 30sec.

No issues driving on normal streets.

There’s no obvious coolant leaks. Radiator is full (and was vacuum purged and pressure tested). Thermostat and water pump are new OEM parts (and t-stat was tested prior to install according to FSM). Oil is clean. Heater pumps out hot air.

I feel like I’m missing something here. Read through all the overheating threads I could find and haven’t come across a similar issue or solution. Anyone have experience with an issue like this?

Is this rig new to you or have you been driving it for quite a while without any issue until just now. I am asking because often when these cruisers are freshly imported their cooling systems have been pumped full of stop leak to make them smell better at auction. Mine was that way all the hoses had to be replace because they were lined with a crunchy layer of stop leak. When I squeezed the hoses I could hear and feel the stop leak crunching loose.
Quite the mess getting all that stuff flushed out of the block and radiator. That is likely why many new old cruiser owners end having to replace their radiators. I was able to get mine cleaned out and am still running it without any issues.

 

[Letsgocamping]

Is this rig new to you or have you been driving it for quite a while without any issue until just now. I am asking because often when these cruisers are freshly imported their cooling systems have been pumped full of stop leak to make them smell better at auction. Mine was that way all the hoses had to be replace because they were lined with a crunchy layer of stop leak. When I squeezed the hoses I could hear and feel the stop leak crunching loose.
Quite the mess getting all that stuff flushed out of the block and radiator. That is likely why many new old cruiser owners end having to replace their radiators. I was able to get mine cleaned out and am still running it without any issues.

I’ve had it a while. One of the first things I did was a total cooling system refresh, including replacing the 30 year old hoses, swap in a new radiator, new fan, etc. I haven’t had this issue from it until more recently.

 

[Letsgocamping]

Well, I decided to flush and refill the coolant. Back flushing the heater core kicked out a lot of sediment. After refilling, burping out the air, and testing, it’s made some huge improvements. I’m going to keep driving and monitoring temps, but if anyone out there is scratching their heads at weird overheating issues, give the system a flush.