Started having overheating problems en route to Colorado Springs from my home in SW Oklahoma. Looked like a stuck thermostat. Engine would function fine for miles, then suddenly start to overheat. Drop down a gear or two to increase RPM and it would cool down. Had to do this several times.Had both thermostats changed in Colorado Springs. Mechanic assured me the problem was resolved.Headed back home, same problem. First leg, got about 50 miles before the overheating started. Last leg, about 150 miles before the problem started. Limped into home.Gonna take it in in a day or so, but any ideas/suggestions other than drive it off a cliff?GM

Shortly after posting this, I went to the FMCA forum and found a ton of information on this subject. Think I have enough data to look for a solution.Thanks.GM

If you have a rear radiator it is likely plugged with a combination of road dust and engine slobber tube vapor.

If more work has to be done and it hasn't been done already, change out the white plastic antifreeze expansion tank on top of the radiator. The heat of the engine destroys the plastic over time. It's easier to do in the shop than on the side of the road. Ours just happened to go bad in front of a diesel shop that happen to have one on hand in Billings, MT. I had read about them going bad and the shop said it was a known problem in the DPs with a C7.Bill

Trackrig wrote:If more work has to be done and it hasn't been done already, change out the white plastic antifreeze expansion tank on top of the radiator. The heat of the engine destroys the plastic over time. It's easier to do in the shop than on the side of the road. Ours just happened to go bad in front of a diesel shop that happen to have one on hand in Billings, MT. I had read about them going bad and the shop said it was a known problem in the DPs with a C7.BillI had mine changed out because it was spider cracking at the rear, this in it self did not cause overheating and not necessary to change unless it has signs of potential damage or leaking. I think because of the rear exposer to the sun through the rear grill, not engine heat caused this cracking as it was only on the rear. I covered the new one at the rear with metal duct tape and shows no sign of exposure or heat wear damage at present. (five years ago)

Covering the expansion tank is a good idea. I'll do it when I get back to the MH.Bill

Cat 330 Engine Overheating | Good Sam Community

jauguston
Explorer
Jul 09, 2014
The issue with the plastic expansion tank cracking has nothing to do with overheating unless it is leaking and low on water. It has a low coolant sensor that will give a warning on the dash panel.

The number one reason for overheating is a dirty radiator "if" you have a rear radiator. If you have a rear radiator and have not put a extension of 1" hose on the slobber tube back to behind the radiator you will have radiator plugging sometime soon. The fumes from the slobber tube mix with road dust and stick to the radiator fins. This is most often worse outside of the fan arc in the corners.
wolfe10
Explorer
Jul 09, 2014
Yup, I put a piece of cardboard inside the rear upper louvers when parked to keep UV light off plastic parts.
Trackrig
Explorer II
Jul 09, 2014
Covering the expansion tank is a good idea. I'll do it when I get back to the MH.

Bill
Valkyriebush
Explorer II
Jul 06, 2014
Trackrig wrote:
If more work has to be done and it hasn't been done already, change out the white plastic antifreeze expansion tank on top of the radiator. The heat of the engine destroys the plastic over time. It's easier to do in the shop than on the side of the road. Ours just happened to go bad in front of a diesel shop that happen to have one on hand in Billings, MT. I had read about them going bad and the shop said it was a known problem in the DPs with a C7.

Bill

I had mine changed out because it was spider cracking at the rear, this in it self did not cause overheating and not necessary to change unless it has signs of potential damage or leaking. I think because of the rear exposer to the sun through the rear grill, not engine heat caused this cracking as it was only on the rear. I covered the new one at the rear with metal duct tape and shows no sign of exposure or heat wear damage at present. (five years ago)
Trackrig
Explorer II
Jun 30, 2014
If more work has to be done and it hasn't been done already, change out the white plastic antifreeze expansion tank on top of the radiator. The heat of the engine destroys the plastic over time. It's easier to do in the shop than on the side of the road. Ours just happened to go bad in front of a diesel shop that happen to have one on hand in Billings, MT. I had read about them going bad and the shop said it was a known problem in the DPs with a C7.

Bill
jauguston
Explorer
Jun 30, 2014
If you have a rear radiator it is likely plugged with a combination of road dust and engine slobber tube vapor.
Grey_Mountain
Explorer
Jun 30, 2014
Shortly after posting this, I went to the FMCA forum and found a ton of information on this subject. Think I have enough data to look for a solution.

Thanks.

GM

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