Just had the same problem with a new Motorad 180° thermo. No cooling probs whatsoever prior, but wanted the lower temp thermo in there for the summer. Drained the system, (meaning, I dumped coolant all over the truck and the garage floor), swapped the thermo and refilled. Filled through the bleeder to eliminate air pockets. Ran the truck and had good consistent flow through both hard plastic lines back into the overflow bottle (heater plate and top radiator pipe) and the heat was blasting hot. After a few minutes the temps started climbing past 200°F until eventually the fan came on at somewhere north of 210°, so I shut it down. The highest temp I ever saw in the 350 miles I've driven this truck was 207° and the fan had never come on before. The radiator was hot all across but the lower hose was cool and felt like it was about to burst from pressure. I let the truck cool and observed the coolant bottle sloshing when I squeezed the lower hose, which led me to believe that flow back through the radiator was good. The fact that the fan switch closed also tells me that the radiator flow was sufficient because the fan wouldn't have come on if the heat in the coolant couldn't transfer to the switch. I put the old thermo back in (PITFA) and refilled, rebled, etc but didn't fill the bleed screw to the top this time. Let the truck run for 20+ minutes and temps never went above 205°, turning on the heat dropped them back down to 198°, and the fan never came on. The lower hose was not hot but warm to the touch, definitely a lot warmer than before, and no intense pressure.

I brought the Motorad in the house and put it in a pot of water. At a full boil it was definitely wide open however I didn't have a thermometer to tell me when it started to open. I would guess it was much higher than 180° as there were lots of bubbles in bottom of the pot, it just wasn't yet on a rolling boil. I'm slightly suspect of my filling/bleeding method the first time around but as I understand it, air pockets prevent flow and I had good flow through the heater core and plate, as well as the rest of the plumbing so I don't think bleeding had anything to do with it. I think the fact that the Motorad did open at a full boil would have prevented the truck from actually overheating but since the lower hose had no heat at all in it that makes me think that no coolant was flowing through it as the truck approached 212°. Obviously the fan switch was seeing hot coolant, it just wasn't going any further than that into the lower hose. I guess I'll try a factory thermostat next. Because I love dumping brand new coolant all over the place.

 

Yea, and you dont really gain anything

 

Nothing wrong with the motorad. You had air and didnt let the stat do its thing.

 

There has been a known issue with Motorad stats where 198's are mislabeled as 180's. That could be his problem.

 

Is this a forum hypothetical or did motorad put out a statement?

By what he is describing its lack of letting the system cycle and air.

The lower hose being cold tells me he didnt wait long enough for the warmer coolant to open the stat. Had he waited a little, and bled more...it would have worked.

Again, send me any motorad stat and I'll run it in my truck. I bet best 4x4 could run it too without any issues.

 

I have not read anything from Motorad but when I queried Gareth at Atlantic British about the situation, and my methods, he told me this sure sounded like a faulty thermostat to him. Especially given the presence of hot coolant at the switch, but not at the thermo a few inches away. I'm also not sure why the install with a 180° thermo went past 212 at the CTS before the lower hose got warm and yet when I reinstalled the original 195° thermo it passed hot coolant long before that. Air bubbles *could* explain that however if the coolant flow was impeded then wouldn't that also prevent adequate flow to the heater core and the coolant tank or have I got that wrong? Since air rises to the top of the radiator, the presence of a strong flow through pipe 13 tells me that there was no air there, and the fact that the radiator was evenly warm eliminates poor flow through it. I'm willing to listen to any/all explanations, where would the air pockets be?

Edit: Additionally, I did nothing different with regard to bleeding the second time around. Why did the the system magically purge itself of air with the high temp thermo installed but not the low temp? Was there something specific I did wrong? I wasn't willing to let the temp climb into the 220s with the low temp thermo, and I didn't have to with the high temp version. This defies logic to me.

 

I personally had a Motorad 180 labeled stat that operated like a 198. Swapped it out with the black one from Lucky 8 and lowered my operating temps by 12 degrees.

I'm sure the motorad is fine but I bled them both the same way, I know how to bleed.

There are at least 4 different OEM/Genuine 180 degree thermostats available plus some actual OEM 198 stats... They are not all the same.

 

I'm with you Dave. This is not my first rodeo, I'm plenty familiar with cooling systems. With all that flow and hot pipes everywhere this was not a case of trapped air. The top hoses to the thermostat were hot as blazes, how come those didn't force it open sooner? I think this was a case of a thermo that opened way later than was advertised, and subsequently the fan came on while I waited for it to open which was also a first. As I said initially, it did open and the truck probably would not have overheated (as in boiled out), and Shane, you may be right that I didn't wait long enough however the higher temps required to make the system function were the opposite of my goal. This thermostat is not operating the way it was purported to.

 

 

So is it likely that motorad makes junk or is it that too many people just have cooling system issues from improper procedures?