Continued overheating, coolant spewing from radiator when warming up...
 

Having a problem with overheating. 87' 7-MGE started overheating when the weather was cold 2 weeks ago, but then would cool down after driving it on the highway. Last week it started getting hot while driving on the highway and cooled down after I had to pull off to the shoulder and turn the car off. I brought it home and left it in the garage. I put coolant in it the next day and it ran perfectly.

Started it the next day and while idling and warming up the radiator light came on in the dash. The car was still relatively cold (temp gauge at about 10-20%) and I opened the radiator cap; coolant spewed out everywhere. The radiator light then turned off on the dash, however after warming up the engine then began overheating again!!!

I thought it was the thermostat, so I replaced the thermostat and it is still having the same issue!!!! Please if anyone has an idea of what it could be, respond and give me some pointers...thanks

Blown head gasket

-Search "BHG" symptoms, the rad light came on due to not having coolant in the reservoir. your loosing coolant for a reason .

OmG really? Is that the only thing it could be? Because I just had a newer engine put in it last march cause the original engine had a BHG!

have you ever checked the clutch fan to see if it was spinning right? i had some of the problems you had. like when idling my car would get hotter to the point of boiling then as soon as i move it would cool down.

Where is the clutch fan? I do have an automatic transmission... Is it the electric fan right next to the radiator fan? Cause that fan doesn't work, I have to connect it directly to the battery for it to come on...

I thought it was the fan clutch too but the car overheats on highway too. Did you replace with a used engine, re manufactured or rebuild the old one to be specific? Check the fan clutch which is silver looking thing with small fins attached behind the radiator fan and is driven by the water pump. The small electric fans are for the AC

The fan Clutch can fail in many ways.

1. Any fluid leakage means it's toast.

2. They can seize solid. That's the "sounds like an airplane".

3. They can fail to engage. Engine overheats.

4. With the clutch firmly bolted to the waterpump, any fore/aft play in the fan blades means the bearings are shot. This often happens before the bearings lock up, as in #2 above.

I replaced it with a used engine that the garage claimed had 47k miles on. They also said they had to rebuild some part of the engine, I don't remember exactly. (I've put about 12k miles on it). Ok is the fan clutch connected to the radiator fan? Cause the fan itself works fine. There is still coolant in the reservoir...

The fan should be resistant to spinning by hand to a certain degree.... more so when it is cold. The fan clutch is the aluminum hub between the water pump and the fan.

A shot fan clutch (which allows the fan to spin too freely), a clogged or restricted cooling system, a missing fan shroud or any combination thereof may cause overheating while the vehicle is sitting idle or moving at low speeds.

Do note that the MKIII's coolant sensor is logarithmic and that beyond the normal operation range the temp is either VERY cold or VERY hot... In other words, if the temp gauge presents a temp more than a couple millimeters from normal, you're quite likely running at damaging heat levels... shut the car down IMMEDIATELY!

Oh yeah I see now that the fan is resistant to me turning it by hand. It looks like the coolant is just not circulating through the engine. It just builds up in the main radiator hose like the thermostat doesn't open...

So test the thermostat.... just because it's new doesn't mean it's good. There are a number of possibilities here including advanced timing, bad water pump, coolant blockage, missing fan shroud (combined with other minor problems), bad thermostat and BHG. Start testing.