TR6 TR6 Overheating after being shut down

[brgrmyster]

Gents: Perhaps someone can help with a 1976 TR6 recently restored. I've had it out for two rides, during which everything is normal, including the temp (operating between the 1/4 and 1/2 slash mark on the temp gauge). However, as soon as I'm home and I turn the car off, coolant gushes to the overflow bottle (nearly fills it), and if I turn the key to all power on, the temp gauge is maxed out. After a while, after it cools, most coolant is drawn back into the radiator. What gives? I'm stumped. Many thanks gents.

Jeff

 

[Geo Hahn]

That sounds close to normal for many cars -- i.e. engines to get a lot hotter as they sit following a hot run as the coolant is no longer flowing thru the radiator and air is no longer moving thru either.

How full is the overflow bottle when the engine is cold? An over-full bottle (say more than 1/3 full) may puke when the engine gets really hot.

You might want to get some actual temps (with asn IR thermometer) to compare your experience with what others see on their 6 (gauges may not be all that accurate).

 

[DrEntropy]

Air bell in the system or a failed thermostat.

 

[Deleted member 8987]

Ahhh.....not likely if the gauge reads normal whilst driving.
Keep the coolant level in the top tank low....just above the tubes.
When cold, keep the puke bottle low, too, to give it plenty of room for expansion.

 

[SkinnedKnuckles]

That's not so unusual if you were driving fairly hard and then pretty quickly parked & shut down. A suggestion may be to drive slower the last 5 minutes from home. Yeah - could be air in the head, but usually the coolant velocity will drive it to the radiator.

 

[DrEntropy]

Ahhh.....not likely if the gauge reads normal whilst driving.

If the temp sensor is in air instead of coolant this can happen.

 

[Gliderman8]

Have you checked the temp rating on your thermostat?
Could be that a PO installed one with a higher temp rating.

 

[Deleted member 8987]

Must be one o them replacement type sender units, Doc.
Personal experience, if they're in the air, the water can be 400 degrees and the gauge will read........zero.

 

[mallard]

Sounds like air in the system to me. Make sure you keep enough fluid in the overflow so you don't run out. Let the car run up to temp a few more times and then let cool. That will purge the air from the system. If that does not work you will have to look for other problems to be discussed later.

 

[Deleted member 8987]

Yeah, one or two trips......but usually one good romp clears air out.
Heater valve on or off?
If off, and it's air back in the heater, okay, maybe. But usually, when one restores a car or does major work, they "burp" at the high point to eliminate that possibility?

 

[TexasKnucklehead]

That doesn't sound that odd to me. Mine did that until the air was out and the level in the overflow was proper. I think you need to drive it more. Why are you taking it home anyway -there's got to be another place you could be driving to?

-If you start it back up while 'pegged hot', does the gauge reading drop back down to normal in a couple minutes?

 

[DNK]

Put an aspirin in the thermostat

 

[Brosky]

Get a digital pyrometer at Sears and start taking some readings on the head at the thermostat, at the top and bottom of the radiator and on your lower hoses.

 

[Minesweeper]

Ahhh.....not likely if the gauge reads normal whilst driving.

If the temp sensor is in air instead of coolant this can happen.

Likewise, if there is an air pocket at the thermostat, the thermostat *may* not be opening at the right temp. You can run the engine up to temperature (checking temperature with the IR thermometer Brosky recommended) with the radiator cap removed. See if coolant starts to move in the radiator at the expected temperature (this may also aid in removing air from the system). Or remove the thermostat and check its operation in a pan of hot water on the stovetop. If it is working properly, consider drilling a 1/8" hole in the rim of the thermostat which should help remove air pockets and keep the thermostat bathed in liquid.

Scott

 

[Darrell_Walker]

Also check that your radiator cap is holding the rated pressure.

 

[Brosky]

Scott, I should have said it earlier, but I'm thinking air pockets. And they will move all through the system, which is why I said to get the infra red gauge. A very valuable and inexpensive tool to have these days with these or any classic car.

 

[brgrmyster]

Hee hee. You guys are not only the best, but are funny. For one, I think the radiator level may be a bit high. Cooled, the fluid is at the very base of the cap. No fins are exposed. Secondarily, air could be the culprit because I just finished a restoration, simply filling the radiator. Could be there is air in the system. I'll run it up to temp with the cap removed, see what happens. And, yes, the overflow bottle nearly puked which really alarmed me. I couldn't imagine coolant scorching a near flawless finish in th engine bay! And, yes, I haven't driven it enough. I'll try all and report back. Thanks guys.

Jeff

 

[DrEntropy]

When the thing is cold, with the nose in the air (rad filler hole as the highest point of the cooling system), the heater valve open, squeeze the lower hose repeatedly and fill the rad to cover the core until there is NO air burping from it. The T-stat will already have a hole with a bead (think snorkel) in it and allow air to rise to the highest point.

Rinse any coolant escaping with water. You can detail it after you find out what is causing the problem. I continue to think it's air bells.

 

[hondo402000]

you could take the thermostat housing off and pull the thermostat out and check to see if you have air in the head. pour coolant in the thermostat housing directly into the head, put the thermostat cover back on without the thermostat, run the car for a few minutes with out the radiator cap on and heater in full on, fill up the radiator if it goes down, shut the engine off, put the thermostat back in and cap on. it problem persist, there could be blockage somewhere,

did you have the radiator cleaned out by a professional shop?

that probably how I would approach the problem

Hondo

 

[TFB]

I have been thinking how to vent my tr3 since I am getting close to filling with coolant.I ruined a Mazda 6 engine(cracked head) failing to fully vent after thermostat change.
I didnt drill a hole in my original type stat,so have been thinking about disconnecting heater hose at valve,which will let me vent block and head and heater.Not sure if this would work on TR6.
Tom