TR2/3/3A TR3 Sudden Temp Jump

[Perrymip]

Driving at speed I noticed a quite sudden climb of about ten degrees in temperature. The temperature returned to normal as I coasted to a stop an idled. I found a few oily drops floating in the neck of the radiator and some oily residue inside the radiator cap. So, my first thought was of a head gasket or (shudder) a cracked head. One puzzle that I don't understand at all, though: the oil drops and residue in the radiator are black; the engine's oil is fresh and amber. Is there anything else I might check before removing the head?

 

[deadair]

It might also be a rusted-through freeze plug. I'm a little rusty (yuck, yuck) on the location of the freeze plugs in my TR3, but I experienced the same problem with an old Toyota, where a freeze plug in the head had rusted through.

 

[TFR]

What I found is when the engine gets hot the water level is reduced by it being pushed out the overflow tube. A lot of TR3 owners install a catch bottle so when the car cools down the water is "sucked" back into the radiator. When this happens serveral times the an air pocket develops. When the air pockets is at the sensor position the sensor gets hot very quickly. Then when you stop the water is forced forward thus cooling off the sensor.
Anyway I am having temp issues because of the 95 degree heat in my area so I added an electric fan and a catch bottle. Thinking of putting on a TR4 fan.

 

[Geo Hahn]

...Anyway I am having temp issues because of the 95 degree heat in my area so I added an electric fan and a catch bottle. Thinking of putting on a TR4 fan.

You can add a catch bottle and it will catch but likely won't throw back (like a dog) unless you modify the radiator cap or get a cap suited to that purpose.

I, too, think 'air' when there is a sudden temo gauge change. Before removing the head I would certainly do a compression test or better yet a leak down test (cheap leak down tester can be had at Harbor Freight).

 

[TFR]

I build race motorcycle engines and am pretty much an expert at leak down and lose of power. Unless you know the original leak down values it is difficult to determine whether your engine has a problem. There can be leaks through the head gasket, valves, cylinder... All engines have leak down. ALL! But determining the source is much more deficult.

As I said in the previous post it is the water being pushed out of the radiator during the drive. Unless you catch the water and then allow the radiator to retieve it when cooling you will always have issues.
A Friend who also owns a TR3 said if you have the fuel mix correct and the timing correct you will have heat issues. Since I build race enigines I agree to a point. The correct mix and timeing will help keep the engine cool but if you have a cooling issue that pushers water out you will always have cooling issues. The solution is to catch and replenish.
I just added a TR6 fan and I think this will help my engine stay cool. I added the 15 blade fan but modifying the mount and moving the radiator back a slight amount. So fa so good.

 

[Geo Hahn]

...As I said in the previous post it is the water being pushed out of the radiator during the drive. Unless you catch the water and then allow the radiator to retieve it when cooling you will always have issues...

I my experience that big neck on the TR3 radiator is an effective expansion tank and a recovery/return system isn't really needed if everything else is working right.

I fill the neck so there is about a 1/4" of coolant in the bottom -- anything more than that and it will just puke as it warms up. The 'puking' merely takes the coolant level down to where it should be -- I don't think it introduces any air into the system.

 

[TFR]

It really depends on how hot the engine runs whether it pukes out too much water. I'm really speaking from experience on this. I just experienced the same issue and it stopped when I added the catch bottle.

 

[Perrymip]

I appreciate the commentary above. But I'm dealing with some sudden, unexpected change on a car that has run pretty consistently, with the usual ups and downs, for 200,000 miles, although, of course, with all the normal TR3 heating issues along the way.

What's especially odd to me is that I was traveling at highway speed when the temperature rise occurred. I didn't experience any corresponding loss of power, so nothing broke. And at that speed the mere airflow would be enough to keep the temperature steady, under normal circumstances. And, most surprising, when I slowed and left the engine running, the temperature went back to normal. So, the moment when TRs commonly give problems--at idle, and after speed--everything reverted to normal, for as long as I sat there.

It was the oil drops (although tiny and few) in the radiator that made me think of the head gasket or worse.