tr7triumph.com

79 Convertible - Notice the overflow container was 'low' added almost 3 quarts of fluid bringing the level of the overflow container up to about 2 inches from the radiator cap. Took the car out for about a 35 mile ride through the countryside. Next day after everything cooled down, I checked the overflow container and it was low again. Bottom of the radiator indicates seepage - no streams. Pressure tested the system , pumped up to the 16 pounds shown on the radiator cap. Checked back after 10 minutes and the pressure had dropped almost 1 pound, down to almost 15. There was no visible leak - just the seepage at the bottom four or five rows on the right (passenger) side.

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I think what you are calling the overflow container is actually the header tank. If so mine was always very low, & operated there.

However I found the cooling was marginal at best in our tropical sun. I had a couple of old Toyota Cressidas which have a rectangular over flow re-breathing tank, just the right size to fit between the radiator & the inner guard. With one of these fitted the header tank is always full to the very top. Even with the air conditioning at full blast in our summer, my gauge never goes more than a needle witch above quarter.

Hasbeen

Hello mmi16,
i suppose the thermostat may be faillure. If it doesn't open the engine
becomes to hot and the tank pressure cap opens.
Or the cooling lines inside the radiator are blocked due rust
Please check if the bottom hose of the radiator is getting warm or hot
as the top hose when the engine is warm.
The expansion tank should be half full as the repair manual reads.
I hope it helps.

Greetings
Roger27TBB

Roger27TBB wrote:Hello mmi16,
i suppose the thermostat may be faillure. If it doesn't open the engine
becomes to hot and the tank pressure cap opens.
Or the cooling lines inside the radiator are blocked due rust
Please check if the bottom hose of the radiator is getting warm or hot
as the top hose when the engine is warm.
The expansion tank should be half full as the repair manual reads.
I hope it helps.

Greetings
Roger27TBB

Thermostat is working fine. Temp gauge holds steady midway between the 1/4 mark and the 1/2 mark. Both hoses indicate normal water flow. I think at age 44 the radiator has started to meet its end date.

Looks like the rad needs to be recored at your local radiator shop. Re: cooling: If the rad is (partially) blocked, it will have a hard time cooling the motor. A blocked rad can be cleaned (best to get it professionally cleaned at that point). A core in the heater can become blocked as well, in standard form the flow is constantly going through it (heat is cut out by flap in heater alone). In A/C cars the flow to the heater is actually shut off.

Thermostats are design to fail in open position (failure to get heat to the heater core). That's what the spring is for. When the thermostat failed in my Integra, I could get zero heat in the cabin even though it was above freezing. I knew exactly what it was even though that's the first time it happened to me (ever). With that design, the engine can't overheat due to a failed thermostat (safety design).

The cooling system will slowly lose coolant with use. The difference between when it's too high (expels out the overflow tube when hot) and too low, low coolant light turns on if you have it (only newer ones) isn't very much. The coolant level is meant to be checked periodically (like when you check oil level) but as people never did that (how do you open the hood?) they put the light in there to warn you (sometimes a PITA but a good failsafe).

In a properly operating cooling system, the needle won't move from 1/4 from cool running to traffic jam hot driving, more than a needle's width as Hasbeen says.

New Radiator installed from TWS Motors



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Another view
[img]https://scontent-iad3-1.xx.fbcdn.net/v/t39.30808-6/379186622_6796529387064999_1020987862113744660_n.jpg?_nc_cat=101&ccb=1-7&_nc_sid=4c1e7d&_nc_ohc=2DNoRg49xBMAX9VduAW&_nc_oc=AQloyPVHQtU5xbM6igrPWKz6IMYYCw0dfaZtNv90P7o_tRayq_oXInBusHCAJinv8m-nt1zW-KBhjsttXZ-4-eQ0&_nc_ht=scontent-iad3-1.xx&oh=00_AfALk-FjUtqYDSc-CdZ897IxPbvy0XgwuziCGTz90103Xg&oe=6508CE00
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Another point on the cooling of the TR7 engine. The proper thermostat has what I call the "Triumph foot". It is an extension that blocks off the flow to the engine in the activated (warmed up engine). This allows the full flow to the radiator. Without it, part of the coolant goes to the radiator and part to the engine regardless of temperature so at best you only get partial cooling. Make sure some PO hasn't replaced it with the wrong one. Parts suppliers can send you the wrong one (happened to me) and (some) don't seem to know that this is crucial.

That’s a nice looking alloy rad with quality welding. Need to source something similar for my v8 conversion.