TR2/3/3A Normal vs Max acceptable coolant temperature?

[RC64]

I've been troubleshooting an overheating problem on my TR-3A and have read many of the threads on the subject. I've tried blocking the bypass with a copper plug as suggested by Geo and others. That has made a noticeable difference and I can run at about 185 on the highway but the temp still does start to climb in traffic. What I haven't seen in the discussions is a collaborative opinion on what might be a rough estimate of a maximum acceptable temp to preclude possible engine damage. In other words, at what temp should I find the a friendly watering hole where I can have a couple of beers while the system cools down.

I have several items on my list to try next, but I want to make sure I don't cause any harm when I get too far from the shop while I'm doing the testing.

Rick...

 

[CJD]

The maximum acceptable is the point at which the coolant boils, therebye negating any cooling in the engine. That temp would be 212 degrees at sea level, standard pressure, and then adjusted for the amount of antifreeze AND the pressure increase in the system. This number would be close to 230 degrees at the thermostat housing. But, that is complicated by the fact that your 50 year old Smiths gage is likely off by 10 degrees or more.

By now I think you understand why nobody gives an actual number...there is none known for your car!

My car boiled over indicating 230 on my gage. That incident gave me MY number. Until you experience a boil over (not recommended!!), you will have to guess at your number. My gage is calibrated to be accurate at 212 degrees actual. So, I now have a number...230 indicated. If I am stuck in traffic, I start turning the engine off during stops when the temp gets over 210 on the gage.

Worth mentioning, during an overheat, the gage slowly creeps up. When the temp anywhere in the engine reaches the critical temp, you get a boil over. The indication at the gage is a sudden abrupt increase in temp indication. So...creeping gage you are good. Abrupt increase...shut down immediately, and hopefully you can avoid damage.

Staying cool on the freeway, but not in traffic indicates insufficient air flow at low speeds. The TR3's, in general, suffer from this issue. If you plan to drive a lot in city traffic, an electric fan would be your best single upgrade for your time and money.

 

[Geo Hahn]

Sometime when the engine is warmed up you might use an IR gun to check the difference in temperature from the top of the radiator compared to the bottom. As I recall yu want to see a drop 10° or so.

There is a world of difference between 'getting hot' and 'overheating' but still it makes a driver nervous to see the needle moving into the upper half of the range.

 

[mrv8q]

I'm with Geo, an IR gun is your friend, just so you know the approx. real temperature. In my car, 185* degree on the guage is actually 177* on my black-painted test point. YMMV... I sure cast a doleful eye when the guage is showing 200*; at least I have a little wiggle room.

 

[TR3driver]

I've driven home with it boiling more than once, never seemed to do any harm. Even limped home a few years back with no fan belt after the water pump shaft snapped. IMO as long as you don't let it run low on (water based) coolant, the engine will be fine. But going past 230F will very likely damage the temperature gauge and possibly the thermostat.

My Dad did eventually blow his TR3A up, but IMO that was from excessive EGT and overly lean mixture, rather than from the coolant getting too hot. It was running waterless coolant (because we couldn't find any other way to keep it from boiling), so not boiling over. (But the gauge was ruined, so no idea how hot it was actually getting.)

 

[Darrell_Walker]

Not recommended, but one time my TR4A was stolen. It didn't have a water pump installed at the time. The thieves abandoned it several miles away, most likely because the steering linkage had failed (the upper rubber joint came apart, and wound up the tach or speedo cable). Towed home, installed the new water pump I was waiting on (and fixed the steering), and drove it for several years with no apparent problems!

 

[Geo Hahn]

I seem to recall John Macartney relating the story of a TR3 being delivered by road from the factory to a dealer somewhere in the UK. Upon arrival the driver was reviewing that all was well and, upon opening the cubby box, discovered that the never-installed radiator hoses were still neatly stowed in there.

These are indeed tough engines.

 

[GTP1960]

The thieves abandoned it several miles away, most likely because the steering linkage had failed

those thieves probably thought you had a very sophisticated anti-theft system in place.

 

[RC64]

Thanks to all of you for that feedback. I have a pretty good idea now of what to look for. Thus far I haven't seen any indication of any 'boil over'. Although I've pushed that upper hash mark a couple of times by the time I shut down back at the shop (before Geo's bypass plug fix), I didn't see any signs of it venting. The temp gauge was restored by the folks at Moma. Brand new tube and sensor. Besides, when it's stable on the road before starting to heat up its right at the 185 mark. I'd guess that's a good indication.

Tomorrow I'll see if I can get some good temp readings at the spots you guys pointed out. I like the black dot idea to. The readings I've tried to get off the thermostat housing have been all over the ball park.

Rick...

 

[tinman58]

After reading this post I went out and checked the temp on my TR3. The gauge reads about 220. Had me worried. Measuring the temp on the top tank 175 bottom tank about 160. Now I feel better (need gauge recalibrated)

 

[RC64]

On my original post I forgot to add a second question on the overheating. This one with regard to Geo's bypass fix that I implemented. I got to wondering about the effect on the water pump when there is little to no flow through it with the thermostat closed and the bypass essentially blocked. I added the small hole in the cap, but that's not allowing much water through. Any thoughts on the impact of no flow through the pump, and the engine?

Rick...

 

[TR3driver]

On my original post I forgot to add a second question on the overheating. This one with regard to Geo's bypass fix that I implemented. I got to wondering about the effect on the water pump when there is little to no flow through it with the thermostat closed and the bypass essentially blocked. I added the small hole in the cap, but that's not allowing much water through. Any thoughts on the impact of no flow through the pump, and the engine?

Rick...

The pump won't care, but IMO that is a Bad Thing for the engine. With no flow out to the thermostat, the water inside the cylinder head can get quite hot before the water next to the thermostat does (especially if the car is driven hard before the thermostat opens). Then when the thermostat does open, it gets a blast of hot water, causing it to open fully, and dumping cold water from the radiator into the cylinder head. The resulting thermal shock may cause the cast iron head to crack. (Although to be fair, when the TR head does crack, it's usually above the water jacket in the center where it does no real harm.)

However, it shouldn't take much of a hole to avoid that. What I did (when I tried fully blocking the bypass) was to drill a 1/4" hole through the thermostat backing plate. That way there is always some water movement, but there is no cooling lost to the bypass. The downside is that the engine takes longer to warm up, but that is rarely an issue around here. In very cold weather, it might even keep the engine from warming up at all. (One solution to that is to temporarily put something in front of the radiator to block the air flow. Many decades ago, we used to steal Denny's menus for that purpose, as they were single sheets of fairly hard plastic that fit the bill nicely.)

 

[RC64]

>> What I did (when I tried fully blocking the bypass) was to drill a 1/4" hole through the thermostat backing plate. That way there is always some water movement, but there is no cooling lost to the bypass.<<

Now that you mention I do recall seeing your suggestion about the hole in the backing plate. That sounds like a reasonable approach. I'll be pulling the thermostat out to check it shortly. As for the engine not heating up, that isn't likely for me even though I'm in the NC mountains and we do get some cold weather. I'm a fair weather driver so if I will need ear muffs I'll be riding in my Silverado instead.

When you blocked your bypass, did you have a small hole in what ever you used to block it too?

Rick...

 

[TR3driver]

When you blocked your bypass, did you have a small hole in what ever you used to block it too?

I tried it both ways. Didn't seem to make any difference either way, so I ultimately left it open.

Sometimes I really regret not having/taking a camera along. For 1/1/2000 (the infamous Y2K), the local club took a run up into the mountains, where we found some weather below freezing. I don't even have a rag top, let alone a heater, so we were more than a bit chilly. A kind person in the club loaned my daughter (who was 11 at the time) a bright red knit ski cap, which looked amusing to say the least!

 

[RC64]

Your winter in the mountains story reminded me of a similar experience shortly after I bought my TR back in 1963. A friend and I decided to venture out from DC to Syracuse up through Pennsylvania at Christmas time. Didn't bother to check the weather and ran into a blizzard. Big mistake. We had every stitch of clothing we had with us on. When I saw Don last year at a reunion he reminded me that at one point he was out walking in the snow ahead of the car to keep me on the road until we could find somewhere to pull off. I had a heater, but as you would expect it didn't do much good.

Rick...