Bradjones7105 Posted July 27, 2021 Share Posted July 27, 2021 Iv just built my 2500s up, done 1500 miles so far, tuned up properly on the rolling road and running great, while cruising it's sits from 1/4 to 1/2 depending how hot a day it is, but I can't go through McDonald's drive through on a hot day with it getting into the 3/4 mark, gets there in about 5 to 10 mins, I turn it off befor it goes higher, iv tried everything in the cooling system so far, only change to the engine is a tr6 ph2 cam shaft, nothing els has change, never did it befor the rebuild, rad is a fast flow upgrade that is about 3 years old, as said runs and drives great, but in traffic it get hot? Any ideas guys and gals Quote Link to comment Share on other sites More sharing options...
RobPearce Posted July 27, 2021 Share Posted July 27, 2021 What fan do you have? If the temperature stays low (and if the gauge is operating properly, 1/4 is definitely LOW) on the move then the bulk of the cooling system is probably in good nick, but if it gets hot in traffic it suggests the idle air flow is lacking. The 'S' would originally have had a viscous coupled fan, which should work well but they can fail with total fluid loss, resulting in a fan that doesn't spin and no cooling in traffic. They can also suffer bearing failure and impact the radiator, which is not good. The one on my old 'S' did that so I removed it and fitted an electric one, from a scrap Maestro. That one seized up, but I didn't even notice for quite a few weeks, until I got stuck in a huge traffic jam on the A46. The cooling system is more than adequate as long as there's air flow. Quote Link to comment Share on other sites More sharing options...
Bradjones7105 Posted July 27, 2021 Author Share Posted July 27, 2021 Has a viscous fan fitted, that seems to be working fine, it was fitted new about 2 years back, definitely spins on idle Quote Link to comment Share on other sites More sharing options...
Clive Posted July 28, 2021 Share Posted July 28, 2021 Beware being overcautious (if that isn't an oxymoron). Really you need to know what the actual temperature is getting to as gauges and sensors can vary wildly. My mkIV spitfire, the car runs in warm weather bang on te middle, cool weather a tad below. the fan kicks in at 95 degrees, off at 90. And the 95 equates to just under 3/4 on the gauge. This is with an 88 thermostat fitted. I was out in my mk3 last night. 82 degree thermostat, yet that sits in just over 1/4. When I stopped in traffic, like yours, the gauge climbs rapidly to 3/4 when the fan kicks in. This fan switch is again 95on/90 off. Yet the gauges read quite differently. Both rads are new and all in god condition. The electric fans cool the cars down to cut off (90) in a minute or 2. What I am saying is you need to know if it really is a problem. There is a lot of unfounded worry with temperatures, after all the coolant won't boil until approx 120 degrees (50% antifreeze, 13psi cap) Quote Link to comment Share on other sites More sharing options...
RobPearce Posted July 28, 2021 Share Posted July 28, 2021 Clive makes a good point. There's nothing wrong with the gauge reaching 3/4 - try just leaving it be and see whether it climbs through the red and produces steam. Also, are you suffering any coolant loss? If no to both those, there's nothing at all to worry about. Modern cars have deliberately dishonest gauges that sit bang in the middle across a wide range of temperature. This is to avoid panicking the driver, but it does mean most people these days have been trained to expect that and get unnecessarily worried by a classic's simple linear(ish) gauge. Quote Link to comment Share on other sites More sharing options...
Bradjones7105 Posted July 28, 2021 Author Share Posted July 28, 2021 My concern is that the gauge would rise higher than the 3/4 if I left it, I brought a temperature gun and took readings on the top hose and thermostat houseing, it does seem to correlate correctly with the gauge, I think I'll remove the rad and get it tested, just strange as it never did this befor the rebuild, I thought about an electric ran set up, but with the viscous fan, it's always spinning to keep the engine cooling, where as with electric fan i fear it could rise even faster as there will be no air drawn through the rad, until the actual fan kicks in Quote Link to comment Share on other sites More sharing options...
RobPearce Posted July 28, 2021 Share Posted July 28, 2021 I really wouldn't take the radiator out! There's nothing to indicate a problem with it. What temperature does your gun suggest the top hose reaches when it's at 3/4 on the gauge? My GT6 goes beyond 3/4 quite quickly in heavy traffic then stops just short of the red mark. The only time it's ever overheated in the 30 years and five RBRRs I've owned it was when the fan belt snapped. During the rebuild, did you clean up the waterways? It's not impossible that the gauge now reads higher because the head itself is cooler - more of the heat is getting to the sender. That definitely happened with my 'S' when I changed the engine (to one that actually had waterways rather than solid lumps of rust). Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted July 28, 2021 Share Posted July 28, 2021 15 hours ago, Bradjones7105 said: tuned up properly on the rolling road and running great To be honest I'd just double double double check that it's not running very lean or too far advanced at tick-over but correct at full chat. That would give you a pretty good reason for the engine temp rising in traffic/low RPM. Quote Link to comment Share on other sites More sharing options...
PeteStupps Posted July 28, 2021 Share Posted July 28, 2021 Hello Brad, not much useful to add but I also suffered higher temps after a rebuild - this manifested as chronic fuel vaporization where there was no hint of problem before. My theory was that new rings and possibly new cam were that much tighter that there was more heat from friction than before. Certainly the engine was harder to turn over by hand with the plugs out than pre rebuild. Possibly nonsense but that was the best I could come up with! Pete Quote Link to comment Share on other sites More sharing options...
TimW Posted July 28, 2021 Share Posted July 28, 2021 As said above if it doesn't smell hot, doesn't chuck out any coolant and doesn't boil then there's little to worry about especially if your digital thermostat isn't reading above about 110deg Quote Link to comment Share on other sites More sharing options...
shenderson Posted July 28, 2021 Share Posted July 28, 2021 54 minutes ago, yorkshire_spam said: To be honest I'd just double double double check that it's not running very lean or too far advanced at tick-over but correct at full chat. That would give you a pretty good reason for the engine temp rising in traffic/low RPM. ...and beware if the rubber element between the inner and outer parts of the crank pulley degrades, the two parts can rotate relative to each other. If that happens, the timing marks will move. When everything is in order, the temp gauges have always been stable at 1/2 on all my Triumphs over the years. An electric fan shouldn't cause a problem, as long as it's big enough for the job. Quote Link to comment Share on other sites More sharing options...
Tim Bancroft Posted July 31, 2021 Share Posted July 31, 2021 Def agree with above., are you absolutely sure the car is as hot as the gauge states. Old wiring..resistance etc. I have replaced the electric temp gauges in my GT6 and 2.5 with Racetech mechanical gauges, they seem more accurate. However, whilst the GT6 has got hot, she has never boiled over. Without being snotty, why visit a MacDonalds drive thru..asking for trouble! 🤣🤣 Quote Link to comment Share on other sites More sharing options...
Bradjones7105 Posted July 31, 2021 Author Share Posted July 31, 2021 I was hungry 😂 going to get the rad checked and wire an after market gauge up to it Quote Link to comment Share on other sites More sharing options...
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