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Stag Overheating

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    Originally posted by Ritchie6 View Post

    Still I figure it can't do any harm to leave it couple of minutes though can it?

    I was agreeing with you and the historical evidence to substantiate it!

    If you can't say something nice, don't say it !


      I am wondering if I even ought to writ this in case I am tempting fate, or sounding smug. I hope neither prove to be the case, so here goes;
      My Stag doesn't overheat. Even recently when the temperature here in Kent was 38degrees, the gauge was only marginally above its normal position, and I have checked that is reading correctly with a digital thermometer .I only have the standard fan and radiator and have made no engine, or other modifications, (Except a H.T. which is unlikely to make much difference. Or is it?). Hard driving makes very little difference either .So, why are some overheaters, and others not? It can't still be because of casting sand in the waterways. We know the cooling system is a bit feeble, but it ought to be possible to find out why some can so easily get hot, and others not. I am not convinced by the valve spring and bearing theories on a standard engine. Whoever can come up with the definitive answer would surely be made an honorary member of the Club


        Hi Mike,

        where do/did you measure the temperature and what were the results? (I have a sneaking suspicion that some Stag "overheating" is maybe a gauge overreading!)

        If you can't say something nice, don't say it !


          I agree with the furnace analogy. I don't half feel the heat coming off the engine when I open the bonnet (and I've got louvres) or the heat pushing out from under the sides of the car, yet the capillary temperature gauge always stays below 'N'. The front top hose temperature does sometimes touch 90, I have the digital pump controller set at 95 degrees otherwise the capillary gauge doesn't rise.
          Regarding running the engine on at tick over. That's one of the beauties of the ewp. The pump runs on for a few minutes to prevent hot spots.


            There is another quality defect that I have seen.

            While building a new engine in 1984 from a new short engine, 2 new heads, etc, and being busy rejecting 7 short engines because of casting sand in the blocks, my paranoia led me to a thorough inspection of all the other parts. One of the new heads had the water passage, from the rear transfer housing to the inlet manifold, blocked. Further investigation showed this to be a 'wobbly film' of aluminium across the passage, which appeared to come from the core having cracked when the casting was poured.

            I wonder how many were so affected, and what level of overheating would have come from this.
            '72 Manual O/d Saffron Yellow


              A general comment - as the original post said, so many people say 'the Stag was always prone to overheating', and there are so many criticisms of the Stag as poorly designed, referring to the engine, cooling system, etc.

              As many people have posted on here, they have Stags which are perfectly standard, 'out of the box', now well over 40 years old, often over 100k miles, and performing with no trouble.
              If the design was wrong, that could not happen; they would all fail.
              Therefore, any that have problems are in some way defective. Obviously, the core sand in the block is the favourite defect, but there are others - corrosion deposits from not using the correct corrosion inhibiting anti-freeze, etc.

              Considering that Stags have one of the highest % survival rates of any car of the period, I would say that the design was one of the best of the period, only marred by poor quality control and after-sales service.

              Having said all that, another thread I recently started, about tube fittings for the radiator plug hole, does raise the question about why the radiator expansion pipe starts way down in the right hand header.
              Does anyone know why that is?
              I have always thought it wrong, because any air or gas trapped in the cooling system will expand and drive out a lot of coolant before the gas can be released. I see from my thread that a number of others on here have made similar mods to connect the expansion bottle from the highest point.
              However, even that 'design error', it it is so, is only a problem if you have another problem, such as a leak, head gasket failure, or simply not followed the instructions on refilling the cooling system.

              I would love to know what others think.
              '72 Manual O/d Saffron Yellow


                Originally posted by dasadrew View Post

                I was agreeing with you and the historical evidence to substantiate it!

                Sorry Drew I interpreted it as mainly being beneficial to Turbo engines.



                  Heat in the engine bay is interesting- I have used a heat camera to survey the area and note that the rear top part is hottest. My electric radiator fan moves a lot of heat from the engine out under the car but it doesn’t make much difference on the temperature gauge.

                  My own analysis suggests that the Stag V8, running as designed, will cool properly but any fault, however minor, can upset the system and encourage overheating. If any bearing, main, jackshaft or cam was locally overheating there would be evidence- cooked paint, charred oil, something like that. I believe that this is the point at which the early Stag owners were let down by Triumph, who were let down by BL after a merger that, I’m sure, no-one wanted except the people in Government…

                  down_the_plughole is a sad loss. Confrontational he is, but very knowledgable about British cars of our period and he was able to impart some useful background information and down-to-earth common sense.
                  Mabel is a white 1972 Mk1½, TV8, ZF 4HP-22 auto,
                  2016 RBRR finisher. 400 mile C2C 21/22 April 2018!


                    Yes, DTPH was certainly one to call a spade a f***ing shovel
                    If you can't say something nice, don't say it !


                      when I purchased my stag (76 vintage) it had a standard rad and the gauge would rapidly climb if driven with spirit or sitting in traffic.
                      so a TH rad was collected from the man himself and fitted, an improvement but still not perfect so the kenlow that was resident had to be disturbed from its slumber in traffic.
                      when the ceramic coated headers went on the ally box supplies by stag webber (you know what I mean) was in the way of the alternator. so in went a faversham supplied ally rad and overflow tank.
                      even on a very hot day I now am more than happy that the temp gauge (capillary) only reaches normal. so rad was the fix for me. my TH rad is now happily keeping another stag in good order.
                      you pays your money and takes your choice.


                        I look at this from a slightly different perspective as I am probably one of the few nutters who has fitted the Stag engine into different cars.

                        First and foremost the engine is not the problem whether fitted with an original pump (6 or 12 vane), an electric pump or a Stagdad belt drive pump. I am assuming here that the engine is put together properly.

                        My first Stag engine was fitted to my TR which is fitted with a standard 4 row TR radiator which is the same size as a Stag radiator albeit vertical flow rather than crossflow. No engine driven fan was fitted as there was no room.
                        This fitment provided no problems with overheating whatsoever

                        My second Stag engine was fitted to my Triumph Estate (actually it was the engine out of the TR as I had built another one for that. The Estate uses a Standard MK1 PI radiator which is 3 row rather than the 2 row of the later big saloons and estates. This cools even better than the TR, but then the radiator is larger, again no crank driven fan.

                        Next I bought a Stag, and since the previous two cars were fine without the crank driven fan I removed it.

                        Oh dear! Temperature was up and down depending on load/speed/ air temperature. Since it was fitted with a late 3 row rad of indeterminate vintage I thought I would fit a 4 row rad, although this was a tubes in a row design rather than the original staggered row design.

                        How much difference did it make.......... NOTHING AT ALL.

                        It was at this point I realised airflow management was probably the key hence the fitment of a TR6 spoiler to both my Stags which stopped the temperature fluctuation problem.

                        The 3 row rad I swapped for the 4 row currently lives in my 246 bhp Stag and I have just returned last Tuesday from another 2000 mile round trip to the French alps where the air temp was generally over 30 degrees and going up twisty hairpin roads at low speed in 2nd or 3rd gear would push the temp up by 1/4 of the gauge and cause the second speed of the 2 speed Kenlowe to come on. I must admit the radiator is getting close to needing replacing as I have fed it 2 or 3 bottles of radweld over the last couple of years as the water keeps getting out!

                        A few months ago I was talking to Alan Chatterton who owns the Del Lines built Stag estate DEL 33.

                        This car uses an original outer front panel from the Estate but has Stag inner front panels with an original size Stag radiator. Alan uses this car extensively and tows a caravan about the same size as a small house.
                        He also has no overheating problems and doesn't even need a front spoiler as the air intakes in the lower front panel are about twice the size of the Stag ones.

                        Also note how Triumph mounted the saloon/Estate front number plate on brackets that hold it just below the front panel in exactly the same place as the TR6 spoiler fits.

                        If anyone can be bothered to search for pictures of Tony Harts racing Stag (the near standard one not the modsports example), you will note he fitted his number plate in exactly the same position. It is an acknowledged fact that the position of the front number plate on the Stag significantly reduces airflow through the rad.

                        To sum it all up, I reckon the real problem with the Stag engine is actually the Stag itself!

                        British Leyland could have done themselves a big favour simply by fitting the TR6 spoiler, it was in production at the same time, and as many of us know it bolts straight on. I don't suppose the lower front panel is interchangeable with the saloon models, but they could have easily modified the sizes of the holes pressed in it.

                        Makes you wonder if they knew that was part of the problem with the Stag since they did enlarge the intakes on the mk2 saloons and Estates, but I suspect that management had just lost the will to live with all the other sand related engine maladies!

                        TV8, efi, fast road cams and home built manifolds. 246bhp 220lbft torque


                          Had my stag since 94

                          Over the years I had issues with the wrong temp sender and also the earth dropping off the voltage stabiliser. no need to go into these well documented issues

                          Always a TV8, BW35 to start with. Manual O/D later. Cooling system always pressurised and always fitted with a 20lb rad cap , Always run with a Viscous fan
                          • When I first got the car it had a tendency to run hotter the faster I went (3/4 - edge of red on standard gauge), changed the incorrect footless thermostat for the correct mk2 part, helped but not a lot
                          • Fitted a Piranha P8 system to replace points setup, improved performance and smoothness but still runs hotter at speed
                          • Removed the electric fan from the front of the Rad, it was large and blanked off a fair section of the core. This further improved temp at speed
                          • Original TV8 broke main bearing caps and a new TV8 was built up, this improved running but made little difference to the temp gauge.
                          • Carbs were running a little rich but not so that the exhaust stank of petrol
                          • Changed the Rad for a HRS supplied Supergill Radiator, instant improvement in temp at lower speeds but only a marginal improvement at high speed. temp gauge at 2/3 - 3/4 rather than on the edge of the red

                          Always at stopping after a high speed run the temp gauge would rise to the edge of the red but no further. Then quickly settle down to halfway after 3-4 miles of normal town driving. After the supergill rad it would drop to 1/3 after a bit of town driving.

                          In the wintertime it would run 1/2 on motorways and 1/3 round town.

                          Then changed the failing BW35 for a Man O/d J-Type
                          Instant drop in temp at motorway speed to 5/8, just above the centre of the gauge. Yay

                          This could have been down to the much lower revs to maintain the same speed but I believe the autobox cooler under the viscous fan also contributed to hot running.

                          I fitted a "thomas tank" cooling device for no other reason than to give me a head of water above the rad top level and a warning light should the level drop.

                          Head Gasket failed on n/s even bank due to some enthusiastic motoring, maybe a little into the red sector of the tacho. This ended up with an engine rebuild 30k after the last one, 10/10 hardened crank just wasn't. Stud broke in the block and just wouldn't shift, had to be spark eroded out

                          Then came the "annus horribilus" 75 hours queueing to get into Bromley Pageant a few years back on a nice hot day. Suddenly the temp at idle started to climb, right up to the edge of the red, popped the bonnet and no heatwave, had the heater on and carried on queueing for a further 19 hours to get past the two old fossils admitting each vehicle.

                          on the traffic free journey home the temp was running 3/4 - edge of red pretty much all the time and regardless of speed!

                          Checked distributor advance was working, checked ignition timing, both fine

                          Replaced, sender, gauge, wire to gauge, voltage stabiliser, earth to stabiliser. no difference to running at speed.

                          Had to drive to le mans that week and concluded that it was a false positive - i.e. wasn't actually running hot

                          But it was, every time we stopped it spat a little coolant out of the header tank, couple of en-route strip downs of the ignition found that the Piranha p8 optic was sticky on the baseplate, loosened it a little to make it move free, helped a little initially but then temp rose again. Found that by driving at 2500rpm or less it would run at 3/4 rather than on the edge of the red. So had a slow journey down.

                          Hit Le Mans bang on rush hour, oh dear, it coped really well until well into the 2nd hour of stop start (more stop) and the cooling system spat the lot, the gauge was well into the red, alas also my temper/apathy by this point. Let it cool down and refilled. Made it to the campsite and chose to ignore the damned thing.

                          Next day curiosity led me to check various things, rad came out, back flushing it we found turkish delight type material in the inlet side, almost certainly a snake oil type product I had used on the HGF some years previous that had not appeared during the last 2 back flushes. Guaranteed to seal any HGF was the promise. Thermostat was checked, etc etc, each time it came back to the distributor baseplate.

                          Drove home 3 days later 2500rpm with no further drama, BUT taking somewhat of a ribbing from my chums.

                          At home, rad out again and found that the viscous fan had failed, oh dear, that would explain the sudden overheat at Le Mans. I believe that they offer no real cooling at out of town speeds. Carried on looking. Distributor came out, nice and original chose to swap it for a refurb unit that had lots of cheap bits attached, cap and rotor went straight back to the supplier who did accept them. (I have a world of experience or cheap ignition components and refuse to fit them). Wish I had sent the module back also as that failed within 100 miles, never mind though it is cheap, my one and only recovery home in the Stag

                          Also fitted a mechanical temp gauge, this gave me real world accurate temp readings.

                          Alas the situation (existing since Bromley) was no better at speed, temp was running at 105 c + I know that the boiling point is 130ish celcius with a 20lb cap on a sealed system but on a gauge that only goes to 110 this is not good for the nerves.

                          Fitted LD Part secret spoiler 8) and also used door seal down each side of the radiator, both helped a little but still running hot, although slightly cooler

                          Long story short I blocked the input pipe (which is half was along the top hose) to the "thomas the tank engine" header tank, making it an expansion tank and the temp dropped to 90-95c at speed. So the plumbing was allowing the water pump to draw coolant partly from the HT rather than the bottom pipe of the radiator.

                          Plan is to locate the low level sensor to the top of the rad and reinstall the original expansion bottle and be back to standard

                          I did thoroughly check the engine over after the Le Mans boil - my only boil in 25 years of ownership - and found no lasting issue.

                          There is a new issue though.... car now runs 10c hotter at 3000 rpm than it does at 2500 or 3500 rpm!

                          I use my stag to drive to Devon 200 miles motorway gives me a good chance to gather details.

                          Car running at 90c happily running at 3000rpm will start to creep up to 100c over 10 miles. It then just stays there, doesnt go any higher or lower.
                          Slow to 2500rpm and it drops quite quickly back to 90c or thereabouts
                          However run it at 3500rpm for 10-20 miles and it happily sits at 90c, 95c on a hot day 25c and above

                          When I stop at the end of a motorway journey the temp with quickly climb to 100-105c depending on ambient temp but drop quickly back to 90 once on the move again and then settle at just over 80 for round town driving - this I am happy with.

                          I am thinking the 3k rpm issue is with the refurbed distributor, vacuum advance too strong / weak, bobweights with wrong springs?

                          anyone else experienced this kind of running?

                          Stags and Range Rover Classics - I must be a loony


                            I took readings all over the place. Heads, inlet manifold etc, and the return from the radiator. I don't remember the exact figures now, but they were pretty well the same once the thermostat was fully open. The radiator return was considerably cooler. The gauge was about where I would expect it to be, having no numbers, and the thermostat was opening at the correct temperature.


                              Morning to all,
                              Ah, someone has opened the proverbial cooling can of worms again....
                              Before I go on about Stags, I remember (a very long time ago!) my 57k miles 6 year old Dolly Sprint disgraced itself by cracking a liner.
                              The car was taken to the local Triumph dealers, who frankly didn't have a clue as to the cause.
                              We removed the car from their premises.
                              Dismayed at their inability (or possibly lack of interest) to think of/investigate the cause. (They became a Peugeot dealership very soon after.)
                              My late Dad was an "instinctive" engineer and said "we are going back to basics to find the cause".
                              Timing, fuel supply pressure/"over-fuelling" all checked & ok.
                              Cooling system was back flushed, not a lot coming out.
                              Radiator was removed, hose stuck into it, lots of muck/silt eventually came out. This was in a "soft" water area
                              Suspect the (many!) previous owners hadn't bothered with any maintenance, just revving the nu*s off the poor thing!
                              As I'd only had it a couple of months I didn't want to let the car go, so a half-engine from (I believe, old age is creeping up on me!) SAH Tuning was obtained.
                              They used to do quality Stage 1/2/3 tuning kits for most Triumphs.
                              Eventually put back together, we put about 25% anti-freeze in. (West of Scotland, with winter coming on, brrr!).
                              Strongly suspect that the car probably hadn't had any anti-freeze in, as it was just a rusty soup that came out.
                              The car ran perfectly after it's major surgery.

                              The Stag.
                              Many are the stories of earlier cars having overheating problems caused by casting sand, silted up radiators, head waterways blocked by electrolytic corrosion (no anti-freeze used) etc.
                              If people were lucky, "their" dealer twigged the problems, but not all the dealers talked to one another, so if you were unlucky...…...loadsasteam and pass the new head gaskets please...
                              It appears that possibly any dealer feedback was falling on deaf ears back at "HQ". (It must have been awful working in a department where you were being inundated with complaint after complaint, all on the same subject.....maybe they all just buried their heads in the [casting] sand, and hoped it would all go away !!!

                              So, yes, think it's fair to blame Triumphs LACK of Quality Control for the majority of over-heating problems.
                              The casting sand and electrolytic corrosion issues should really never have happened.
                              I wouldn't blame the Triumph engine design/development team. As has already been pointed out several times here, look at the "survival rate" of cars with the original engine fitted.
                              After the causes of the problems became well known, remedies were found, and the engine has proved to be pretty long-lived, as long as it is maintained. (Timing chains/tensioners etc. replaced at correct mileages etc.)

                              As an aside, one of the Kent Area Members usually puts a sign in the windscreen at shows etc. This reads:- NO, it does NOT overheat !
                              Guess that pre-empts the oft-asked question ! (Nice one Keith!)

                              Whilst my car was AOK during last summer's heatwave, when I had it serviced at Faversham in November, Trevor spotted an incorrect radiator pressure cap and fitted the correct one for a Mk2. Moral of the story is to use your local specialist. There's also a good source of information here on the Forum - you only need to see how much there is on this particular subject!
                              (Although it's easy to suffer from information "overload" on the subject of cooling.....)

                              Anyway, enjoy your Stags....and the cooler weather will be with us shortly! [When we will all be grateful for a nice warm heater!]


                              '77 Tahiti Blue, Spax, MoD, poly-bushed.


                                Should have read "incorrect expansion bottle cap"...….
                                '77 Tahiti Blue, Spax, MoD, poly-bushed.