The Triumph Dolomite Club - Discussion Forum

This is a follow on to the discussion started in Kyle's indicator switch thread that got WAY off topic!

This will no doubt be coloured by my own rabid ravings and opinions but first a History lesson.

In the beginning cars had enormous radiators which reached way above the tops of their engines.

They had to be huge because until the 30s at least and often later, engines didn't have water pumps and cooling was entirely dependant on the thermic syphon, not very efficient!

So the water pump revolutionized cooling, followed by the viscous fan, but the whole thing was still a bit of a pigs breakfast because you were still wasting up to 6% of your engine's power driving a fan that was only needed when the car was stationary.

Enter the electric fan with thermostatic control switch (Sadly too late for Dolomite production) which stops the power wastage and gives much better temperature control than a viscous fan or anything earlier.

Now, we have modern systems with electronically controlled EVERYTHING for maximium efficiency as Rafe described in Kyle's thread, but i'm not really concerned with those as trying to get that sort of control onto a Dolomite is probably a step too far for anyone but a total electronics freak!

Because there is a second side to this debate, in that the engine works best and most efficiently when its HOT and I don't mean warm, I mean near boiling temperatures. It's why cooling systems are pressurized, to allow the engine to run at temperatures above 100 degrees centigrade WITHOUT boiling over.

And herein lies the dilemma, you need the engine hot to run efficiently but if it gets TOO hot it will boil, so there's a very narrow window when everything is bang on correct. Older cooling systems such as ours were a compromise between thermal efficiency and risk because, even in England, ambient temperatures can vary by over 40 degrees C and this makes it harder (or too easy at the other extreme) for the cooling system to do it's job.

Now add in the paranoia exhibited by most Sprint owners where one tiny twitch in that guage needle can have them running to the shops for a new rad or water pump and you have a situation where most of these cars are actually overcooled, especially once an electric, thermostatically controlled fan is deployed. Because old habits die hard! Most of us old school guys are used to a cooling system which is designed with a lot of "wriggle room" in it, to allow for unseasonal weather and other ambient conditions, because control was so poor. Add an electric fan and control is much better, but us paranoids still don't like to see that neeedle climb over the halfway mark, to us it means something is about to go bang and we don't like it!

But let's look at the situation in more detail, firstly, what does that big N in the middle signify? Well "Normal" of course, but what actually IS normal? The answer is (assuming everything is working correctly - a long chance I know!) somewhere around 87-88 degrees C. A slant engine's winter thermostat is 88 degrees so that's the theoretical optimum operating temperature, but it isn't really! What it IS, is a compromise dictated by the lack of control inherent in that design of cooling system. 88 degrees is not much more than lukewarm in engine terms, the best efficiency is almost 10 degrees higher, but running at 98 is too risky so the manufacturers lower the bar to stop too many overheating complaints when unusually warm weather hits and upsets their equations.

Now look, briefly, at the Vauxhall motor I have in my Toledo. It's not a generation ahead of the Triumph slant, it was first introduced in 1980 so was probably in design in the mid 70s. Yet it has a 92 degree thermostat (all year round) probably because it was designed from the outset to run with an electric fan. And that 92 degrees would be getting unpleasantly close to the 3/4 mark on a Triumph guage!

So what I am really saying here, is that there is overheating - and then there is our PERCEPTION of overheating, which is not the same thing at all! I have recently fitted a thermostatic switch to the electric fan on the Carledo (pure laziness, I ran with a manual switch for a couple of YEARS, just because there was no obvious place for an automatic one and I couldn't be arsed to buy a hose mount) Knowing the high stat opening temp, I had to opt for a fan switch that deploys the fan at a whopping 98 degrees and cuts out at 93 and do you know what? It's absolutely perfectly fine! And the automatic sender doesn't deploy the fan anywhere NEAR as often as old nervous Nellie here used to do it manually!

It's my contention that you could employ a similar high opening stat and thermo switch on a electric fan equipped Sprint lump and suffer no ill effects therefrom. You'd just have to get used to the "new normal"! Which might take a while!

Steve

As a quick incidental, when I fit a thermostatic switch (in the TOP hose naturally) I always fit it so the switch is at the lowest point of the hose (ie, with the wiring tags facing downwards) which allows the sender to be under water, even if there is a little air pocket lodged in the system, seemples!

Steve

A great post, reasoned and well explained. Thanks.

It is not a great design, the seal between the head on the inlet manifold is a real pain to seal, the daft pump location, the lack of a header tank. Of course one of the major issues for both the Stag and the Sprint was clueless owners and mechanics in the 70's not putting the proper coolant in. Putting water into an alloy head is very good way of killing it. The system fills up with silt, so even if the blown head gasket is fixed, the compromised cooling system is going to fail again.

You are right that running an engine too cool is a bad idea. Increase fuel consumption, having to run rich and potentially more engine wear.

As for modern engines, they can run remarkable cool. I am pretty sure the M47R diesel in my 75 could run quite happily without coolant. When the thermostat broke, the temperature needle barely moved, however hard i drove it.

cleverusername wrote: ↑Fri Jul 05, 2019 11:50 pm It is not a great design, the seal between the head on the inlet manifold is a real pain to seal, the daft pump location, the lack of a header tank. Of course one of the major issues for both the Stag and the Sprint was clueless owners and mechanics in the 70's not putting the proper coolant in. Putting water into an alloy head is very good way of killing it. The system fills up with silt, so even if the blown head gasket is fixed, the compromised cooling system is going to fail again.

You are right that running an engine too cool is a bad idea. Increase fuel consumption, having to run rich and potentially more engine wear.

As for modern engines, they can run remarkable cool. I am pretty sure the M47R diesel in my 75 could run quite happily without coolant. When the thermostat broke, the temperature needle barely moved, however hard i drove it.

I regularly drive a Zafira Diesel and though the temp in the summer does get up to just a gnats dick over normal it's never boiled. Then a couple of weeks ago I had some battery trouble which meant I couldn't switch it off so I sat outside a supermarket with the engine running for half an hour whilst the owner did her shopping! Slightly bothered by the rising temp, (5/8ths and climbing slowly) i got out and looked at the fan to see if it was running. It wasn't and foolishly i put my hand in to discover it was seized solid! But even WITH the non functioning fan, the temp stopped climbing before 3/4 hot and well short of the red, and it lost no water. And once I got rolling it dropped promptly to "normal".

You're perfectly correct about the Sprint engines inherent design faults, (why do you think I use Vauxhall engines) but there ARE folk around who understand them these days and a well maintained Sprint motor is a lovely thing to drive behind and certainly shouldn't overheat "just for fun" I did the RBRR last year in Mahesh's Sprint, 2166 miles in 50hrs 1 min the engine was only off for about 2 of those 50 hours (2 breakfasts and a handful of fuel stops) It never raised a sweat and didn't use a drop of water (or oil) and the only failure we had was (surprise surprise) the dipswitch packed up about 10 miles short of John o' Groats, fortunately just as the sun was coming up on the Saturday morning. I was able to bodge it so we had dip and flash and could finish the run.

Steve

Makes a lot of sense Steve but as you say those who have suffered the dreaded head gasket issues will always be cautious. I like to see a proper temperature gauge that shows a number. Mine runs at 90 usually and creeps to 92 on a long climb. I had an intermittent electric fan issue and my own temperature got hotter than the car when I saw it move to 100...

Carledo wrote: ↑Fri Jul 05, 2019 8:29 pm It's my contention that you could employ a similar high opening stat and thermo switch on a electric fan equipped Sprint lump and suffer no ill effects therefrom. You'd just have to get used to the "new normal"! Which might take a while!

Steve

I totally agree. When driving on "the other side on the scale" towing caravans in the Italian Dolomites at 36 degrees outside temp I have seen my Dolomite run very cool as the temp needle was going the next round up towards hot...

When all is healthy running a new normal temp will have no side effects and I think will be better for a dolomite engine.

Modern engines have still the fluctuating temp figures. When I worked at Vencer developing a new sportscar we programmed the temp gauge steady normal from 60 degrees to 110 degrees and after that the gauge would rise again. When you stop a modern hot engine and start again after a minute the temp has also risen but cannot be seen on the gauge like you can see beautifully on the old capilairy types. Probably all car manufacturers do it this way as "modern" cars are within a few km's on operating temp and then the needle never moves again when reaching horizontal or vertical.

Just to avoid to have drivers unneccesary nervous when temp fluctuates.

Jeroen

Interesting thoughts. Some experiences of mine to share that relate more to stopping than what happens when actually running.

When I first started racing what was then a standard Sprint, the lack of feedback from the engine very soon had me install a temperature gauge that displayed actual temperatures. Racing in the heat of an NZ summer and I would often see temperatures of 110-115 degree C. Absolutely fine as the car wasn’t boiling. BUT, with standard water pump, standard Sprint radiator and an electric fan, slowing down or stopping left so much heat in the engine that continued to heat the coolant which in turn couldn’t be dissipated by the radiator and fan alone fast enough. I was then left with an engine that was boiling in the pits!

It was a slow learning process but over the years installing a larger aluminium radiator, a Davies Craig EWP (that ran on until the engine cooled) and increasing the coolant capacity (by 50%) with a header tank in the place where the washer reservoir is, all led to a car that could be raced with coolant temperature always in the 90s and stopped without incident time and time again. The EWP controller would allow the running temperature to be set. so I usually had it around 85-90. Probably I could have gone higher?

My standard road Sprint is just that, with the exception of an electric 12” radiator fan controlled by a Revotec unit in the top hose. Fan only comes on in slow traffic etc as supposed to when set up correctly. BUT, I live at the top of a hill where the road twists and turns, rising 160m over 3km so by the time I turn off at home, the fan is usually on and the temperature up 10 degrees! I’ve wired the fan so it can continue to run after the ignition is off to avoid the otherwise inevitable continued rise in temperature and localized boiling in the block.

While I agree that running the engine at a higher temperature than specified for the Sprint might be marginally more efficient, the BL design has too little safety margin, especially compared to today’s modern designs, so making it impractical to change the setups we each have found to be the best compromise for our individual and current use.

However, everyone’s circumstances are different, so many answers are of course the correct one.

And yes I agree with Jeroen, my Jag's temp gauge never moves from the midpoint on the gauge!

Geoff

Feel that I should add my post here seen as it's actually a little more relevant! This was more about sensor locations but I was interested in changes in cooling system design in more recent times.

Did some research, avoiding internet forums where there appears to be an age old debate of top or bottom with valid reasons given for both locations but with no actual scientific backup to various claims.

Doing a library search at work I've come up with quite a lot of interesting current day thinking on cooling systems. This is probably not news to anyone with a modern car but as my newest vehicle is a 1998 truck that stopped being made because it was too basic and rough for modern markets, I'm a bit out of touch. I'm probably going to absolutely bore the pants of anyone reading further but I felt it was interesting enough to share, honest, not because I wasted an hour of my life rifling through research papers and publications and you'll damn well better pretend this is good s##t.

Current thinking is to keep the coolant within the range of 85°C to 110°C, this can be achieved with a mapped electronically controlled cooling system. This allows for the regulation of temperature depending on engine speed, load and throttle position. For example for maximum performance at part throttle a higher temperature is sought after in the 95 to 110°C range though at full throttle that drops to 85 to 95°C.

This precise temperature regulation is achieved with electronically controlled thermostat, dual speed fans and finally getting to the relevant point, measuring sensors in both the engine outlet and the radiator outlet. The ECU reads the temperature, engine load and throttle position and compares this to a stored map and adjusts the fan speed and thermostat to match.

One interesting side effect of this electronic control and wide temperature changes is the interior heating can be affected by large temperature change, so the design also calls for an electronically controlled water valve for the heater so as to maintain a set heat setting.

My system is wrong, I do need to have a sensor in the bottom as well as the top hose to be able to correctly regulate the fans to maintain a set temperature, the only thing is that it will be a compromise temperature, pretty much the same point arrived at as what the engine designers came up with 50 years ago. I'll probably still have to pop the bonnet open after a fast run when hitting a long traffic queue when it's hot out to give the poor old thing a bit more breath, and with the added bonus of the classic whiff of evaporating petrol vapour from the carbs.

Carledo wrote: ↑Sat Jul 06, 2019 12:20 am

You're perfectly correct about the Sprint engines inherent design faults, (why do you think I use Vauxhall engines) but there ARE folk around who understand them these days and a well maintained Sprint motor is a lovely thing to drive behind and certainly shouldn't overheat "just for fun" I did the RBRR last year in Mahesh's Sprint, 2166 miles in 50hrs 1 min the engine was only off for about 2 of those 50 hours (2 breakfasts and a handful of fuel stops) It never raised a sweat and didn't use a drop of water (or oil) and the only failure we had was (surprise surprise) the dipswitch packed up about 10 miles short of John o' Groats, fortunately just as the sun was coming up on the Saturday morning. I was able to bodge it so we had dip and flash and could finish the run.

Steve

To be fair to Triumph I read somewhere that the water pump is in the block to allow Saab to use it in front wheel drive configuration. If they had run it off the timing chain, the water pump would have been inaccessible in a Saab. Of course I don't know if that is true or not.

cleverusername wrote: ↑Sat Jul 06, 2019 10:16 am
To be fair to Triumph I read somewhere that the water pump is in the block to allow Saab to use it in front wheel drive configuration. If they had run it off the timing chain, the water pump would have been inaccessible in a Saab. Of course I don't know if that is true or not.

Complete urban myth i'm afraid! I had a 1975 Saab 99 2.0, the first follow up to the "pure" Triumph design. It still had the slant and the jackshaft driven off the timing chain, but the water pump was driven off the fanbelt! Saab couldn't wait to get rid of that useless bit of duff design either! It also "lost" the stupid angled head studs in favour of vertical ones, had a double row timing chain and the tensioner was identical to a Sprint one (I know, I replaced mine WITH a Sprint one, it was half the price of a Saab one and in those days the Sprint ones were still made by Renolds, not poxy Rolon!) This is the engine that the 99 Turbo was based on (mine only had a single Stromberg carb) and i've often wondered if it would be possible to turn the 99 Turbo engine round, bolt a Sprint sump to the bottom and drop it in a Dolomite! The Turbo plumbing would be a nightmare but otherwise............

Unfortunately, I can't find anyone willing to lend me a decent 99 Turbo engine to try out my theory!

Steve

Kyle's thread has wandered way off topic indeed .

Carledo wrote: ↑Fri Jul 05, 2019 8:29 pm Now look, briefly, at the Vauxhall motor I have in my Toledo. It's not a generation ahead of the Triumph slant, it was first introduced in 1980 so was probably in design in the mid 70s. Yet it has a 92 degree thermostat (all year round) probably because it was designed from the outset to run with an electric fan. And that 92 degrees would be getting unpleasantly close to the 3/4 mark on a Triumph guage!

Dolomites (as in the 1972 model with an 1854cc engine) had an 88 degree thermostat for all year round.


Running an 88 degree thermostat in a slant four gives a halfway gauge reading all year round
(and a heater that produces heat during the winter!).




Ian.

Not sure that the water pump location thing is an urban myth, it's mentioned in plenty of print references that the original brief to Ricardo was that the water pump needed to be clear of the bulkhead due to the "novel" SAAB engine alignment.

Here's my tale of a hot engine, reinforcing Steve's comment about engines liking it hot as long it doesn't boil. My MGB GTV8 conversion has a capillary temp gauge marked in degrees F. I have the twin fans come on at about 195 F (90 C). The gauge will often reach 220 F (104 C) before the fans start to make a difference.

A couple of years ago we got stopped in rural France in a traffic jam with the shade temperature about 37 C. The car sat with the fans running and I watched the needle climb past the final reading (230 F or 110 C) and start to inhabit the oil pressure half of the gauge. By the time we got moving again I would guess the measured temp was around 245 F (118 C). With 4-Life coolant and a 15 psi cap it was never going to boil and in fact it idled sweetly with no sign of a problem. But then it is fuel injected.

The biggest problem was Catherine and I sitting in the GT. We were seriously overheated. Oh, for air con.

Anyone know the origins of this radiator, came with a new project I picked up this week. The owner thinks it may have been a SprintSpares race spec rad. Looks very well made.



I'm current running the Saab rad in may car with a cheapo electric fan and it works great. Last Friday night was my daughters prom & the Sprint was called into duty. It was a hot evening down South, high 20s, cuing to get into the drop off area the temp gauge was inbetween half & 3 quarters, the fan could not bring the temp down to cut out. I am also using Evans waterless coolant. Didn't boil so all was OK. I wonder if this larger rad would work any better?