Stag Overheating

[alpenmac]

How many of us have been told, at the various shows that we have attended, that the Stag was always prone to overheating? I always say that, in my ownership (7 years), my Stag (1973 MOD), has never overheated - famous last words!
What is the definitive answer to the question as to why this bad reputation has been earned? Was it:
a. Bad design of the waterways?
b. Bad positioning of the waterpump?
c. British Leyland's poor quality control?
d. Something else.
e. A combination of all of the above

I would love to be able to print up some sort of definitive explanation and pass on to the "knowledgeable" fans who often tell me of their - or their friends' - bad experiences. Judging by the number of times I have been asked in the past, I reckon I would have to print up a considerable number of handouts!

[DJT]

As someone who has driven and maintained my own Stags for over 100,000 miles in 30 years, I have some insight into this. I would say it is C. BL poor quality control.

Poor quality control resulted in many engines built without ensuring the waterways were clear of casting sand. This reduced the water flow in the passages, with some ending up in the radiator. Result: overheating, head gaskets failing, heads warping. Dealers didn't see that many Stags so, when one came in for warranty work, the heads were removed, new gaskets fitted and sent out again, without curing the basic fault of blocked waterways in block and radiator. Result: repeat failure, engine replaced hopefully under warranty. Replacement engine may have been good, or may not.

I have knowledge of a Dolomite Sprint that had this problem. Original engine had head gasket replaced twice. Engine also replaced twice. Still overheated until a new owner (who bought it cheaply) noticed that the bottom half of the radiator was cold. New radiator led to normal operating temperatures and the car was still running cool 30 years later.

[tonyh]

Do Stags Overheat?

There is a lot of talk about Stags overheating, well they do if something is wrong with the engine or cooling system. There are lots of so called updates to cure the overheating Stag, most just to hide a problem that rears it ugly head later. Back in the early 80's a guy came into the garage with a header tank set up, he told me it cured all of his overheating problems, I asked him what else he had done, he told me he had the engine rebuilt, I asked him if he had fitted the header tank before the engine was rebuilt, he said no, I asked him could it be the engine rebuild that had cured his overheating problems, he picked up his header tank and left.

The standard expansion bottle works fine, but if you have a small water leak in the system it will not work as intended, when the engine warms up the water expands, pushing expanded water into the expansion tank, when the engine cools down and contracts it gets sucked back into the radiator, the smallest leak will not allow this to happen, so the fist thing to do is pressure test the cooling system to check for any leaks and check the pressure cap.

Radiators are another problem, the standard original radiators are just about good enough for UK weather conditions, some modern cores are not, I have had several customers complain about newly reconditioned radiators. If the Stag runs hot in heavy traffic and motorway speed but cools down when travelling at a steady 40mph then the modern core fitted is not doing its job. I sat down with my radiator reconditioning company back in the late 70's to come up with a more efficient core, it is about 20% more efficient than the original standard core.

Now the engine, there are many things that can cause overheating, incorrect thermostat, incorrect water pump cover, small leak on a head gasket, engine tune, piston pickup. Early Stags used a standard thermostat found on many other cars, later MK1 onwards used a thermostat with a bypass closing plate, if this thermostat is not used water will not flow correctly through the inlet manifold, if you change from a 6v water pump to a 12v pump you must change the cover or water flow is greatly reduced, in everyday use there is no difference in performance between the pumps, and small leak on a head gasket will cause localised hot spots. If the engine has overheated badly at any time there is a good chance that a piston has picked up in the bore distorting the piston and scuffing the side of the piston, it's normally just one piston, but that's enough to cause that piston to run hot causing localised hot spot, if you have tried everything else the only way to find this is to strip the engine and examine the pistons. If the engine is not tuned correctly this can also cause overheating, so check ignition timing, carb balance and mixture is correct.

The short answer is yes the Stag will overheat, as will any engine, but only if there is something wrong. I drove Stags as an everyday car for over 30 years and had to be recovered three times, MK1 Stag, voltage regulator went down, taking out electronic ignition and lots of bulbs, MK2 manual tore out the clutch plate centre, probably my fault and lastly automatic Stag transmission failed.

[alpenmac]

Taken from the above comments, by truly knowledgeable persons, do you think that the summary below should satisfy the the "doubting thomas'" that still consider the Stag to be an unreliable car?

Poor quality control resulted in many engines being built up by British Leyland without ensuring the waterways were clear of casting sand. This reduced the water flow in the passages, with some ending up in the radiator. Result: overheating, head gaskets failing, heads warping. Dealers didn't see that many Stags so, when one came in for warranty work, the heads were removed, new gaskets fitted and sent out again, without curing the basic fault of blocked waterways in the block and the radiator. Result: repeat failure, engine replaced hopefully under warranty. Replacement engine may have been good, or may not.

Even some Dolomite Sprints had this problem. Original engines had the head gasket replaced, sometimes twice. Engines were also replaced. Later, owners noticed that the bottom half of the radiator was cold. New radiators led to normal operating temperatures.

All such problems, after 40 odd years, should now have been resolved on the many Stags that are enjoyed today

[StagJonno]

Sounds fancied - might make some flyers up to give out at shows. If we get enough out there, then perhaps more folk will want to buy one

[dasadrew]

It seems that all of the discussions on Stag cooling go - (rightly or wrongly?) - to the cooling system which no doubt has it's insufficiencies in terms of design and quality.

What strikes me on the Stag is that, when opening the bonnet after a spirited run, it's like opening the door to a blast furnace. I only know two other V8's to compare - Ferrari and Aston Martin - and their inherent engine heat is nowhere near that of the Stag.

Now, of course, it should be that the cooling system takes care of the heat and maybe it's just because the Ferrari and Aston's cooling systems are better. However, I imagine that some of our learned Stag brotherhood must have some time looked into the inherent Stag engine heat? Definitely not my field of expertise, but could, for example, under-dimensioned main bearings or big ends or whatever be causing so much heat that any cooling system would be at its limits to cope? I notice that the temperature increases marginally but reliably when going up an incline. On a motorway, I've observed this by keeping the same speed, same gear, same revs and on the same day. This seems to take away the argument hat the fan / airflow is a primary cause. Has anyone looked at the problem from this aspect? Maybe trying a different oil? Maybe one of those Moly-Slip additives? Am I talking B00ll0cks?

Drew

[alpenmac]

You are not surely advocating for a louvred bonnet are you Drew?

[dasadrew]

You are not surely advocating for a louvred bonnet are you Drew?

That would be a worse crime than making a Venetian blind!

[Ritchie6]

What strikes me on the Stag is that, when opening the bonnet after a spirited run, it's like opening the door to a blast furnace. I only know two other V8's to compare - Ferrari and Aston Martin - and their inherent engine heat is nowhere near that of the Stag.



Drew

Whenever I come back from a run of say 100 miles or so I always leave the car ticking over for a couple of minutes or so before switching it off after putting it away in the garage. My thinking being that it may help the engine cool down a little by keeping the coolant flowing round to avoid possible hot spots. Am I wasting my time or does anyone think it's a worthwhile exercise??

Richard

[JeffW]

It seems that all of the discussions on Stag cooling go - (rightly or wrongly?) - to the cooling system which no doubt has it's insufficiencies in terms of design and quality.

What strikes me on the Stag is that, when opening the bonnet after a spirited run, it's like opening the door to a blast furnace. I only know two other V8's to compare - Ferrari and Aston Martin - and their inherent engine heat is nowhere near that of the Stag.

Now, of course, it should be that the cooling system takes care of the heat and maybe it's just because the Ferrari and Aston's cooling systems are better. However, I imagine that some of our learned Stag brotherhood must have some time looked into the inherent Stag engine heat? Definitely not my field of expertise, but could, for example, under-dimensioned main bearings or big ends or whatever be causing so much heat that any cooling system would be at its limits to cope? I notice that the temperature increases marginally but reliably when going up an incline. On a motorway, I've observed this by keeping the same speed, same gear, same revs and on the same day. This seems to take away the argument hat the fan / airflow is a primary cause. Has anyone looked at the problem from this aspect? Maybe trying a different oil? Maybe one of those Moly-Slip additives? Am I talking B00ll0cks?

Drew

Hi Drew

I installed this for cooling purposes (and I love a gadget) but I wonder if it also acts to move heat away from the engine compartment? I don't recall seeing any noticeable difference in my Temp gauge when going up an incline and can't honestly say I found under the bonnet to be excessively hot after a run, but I didn't do a before and after comparison on that, only a before and after of the Temp gauge (which shows the engine runs cooler with this installed).

http://www.ldpart.co.uk/shop/shop.ph...3&sid=sidd6fb2

No connection to Peter, but I do love buying from him!

Jeff

[dasadrew]

Ritchie6 That is (or was) normal recommended practice for turbos back in the days when "turbo" meant something

[dasadrew]

Hi Drew

I installed this for cooling purposes (and I love a gadget) but I wonder if it also acts to move heat away from the engine compartment? I don't recall seeing any noticeable difference in my Temp gauge when going up an incline and can't honestly say I found under the bonnet to be excessively hot after a run, but I didn't do a before and after comparison on that, only a before and after of the Temp gauge (which shows the engine runs cooler with this installed).

http://www.ldpart.co.uk/shop/shop.ph...3&sid=sidd6fb2

No connection to Peter, but I do love buying from him!

Jeff

.... and did it work?

[JeffW]

.... and did it work?

yes.....

only a before and after of the Temp gauge (which shows the engine runs cooler with this installed).

But I should also say a year later I installed tonyh 's genius thermostat that has a 30% wider opening and the Temp went down further!

Jeff

[davidf]

I saw a string of interesting posts from someone who used to be on here called down-the-plughole (or something like that). Unfortunately, his writing style was very confrontational and contentious, but some of his content was very interesting.
One of his comments was about the amount of power consumed by the valve gear and cam drive, due to the strength of the valve springs. He suggested that a useful modification would be to identify some suitable valves with lighter weight (thinner heads and stems, which would obviously require new valve guides). Then you could fit lighter valve springs, and reduce the power consumption in driving them.
I think he suggested that 15bhp was being absorbed driving the valves. I don't know how reliable that estimate is, but that power is all turning into waste heat - about 11Kw. If you could halve that, it would be a significant reduction (as well as reducing wear in the chains and sprockets).
I suspect the existing valves were limited by the technology of the time, but I understand that valves in modern engines are a lot lighter.

[Ritchie6]

Ritchie6 That is (or was) normal recommended practice for turbos back in the days when "turbo" meant something

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

Richard