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wayne taylor

Bleeding cooling system

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OK. Just had an alternator conversion and narrow belt conversion done at the same time. Very very pleased with everything. Also fitted a new water pump.

 

Except when I drive it, the temp gauge is now registering almost maximum temp!!!!

 

No leaks.. but when the engine has been running hot for a while I noticed that the two hoses going into / out off the thermostat housing "appear" NOT to have any water in them??? With the rad cap off, the water is not swirling just stationary and squeezing the hose connecting the thermostat to the top of the rad feels like there is nothing in it.

 

I have raised the front of the car up and am happy the thermostat housing is the highest point. I have turned the heater on but still it feels like (a) no motion of water thru the system and (B) both top hoses feel like they are empty.

 

I have undone the clips holding the hoses on - there is a tiny bit of seepage but not significant.

 

How do you bleed the cooling system of a TR4 properly please?

 

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What are the symptoms of the thermostat stuck closed?

 

Could it be the voltage stabiliser for the fuel/temp gauges (even though the fuel seems to be behaving).

 

What is the best way to remove an airlock (I have a modern rad not one with a header tank).

 

[Thermostat housing is red hot . So too is the rocker box!!.

 

Why is the water in the rad - stationary? Could this suggest there is no through flow from the engine to the rad?

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If the thermostat is stuck closed it will overheat and you won't get much flow through the radiator. Incidentally, what type of thermostat do you have? Originally they were a sleeved bellows type which allows water to circulate through the bypass hose during warm up. Then when up to temperature the sleeve moves to block the bypass and allow coolant into the radiator. If you have a modern thermostat you need to fit a restrictor in the bypass hose or you won't get full flow through the radiator when the stat opens and you could run hot. As Al pointed out there's loads about this on the forum.

Edited by peejay4A

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Did you take the thermostat out when you did the water pump replacement? if so did you put it back the right way round eg with the temp sensor on the engine side.

Graham

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Graham - left the thermo in.

This evening after work I took the thermostat out and went for a spin - problem gone! Temp normal to slightly cool.

 

I have ordered a standard 82 degree thrmostat from TRGB who never mentioned restrictors in by-passes (PJ)??

They said they have been selling these for years and a standard £3.95 thermostat is fine. Unless I want the all singing all dancing double bellows original design thermostat at £48 each!!!

 

Q: Can i drive around during the summer without a thermostat - any damage done???

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What can I say. Search the forums for the story about thermostats then make your own choice. Personally I run a sleeved bellows stat and if I had a modern stat I would use a restrictor in the bypass hose.

Edited by peejay4A

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All,

 

I dunno if I am a 'benchmark' or an 'outlier', but I have a different experience of TR cooling.

 

I live in Malaysia, always 28-34C ambient, often road temperatures 40+C.

 

I have a standard TR4A, unsleeved thermostat, standard engine, dynamo, standard water pump, standard radiator/cap, standard mechanical fan (no additional fan), standard cardboard rad cowl... ign timing is normal, carbs normal (35+mpg on highway).

 

In normal driving the temp gauge stays just below half around town, slightly lower on the highway. After a long run and then hitting city standstill traffic (mid afternoon heat) the temp will rise to the top of the gauge, just hitting the red but then stabilise there. Never boils.

 

I don't see anything wrong with the design...it seems to work quite fine in this climate... never experienced airlocks & bleeding in 25 yrs of ownership..

 

I say this because in various threads there appears to be doubt over whether ar TR can ever keep itself cool without 'modern assistance'...i believe it can!!

 

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PJ: I have asked around and looked again for this restrictor issue in the bypass hose? Still none the wiser.

I spoke to another Triumph place locally and they say pretty much the same - the original one is the best BUT a modern one will do for 'most' situations.

What is the purpose of restricting flow thru the bypass hose with a modern stat then?

 

I' ll report once the new one arrives and I have driven around with it for a while.

 

CTc: Sounds like you have the perfect TR there! 35mpg: OMG! I dream of that on my TR4. I am around 25mpg on my Strombergs.[And they are recently rebuilt].

Edited by wayne taylor

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The reason for a restrictor is to ensure that all or most of the water flow is through the radiator when the stat is open.

 

 

(null)

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Before the system was disturbed, the temp was perfect, even after idling for 30 mins in sweltering heat.

 

Now - when I took the thermostat out, I noticed that the bit that was protruding forward tow ards the rad was the bit which had the fixed metal arch and the bit hidden from view tucked insde the thermstat housing was the spring loaded shank of the thermostat.

 

Now this is the idiot bit where I show my ignorance:

 

I manually opened the thermostat valve by pushing FROM the arch side of the stat back towards the thermostat housing. Isn't this against the direction of flow,?

 

I thought that when the temp of the water circulating around the cylinder head got hot enough, the stat opened thus allowing water to transfer forward from the cylinder head thru the top hose into the top of the rad????

 

This is in the opposite direction to the physical opening of the stat spring mechanism.

 

Confused?

 

What is the correct way to fit the stat. And IF the above appears to be the wrong way around - why has the temp behaved itself in the past?

 

 

OK - found the explanation, thanks: The reverse logic of how I thought a stat would work:

 

Edited by wayne taylor

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I have now received the new stat. The old one had a 3/16" hole drilled thru it with a little loose metal pin passing thru it. The new one doesn't have any holes in it. What is the hole for?

 

Later in the day, I washed the engine bay down and then went for a spin to dry it out. About 20 mins thru the drive the temp and fuel guage dropped to zero? Could that possibly be the resistor or whatever it is called which controls the current to these two guages getting wet?

 

Where is this resistor situated please?

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The voltage regulator feeding the temp and fuel gauge is in the driver's footwell, top right and it has 3 terminals, or more correctly, 2 terminals and an earth connection. Green is 12v from the fuse box and Light Green/Green is 10v regulated to the instruments.

Edited by peejay4A

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Note that the voltage regulator contains a thyristor, i.e. a diode, and is therefore "current oriented". If you went from positive mass to negative mass during the alternator conversion, you burned it. When burned, the volt reg loses its capacity to regulate and gives a 12V output. Then, both fuel and temp gauges show excessive values. Easy to check with a voltmeter.

 

Badfrog

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Badfrog: To be specific regarding your point about converting polarity:

 

Are you saying the thyristor will/would fail if subject to a polarity failure during its operation? Obviously in my instance, I removed the battery, did the bsuiness with the alternator and then reconnected the battery the other way around. Would the thyristor be affected during this 'passive' phase of polarity change?

The fuel/temp gauges behaved until I washed the engine bay. This afternoon after PJ told me about the regulator, I double checked it and then checked the feed back from the fuse box. It 'appears' there may have been a poor connection inside that very sophisticated ( :) ) fuse terminal and after some tightening up the gauges are working again. Buit Badfrog's got me wondering whether the gauges are now telling me the truth.

 

Graham (Harris): If the new stat doesn't have a hole and pin in it, should I fit it? or ask for one similar to my original? OR - drill my own hole in it (without pin).

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Alan: Looks like you are correct: The gauges are behaving themselves.

Graham: Spoke to TRGB today about the elusive hole and they said because I had the bypass hose already fitted, the holed stat was surplus to requirement and the one without a hole in it would be fine???

I shall soon see........................................

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Regarding the comment about the voltage regulator - I do not believe that the original 10v regulator/stabiliser used such a modern device as a thyristor.

It uses a bi-metal strip and sort of averages 10v (ish). The modern units may well have a thyristor.

 

However I could be wrong.

 

Roger

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I have opened a couple of the electronic regulators to see what was inside.

 

One used the common 7810 fixed voltage regulator, the other a 10V Zener and a small PNP transistor in emitter-follower mode.

 

The voltage regulator would be the better method if they had used one with a heat-sink tab. But they used the small TO92 plastic cased version and these barely take the heat involved.

Edited by AlanT

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Regarding the comment about the voltage regulator - I do not believe that the original 10v regulator/stabiliser used such a modern device as a thyristor.

It uses a bi-metal strip and sort of averages 10v (ish). The modern units may well have a thyristor.

 

However I could be wrong.

 

Roger

But you are right, semiconductor based regulators came later than the 4. The bi metal strip is not polarity sensitive (doesn't care about positive or negative earth) as remarked already. Later parts and replacement parts, although visually identical, use a semiconductor and come in two flavours: positive earth and negative earth, and definitely not interchangeable.

Mike

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