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Spitfire Thermostat housing, help needed


Gnbickley
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Good evening gentlemen,

Following on from my success earlier today in getting my Alternator working again I decided to tackle another issue mainly the fact that the car is running cold. I've tested the dial and I'm certain it's ok. all the other dials are fine and it's getting the correct readings with a volt meter, also when I put the heater on it blows cold air.

So I removed the old thermostat housing to find that a Previous Owner had used silicone to stick it down onto the gasket and the thermostat, it was really gunked up. I also found that the two screws that had been used to secure the thermostat housing were different lengths, one being about half  an inch shorter than the other. I cleaned up the housing as much as I could and removed all the silicone and the old gasket then fitted my new thermostat, gasket and sender unit. I then put in two new 1/2 inch bolts that were the same length as the longer of the two originals and two new spring washers. The bolt on the passenger side tightened fine and the gasket squeezed out a little bit but the bolt on the drivers side gets to just about tight then there's a clunk and it comes loose again. I tightened it to the point of the clunk started the car and got coolant everywhere :(

As some of you will know from my Alternator thread I'm not much good with mechanical stuff so I'm looking for advice as follows 1. Why does the bolt clunk and then go loose? 2. How can I fix it? 3. Will I need a new gasket?

Cheers

Gary

IMAG2452.jpg

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I think you're about to become familiar with the joys of Recoil thread inserts...

Sounds like the thread is knackered for one of your bolts.  There's enough of it left for the bolt the pull down when under no load but when you try to actually pull it tight the bolt threads are just pulling through the housing ones.  Recoil thread insets come in kits with a special drill and tap.  You use the drill to remove the last of the old thread then the tap to cut a new thread.  This is obviously too big for your bolt but it's the correct size for an insert.  You wind one of these in and while it fits in the new, over-sized thread on the outside it gives you an original sized thread on the inside for your bolt to go in to.

You'll probably be OK with the same, new gasket but might want to invest in a tube of gasket sealing compound (to use in addition to the gasket) as it's a little better at filling in the corrosion in the thermostat cap than the gasket.

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Hello Gary, the bolts SHOULD be different lengths, at least they are on mine. The "drivers side" bolt hole/ tapping on the cylinder head is a blind hole while the "passenger side" is drilled right through, although not  fully tapped/ threaded. If you have a good look at the thermostat housing you can see one side of the casting is thicker than the other.

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I think a bit more clarity is needed over "the car is running cold". Is it running up to temperature and the thermostat clearly opening so the radiator gets hot? If that is happening too early, or the radiator gets warm as soon as you've started up, then the thermostat could be the culprit (stuck open). You say you've the correct voltage at the gauge - if you short out the sender does the gauge move all the way across? Worth doing to check it hasn't stuck (or way off calibration). I suggest you separate the lack of hot air from the heater from the running cold symptom - the water valves can stick, an air lock can form and the matrix can become clogged, none of which (except possibly the air lock) will make any difference to your car operating at the correct temperature.

I went through two senders and replaced the thermostat before I established there was no voltage stabiliser fitted to my car! Suddenly started reading off the scale hot one day, which caused a bit of a panic, but I quickly realised the car was actually operating normally with only the indications being adrift. The heater's packed up on my GT6, but again, the rest of the cooling system is working fine - reckon I'm one of the few GT6 drivers who needs a coat after I sealed the tunnel and bulkhead holes properly back in the summer!

Good luck with the fix - just be methodical and replace one thing at a time.

Gully

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Meant to mention too - what rating thermostat did you buy and did you check it against the one you removed by gradually heating both in a pan of water to see when they opened (and how far)? Not sure what the Spitfire ratings are, but you can get 74, 82 and 88 Celsius ones for the GT6, with the 82 being the 'normal' one for the UK.

Gully

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Yep, same ratings for the Spitfire-  warm climate, temperate climate and cold climate. 

Given the stat is on the return to the radiator, the temperature of the water going back to the engine is determined by the efficiency of the radiator. (As well as ambient temperatures and water flow and load)

Steady state conditions it works fine if everything is sized correctly - I'm not sure of the design conditions, but typically in my industry a 10'C delta T across a heater is normal - a car radiator probably less - I've read elsewhere about 5'C  

So given, the engine tends to produce more power at higher revs, the flow of water to the rad is also higher, so more heat will be dissipated and if the sizing is right, then the water will be returning back to the engine at the same temperature in all conditions. In practice it won't because there is always a lag one way or another as the thermostat takes time to open and the water takes time to get from the rad, through the engine and back to the thermostat.

But it doesn't really matter as the engine has a latitude in its operating temperature.

But what I wonder is why they have three ranges in the first place. Unless it is purely to cover the load taken by the heater in the winter. Even so 14'C is a big difference! (And the difference in the air/water heat exchange rate as the ambient increases)

 

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Just to sneak this in, if you us a look back at the parts diagram, you can clearly see, on the housing ( part number 156333) the difference in thickness between the two sides. Hence the different length of the bolts. If the thread is stripped it's no big deal putting a helicoil insert in but what I would strongly suggest that when you use the drill that you get with the kit, don't be in too much of a rush. You're drilling cast iron and it's relatively soft, so use a tap wrench to turn the drill. It's less likely to snatch and you will have far more control than if using an electric drill. The kits are very effective, take it easy and don't be frightened.

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The stat specs are related to contries climates 

82 c is std for uk and much of europe

We had to test stats for which we had a heated tank of coolant, with a serious circulator an temperature climbed in 

Tenths of a degree,  boiling like and egg is futile  

All triumpf systems need a stat witha jiggle pin to let air out when closed 

And they modulate , its not just open , it will float between open and restricted as the hot outlet gets cooled by the cooled inlet 

If you can look in the header/filler you should see the flow and ebb across the top of the rad tubes as the engine runs 

Pete

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my guys had to check these for accepting warranty so any test was approved by the suppliers.there  was a spec for how open at what temperature rise , we could measure this with a simple clip on vernier made for the job, (all were  wastats)

long time ago now any thoughts on x mm at x temp has long departed the grey matter 

Pete

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Sorry chaps to be a bit blunt but to put some direction into this - No if or buts the bolts are a different length due to the thicker shoulder on one side of the thermostat cover. A stripped thread is usually result of a past owner fitting the wrong length bolt, wrong side, and trying to tighten the cover down.  

As for the temp - Most cars of this vintage run cold in the winter and the standard approach is to replace the thermostat with the hotter running type. In this case an 88C.  Both the small four and six cylinder Standard Triumph engines have this characteristic. 

However, if the gauge is showing cold at all times of the year I would first check the temp sender. If both the temp and fuel gauges read low then check the voltage stabiliser. Finally it could be the temp gauge itself.

Sorry to be a bit heavy.

Dave   

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Gentlemen,

Firstly apologies for not responding to you all sooner, Life got in the way shortly after I posted my original post.

To clarify a few points the temp gauge rises until it reaches 1/4 then it stays put. it's been doing this since September so I'm fairly sure its nothing to do with the time of year (could be wrong though) I've checked and cleaned all the electrical connections and checked the voltage stabiliser and they all seem fine all my other gauges are working correctly as well. At the same time that the gauge stopped reading correctly the heater started blowing cold air.

I have replaced the thermostat with an 82Deg one from James Paddock and replaced the sender unit as well, again from James Paddock. I haven't had chance to find out if this has rectified the problem as the problem with the bolts has prevented me from testing them.

Going from the posts on here I think my plan will be to purchase some gasket sealing compound and a recoil thread insert kit to try and sort the bolt problem. Once I've done that I will find out if the new Thermostat and sender unit have sorted the problem or if I need to do more digging.

Mjit, thanks for telling me about the recoil thread inserts.

Derekskill, thanks for the advice on taking it easy and not being scared.

Gully, I never thought to look at the heater and temp gauge as separate problems thanks for the hint.

Everyone, thanks for taking time to respond to my request for help.

Cheers

Gary 

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The other thing I forgot to mention, the bottom of the blind hole can accumulate debris; rust, old gasket material, sealant or whatever and this can get compressed into a slug of material that effectively shortens the depth of thread. It's worth putting a tap down the thread just to clean that out. Again, remember that you're dealing with cast iron and it is a soft material, nice and easy does it!

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On 11/29/2017 at 5:12 PM, Gnbickley said:

Why does the bolt clunk and then go loose? 2. How can I fix it? 3. Will I need a new gasket?

Cheers

Gary

 

.... because you're putting too long a bolt into the blind hole - it's reaching the end of the opening and can't go any further, so it's rotating against the threads which have now stripped - hopefully only on the bolt but expect damage to both sets. The proper short bolt may yet be able to grip if you use a new one with perfect threads, and as Pete says clean the hole out thoroughly. 

As the guys have already posted, you can rethread, or else go for a S/H unit - there are plenty about.

I've nipped out to my garage in the snow (December again!!) just to see if it's feasible to drill out the bottom of this side and use a long bolt with nut instead - but it appears I have three different types; two have open-ended bolts on both sides which would allow for a long bolt and nut, whilst the third has a blind hole which ends between the two blanked-off outlets on the side face. I suspect this last is like your Spitfire version?

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  • 1 month later...

Good evening gentlemen,

 

I finally managed to get out to the Spitfire with all my new toys to try and put all your advice to effect and fix the thermostat housing to find this....(see pics)

Now I'm definitely no expert but I'm pretty sure that this crack is pretty fatal?

I've ordered a replacement pump housing along with the relevant gaskets and new bolts (just in case)

so my next question is how hard is it to replace the waterpump housing?

IMAG2577.jpg

IMAG2578.jpg

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Gary,

Dead easy! Here's a Canley diagram. I would also be thinking about changing the water pump, depends how noisy/old it is but it has to come off anyway. And, while you're at it, how about some flushing the block and radiator with the garden hose? Always worthwhile!

https://www.canleyclassics.com/triumph-spitfire-mkiv/1500-water-pump-fan

Doug

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