cooling and waterpump pulley misalignment problems

tinworm · Post by **tinworm** » Sun Feb 14, 2016 12:55 pm

Hello Yves , one or two other things - you have a rebuilt engine then ? Is the timing cover the original ? I say this because you must use a 3.8 timing cover with a 3.8 water pump if you have a later 4.2 cover the recess for the pump impeller is bigger to suit the larger 4.2 pump - the 3.8 pump will fit right on ok but will not be efficient - get the tape measure out. Also - a long shot - on some engines you can fit the head gasket upside down this can blind over the coolant galleries - I do not have an XK head gasket to hand to look at - but worth bearing in mind.

Barrie

Polse7317 · Post by **Polse7317** » Sun Feb 14, 2016 2:31 pm

I have measured the recess and the impeller:

There is not a big gap between the impeller and the recess of the timing cover
For the gasket...... i can't believe a wrong side fitting... but who knows ?

PeterCrespin · Post by **PeterCrespin** » Sun Feb 14, 2016 7:30 pm

Photo of old and new thermostats?

Polse7317 · Post by **Polse7317** » Sun Feb 14, 2016 10:01 pm

here you are....

The new one has a hole on one side that the old one has not. I have tried with and without the thermostats and the coolant has boiled twice but not after the same time.

64etype · Post by **64etype** » Sun Feb 14, 2016 10:54 pm

Yves,

You mentioned that there was not an indentation or hole in the pump bearing to engage the lockscrew. Did you find a way to positively lock the bearing/shaft in position?

PeterCrespin · Post by **PeterCrespin** » Sun Feb 14, 2016 11:52 pm

Those thermostats are useless for a Series 1 E-type. Buy the correct part.

Polse7317 · Post by **Polse7317** » Mon Feb 15, 2016 6:10 am

Eric the impeller is now in the right position with the vanes touching the casing .
Peter, i bought the new thermostat from SNGB ..... there was not another one mentioned in the catalogue ? i tested both of them in boiling water and they both opened
Since my last post, i have fitted the pump on he motor and i saw something which could explain the problem (i hope so) : the hose between the above entry of the radiator and the headertank was a bit too long , and there was a bend in the middle of the 90?curve so the diameter was reduced . I'll try the motor this morning......

Post by **mgcjag** » Mon Feb 15, 2016 9:13 am

Hi Yves.....think your thermostat should be more like this.....can someone confirm please
http://www.sngbarratt.com/ProductDetail ... df6f288830

Post by **Heuer** » Mon Feb 15, 2016 11:21 am

Here is some research Marek did which you may find useful:

"The original E-Type thermostats were made by Waxstat (Western Thomson Plastics) which became part of Magal about six years ago. The opening progression is a complicated process. The thermostat starts to open as the solid wax expands with heat. The wax transitions from solid to liquid state which causes rapid expansion and then, once liquid, it continues to expand at a slower rate. If you plot out the size of the opening vs temperature you would get an "s" shaped curve which begins at the start to open temperature and flattens out and stabilizes about ten degrees later ? so a 74c stat should be fully open at about 85c. More interestingly the curve will shift depending on whether the temperature is rising or falling. So the size of the opening at any given temperature will depend on whether the engine is getting hotter or cooling off. This is hysteresis and a function of the latent heat of fusion for the wax. A consequence of having a system with high hysteresis is that there isn't a unique set point temperature but a range of possible equilibrium temperatures.

Here is the test on nine thermostats from different suppliers

a) seven out of nine were Waxstat, made in England, 2 were (quite old) West German ''Wahler'' make.
b) seven out of nine thermostats were 3.2cms high (i.e. height from mounting ring down to the closing plate) and all of them extended at least to 3.9cms
c) of the three Waxstats which did extend past 4.1cms, two of them were 3.4cms tall to start with.

The general conclusion is that a Waxstat will ''stretch'' 0.7 to 0.8cms when up to temperature. If you have one which measures at least 3.3cms high to start with, then that's good news:

Some thermostat units sit up to 4mm higher than others:

It is possible for a thermostat to never block off the bypass route, even when it has reached full operating temperature:

One solution is to machine some Delrin 2.5mm inserts which means the height the thermostat needs to reach is reduced to 38mm in order to block the bypass and route all of the water to the radiator. (Not all thermostats extend to over 40mm, so the bypass is never fully blocked off):"

Finding the correct specification of thermostat is a bit of a challenge!

Polse7317 · Post by **Polse7317** » Mon Feb 15, 2016 11:42 am

Well, it's very interesting.... thank's David , i have tested all the cooling circuit , and the coolant has boiled after 1/2 h . The only good fact is that my fan has started after +- 15 min ( the fan relay that i have now fitted works ! ) I'll try again without the thermostat to be certain that it's the pump which has a failure but i don't imagine what it is ?
By the way i'll test the two thermostats in boiling water and measure the opening aperture.

PeterCrespin · Post by **PeterCrespin** » Mon Feb 15, 2016 12:45 pm

lataud wrote:Well, it's very interesting.... thank's David , i have tested all the cooling circuit , and the coolant has boiled after 1/2 h . The only good fact is that my fan has started after +- 15 min ( the fan relay that i have now fitted works ! ) I'll try again without the thermostat to be certain that it's the pump which has a failure but i don't imagine what it is ?
By the way i'll test the two thermostats in boiling water and measure the opening aperture.

Yves, for goodness sake stop! You are not listening. Why do you care about the aperture when it is completely the wrong part????

You still do NOT understand the bypass circuit.

As soon as you leave the thermostat out you raise engine temperature because you let some coolant go via the bypass instead of the radiator. The same applies by fitting the later type thermostat. No S1 car uses the thermostat you have.

You cannot expect success with the wrong parts or leaving parts out. Just buy the correct thermostat! Then we will see if you even have a problem at all or you are just overfilling (you did not answer my question on that yet, but there is no point until you buy the thermostat Steve showed).

Polse7317 · Post by **Polse7317** » Mon Feb 15, 2016 1:00 pm

Peter , i have filled the coolant until i see it in the headertank about 5 mm above the floor. I think i have understood the thermostat function.... when the motor is cold the coolant does'nt pass in the radiator, but flows by the by-pass directly to the pump avoiding the thermostat block until the temp is high enough +- 75c? and then it opens and the coolant flows to the headertank and after in the high hose of the radiator ....and come back to the pump and after in the bottom of the motor . So the thermostat failure is when it does'nt open or not enough ( as heuer said above ) . My problem should be solved by taking out the thermostat if it does'nt open enough .

ralphr1780 · Post by **ralphr1780** » Mon Feb 15, 2016 1:09 pm

Maybe in French would be easier.
Yves, lorsque le thermostat s'ouvre, il bloque l'acc?s du circuit court et ouvre ainsi l'acc?s du liquide au radiateur. Si tu enl?ves le thermostat, le circuit court est ouvert ainsi que celui du radiateur, mais le liquide va circuler largement plus via le circuit court.

PeterCrespin · Post by **PeterCrespin** » Mon Feb 15, 2016 1:11 pm

Comme tu veux Yves. Combien de temps dois-je te dire?

Il est inutile de d?battre avec un sourd.

Polse7317 · Post by **Polse7317** » Mon Feb 15, 2016 1:12 pm

C'est exactement comme je l'entends. Donc si le thermostat est le point de blocage, je ne devrais pas avoir de surtemp?rature en l'enlevant
Je vais commander un 2 ?me thermostat comme pr?cis? ci -dessus

PS : je ne demande qu'? apprendre et comprendre....

ralphr1780 · Post by **ralphr1780** » Mon Feb 15, 2016 1:16 pm

Non Yves, si le thermostat est enlev? l'acc?s du bypass est ouvert au liquide qui n'ira donc pas vers le radiateur. Comme si le moteur ?tait encore froid.
Les 2 thermostats que tu as mis en photos ne sont pas convenables pour ce moteur. Regardes les photos de David pour bien comprendre.
Si pas clair, passes moi ton nr de t?l et je t'appellerai.

Polse7317 · Post by **Polse7317** » Mon Feb 15, 2016 1:18 pm

I think i have just understood one point ? : when the thermostat is open, it blocks in the same time the by-pass ?

PeterCrespin · Post by **PeterCrespin** » Mon Feb 15, 2016 1:22 pm

Enfin! Someone else will need to take over. I have to do my work this morning.

Post by **Heuer** » Mon Feb 15, 2016 2:14 pm

As Pete says buy the correct thermostat but be aware that even those sold as "correct" may not be to original specifications. This document from the Forum KB may help with understanding the cooling system: https://dl.dropboxusercontent.com/u/849 ... ooling.pdf and this (MG) document might be of interest: http://www.mgb-stuff.org.uk/thermostat.htm

I think this may be the correct one for you: http://www.sngbarratt.com/ProductDetail ... 4fe1be01af Do not buy one with a part number that has a * or # suffix as they are not necessarily OEM. Also suggest you contact Coventry Auto Components Ltd as they have NOS thermostats e.g. http://www.ebay.co.uk/itm/151521063427? ... rmvSB=true and http://www.ebay.co.uk/itm/131727979095? ... rmvSB=true although these examples are 86C (cold climate) versions whereas you need 70/75C.

Polse7317 · Post by **Polse7317** » Mon Feb 15, 2016 3:19 pm

I have opened the thermostat "casing" and now i understand completely how it works when it is open. Of course it blocks the by-pass with its "disc" which comes in front the slot of the by-pass
Here are the old and the new (sngb) part , on the second photo the thermostat showed by David .... they have a sort of disc (plate ?) which comes Inside when it is open and close the by-pass . Obviously my 2 therm coud'nt work as i see how is made the entry of the by-pass....

the right one :

May be I understand now why there was a failure in the engine block between two cylinders when the mechanic had rebuilt the motor. It must have over heated with such thermostat in place....

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