Thermostat question

decampos

decampos

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According to the book the guy had at the auto store, the new thermostat I bought is correct for my car ('75 3.0csi). Though it fits into the thermostat housing as it should, comparing the new with the old, those bottom parts are different in diameter (old one is bigger).

Do you think this is a crucial difference?

Any advice much appreciated.

thermostat.jpg
 
decampos said:
According to the book the guy had at the auto store, the new thermostat I bought is correct for my car ('75 3.0csi). Though it fits into the thermostat housing as it should, comparing the new with the old, those bottom parts are different in diameter (old one is bigger).

Do you think this is a crucial difference?

Any advice much appreciated.
Click to expand...

hi
as jerry is telling you the differences could mean a severe problem

the easyest check is the bottom part diameter, it should be big enough to close the cylindric hole that you will find in the thermostat housing

this is the hole to be closed:
150820073354.jpg



the more complex one will be the thermostat length, assuming that the old tsat that you show has been working ok, let the new one have the same length

this is the length to be checked: (in this pic one is Ok and the other is wrong (depending always on the housing))
150820073350.jpg


no autostore guy will know this for you, because he is dealing with data, and you are dealing with a 40 year old car that may have had n-owners that had brought the car to at least n-different mechanics :twisted:

good luck and do not hesitate to ask questions
 
Thanks deQuincey and 61porsche. Those are excellent replies and exactly the info I was after.

deQuincey said:
good luck and do not hesitate to ask questions
Click to expand...

I cannot figure out the problem. I'm trying to bleed the cooling system. Only steam is coming out of the bleeder hole. The radiator is not even getting warm but the water temp is almost maxing out. It's as though the thermostat isn't opening but I've eliminated a bad thermostat being the culprit.

Any ideas??
 
Well

Flow could be one problem. Water pump impeller corroded? Pull it and see.

When you put the t-stat back in drill a small hole at the top beforehand- it will bleed all by itself. You'll hear the radiator fill up and gurgle.

If there's flow from the small hose on the top left of the radiator back to the expansion tank a good steady stream should shoot across the tank. Visible by leaving the cap off if your's is metal or directly through the semi translucent plastic tank; even if you have to hold a work light against old yeller.

Pull the radiator and flush it. Not once but several times and upside down too. You're trying to get small sediment out. I've even used CLR a cleaning fluid from the grocery store. Couple of bucks. I flush mine every other year or if I'm doing something up front.

I'd pull each spark plug- if one is very clean; that's a problem with the head gasket or a crack.
 
probably the first thing to do is the spark plugs issue but tell us more:

from were are you comming to this situation ? was the car normal running before ? if so, what changes have you implemented ?

steam in the bleeding hole ? that is new for me ...

one of the bleeding procedures includes opening the cap of the water reservoir during warm up, there you will see the flow from the small hose from the radiator, and eventually bubbles also comming off

if you have a problem the water will start comming off the reservoir

then the sparks may tell such a blown gasket or a crack

if no sign is comming from the sparks then i would reccomend a complete check of the whole cooloing system including dismantle of radiator, hoses, water pump, and so on, flush, clean....etc

good luck
 
thanks for the replies chaps. I really appreciate it. There's a lot of good info there.

The car ran reasonably cool before I began tinkering with it. The temp gauge would creep up in not terribly dense traffic so I figured I'd bleed the system as it would be an easy thing to do.

Well …

The bleeder screw was utterly seized so I bought a new thermostat cover with the newer type hex head bleeder screw. While I was in there I replaced all the hoses. I've checked and double checked, they're all correct and go where they should.

When I attempt to bleed the system now, the engine gets hot, radiator remains cold, when I crack open the bleeder screw, it's just steam. The expansion tank does appear to gurgle though.

What could I have screwed up? The new thermostat cover looked fairly identical capacity wise to the old.

Any ideas??
 
Stevehose said:
Is your radiator clogged? Remove and back flush to check?
Click to expand...

It seemed to be not necessarily clogged before I began dicking around. When I drained the system, the anti-freeze looked pretty clean (I know the doesn't mean that there wasn't a build up of crud but it was a positive sign).

I'll have another look tomorrow in the cold light of day and maybe the problem will be staring me in the face.

Thanks again.
 
Iffin

the incorrect t-stat is used in the wrong housing, no flow. NADA. Measure the distance of the recess for the t-stat to the orfice. Then compare the depth of the t-stat. Or take the hoses off and look inside.

The cover doesn't matter.

Or for grins- leave the t-stat out temporarily. Fire it up and see if the radiator gets hot.
 
61porsche said:
the incorrect t-stat is used in the wrong housing, no flow. NADA. Measure the distance of the recess for the t-stat to the orfice. Then compare the depth of the t-stat. Or take the hoses off and look inside.

The cover doesn't matter.

Or for grins- leave the t-stat out temporarily. Fire it up and see if the radiator gets hot.
Click to expand...

+ 1
you mention that you changed the cover !, but if the housing remains the same you need the old type tstat

leaving the tstat out for a trial run its a good idea to check if the radiator is clogged, but i am not really sure that is a very good idea, because as i explained in the thread that mr.porsche61 linked the tsat is a double effect one, opens in the front but closes in the rear, so if you remove it ...???

because what i am missing is your deduction when problems started, the temp gauge started to go wrong, and then you decided to bleed, change the cover and the tsat...but who tells you that the failure was not there but in the:

- viscous cutch of the fan
- water pump
- belt tension
- radiator clogging
- mixture, ignition, ....running lean ?

i would check quickly the tsat, it is easy, take the old tsat and measure the total length, if it is shorter, thenwrong tsat
 
Everything is fine. At last. Used the correct thermostat (the one on the left. The middle is the old broken one, the one on the right is the wrong one that was sold to me as the correct one). It's interesting that the new one is still not the same dimensions as the original one and yet works perfectly.

Took a long time to bleed as there there were a lot of air pockets. This was a real chore as the jet of spluttering boiling anti-freeze is directed right into the fan. There's nothing like showering in coolant.

Thanks again for all the pointers. All useful stuff.

therms.jpg
 
Last edited:
Pull the small hose to the expansion tank and verify that it is streaming water when the engine is running
 
wrong thermostat!

Fun resurrecting this old thread. Was sorting out the Bavaria I just bought. The car had been in storage for many years. My driving it in ever-widening circles was the first mileage it'd seen in a long long time. It was running a bit hot, like 3/4 of the way up the gauge, so I thought I'd check/swap the thermostat. Turns out the car, which has an old-style thermostat housing (clearly stamped "72"), had a new-style thermostat in it (the one with the bent legs). No place local had one I could lay my hands on on a Saturday. Scrounged around my parts bin and found an old-style one (the one with the straight legs), tested it in a pot of boiling water, put it in, made sure the foot of it fit snugly against the housing (it does). The car is much happier now, but I wonder how long it had been running like that...
 
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