Alfa Romeo Forums banner

Thermostat Housing (and coolant drain plug) Woes

4K views 22 replies 8 participants last post by  65Sprint 
#1 ·
Car was blipping past 212 on the gauge a few days ago on the drive to work, so I decided to start with a coolant flush and thermostat replacement. Workshop manual states the thermostat on manifold is to be torqued to 25.3 to 29 ft-lbs. Well I got out a torque wrench and got started and tore one of the bolts in half. It was pretty worn out so I tried a new bolt. Something still didn't feel right, and before I got to 25 ft-lbs I removed the bolt and checked the intake manifold block to find I had stripped a bit of the threads already - what am I doing wrong?

While I'm at it, is there a proper torque spec for the drain plugs on radiator and block?
 
#3 ·
Torque wrench may need to be calibrated too... hopefully you will be able to run the appropriate tap through there and save the threads...
 
#4 · (Edited)
I seldom torque bolts, especially steel into aluminum. Torquing steel nuts on steel studs is ok. Head nuts, bearing caps, flywheel, suspension, and the like is good. This is just my take after 50+ years of working on Alfa's. Tighten evenly and snug. If there is a gasket present a good firm tightening should be sufficient. Use an alternating pattern like you do on lug nuts and draw down in stages.
Cheers, Jon
 
#5 ·
Yeah, those torque values in the shop manual are just for show.... But after you have wrenched a lot you get a feel for torque in your hands. You also get a feel if something is wrong, dirty threads, cross threaded, etc. It is always wise to keep a tap and die set around to clean stuff up when needed, a properly calibrated torque wrench becomes more accurate too. Another tid bit, always back off your torque wrench when done using it..
 
#7 ·
Friends, I believe i had read something on the order of 25-30 ft-lbs. I don't have the book in front of me at the moment, but now I'm not sure, maybe it was 25-30 in-lbs. I will confirm this evening. Fortunately the damage was not excessive, it felt wrong in my hands so I didn't dare finish tightening and so the holes are not fully stripped, just one thread perhaps.

I'm always afraid when I tighten a drain plug by hand, or even the thermostat cover with the gasket I can visually see is slightly compressed, that I have not done so to the correct tightness. Is there not a great risk of the plug falling out?? Having drove a car while the wheel has blown off on the highway (those kids in auto tech never listen, hitting everything with an impact socket), I am especially cautious as I want to do the best job possible.
 
#9 ·
I don't think the problem is that you used a torque wrench, I think the problem is you used the wrong spec. IIRC it's around 10 ft-lbs.

These guys telling you not to use a torque wrench have no idea what they're talking about. If there's a spec, use a torque wrench. Just use the right spec.
 
#13 ·
I would just use a helicoil. It should be pretty easy in that location, and it'll be a lot stronger than the original aluminum so you won't have to worry as much about stripping it again.
 
#12 ·
Never seen a spec for the Alfa bleeders, but ze German car zat ze wife drives has a brake bleeder torque spec, and I sure as heck use a torque wrench to tighten them. That way I know they're properly tight and I'm not going to snap one. Doesn't add any time for me to do the job right.

I mean, you can work on your car how you want, but maybe don't give other people bad advice. People - even experienced mechanics - are REALLY BAD at judging torque by hand. I've got plenty of experience turning bolts, but if there's a published spec I use a torque wrench: to do otherwise is just to be ignorant or lazy.

If your thermostat leaks, how do you know if the bolts are loose or if the gasket is bad? Just tighten it some more, and if you strip it then the gasket was bad? LOL.
 
#15 ·
Whatever. Anyway, those numbers seem really low given that ze German car specs 6-9 ft-lb (though admittedly those are somewhat larger M10x1 bleeders.)

Steve, I'm afraid I can't find a torque spec for the thermostat for the earlier Spiders. My S4 spec's 7.4-11.8 ft-lb but it uses a different thermostat. It may be in the S3 service manual which I do not have.
 
#16 ·
Well, didn't mean to start a fight... anyway, my workshop manual (brooklands books manual) states "thermostat on manifold, 2000" should be torqued to 25.3-29 ft-lbs. If this seems high, could it be this specification is for the screw in thermostat I have heard some cars have?

Gubi, what do you do about tightening the drain plug on the block and radiator? I'm always concerned without a proper torque specification I won't tighten it enough and it will shake loose, or I will tighten too much and over years of happy ownership and frequent maintenance will do some damage.

By the way, in my workshop manual I have "Bleed screw (ATE)" specified as 1.5-2.5 ft-lbs. Between this and the two answers stated prior, this is exactly why I'm so frequently concerned over proper tightening of fasteners.
 
#17 ·
Yeah, that seems way high. I don't think the 2000 cars ever got the screw-in thermostat (that was like the 1600 cars.) It's quite possible Brooklands is wrong: do you have the Alfa service manual from Cardisc? I'd look it up for you but I don't have the S3 version.

I have never, ever removed the drain plug on the block from an Alfa Nord when changing coolant. Just can't get to it with the exhaust in place. YMMV.

I think it's got a copper crush washer? Anyway I haven't seen a spec for torque on that plug: if you decide to remove it just use a fresh washer and snug it up by feel. Alfa isn't as good as ze Germans about having a spec for everything, so if there's no spec just do your best. My wife's a Mech E and always says "tight enough is too tight" with fasteners, so I try to err on the lower torque side. I use blue loctite if I'm worried about vibration, but that probably isn't applicable for that particular bolt.

Same with the radiator, I just snug it up with a small socket. Like three fingers and pull (which is a lousy spec and why I try to use a torque wrench when I have actual numbers.)
 
#18 ·
I have the Cardisc (it's an S2!), looking through the "Shop Manuals" folder, I can't find any torque specs for the coolant system. Might be out of luck. You're right, there is a copper washer on the drain plug in block and on the radiator, probably should have replaced those... now I know better!

Getting to the drain plug is no trouble for me, with the right 22mm socket you can approach at an angle and get the thing off. I find it very easy to do with the car cool, not so much with the engine warm. Learned that the fun way. :smile2:

I'm an electrical engineer myself, I've learned to listen to the MechEs when concerned with bolt tightening. Only trouble is, I'm still having trouble believing them - let me deviate a bit to further express why I'm so concerned with torque specs! On a recent road trip (3000 miles round trip), halfway through the trip the exhaust manifold blows a gasket (cyl. 4). I check under the hood and find cylinders 3 and 4 manifold have NO NUTS on the studs! Not only that - the lower stud on cylinder 4 is GONE! I don't have any spare brass nuts so I stop by the next closest hardware store and get a dozen M8x1.whatever (don't remember fine or coarse from memory) steel ones, and tighten them up as best as possible out of fear without them the manifold could shake enough to break something more serious than a copper crush gasket. Anyway, by the time we got home (safe and sound, by the way), those nuts were all gone. Must have shaken loose. So now when I put anything on the car I think, how does one tighten this to ensure it is properly fastened!

Will try this "snug with new crush washer" technique and hope for the best. Just never know what with how much vibration goes on in these rambunctious little cars.
 
#21 ·
I'm an electrical engineer myself, I've learned to listen to the MechEs when concerned with bolt tightening. Only trouble is, I'm still having trouble believing them - let me deviate a bit to further express why I'm so concerned with torque specs! On a recent road trip (3000 miles round trip), halfway through the trip the exhaust manifold blows a gasket (cyl. 4). I check under the hood and find cylinders 3 and 4 manifold have NO NUTS on the studs! Not only that - the lower stud on cylinder 4 is GONE! I don't have any spare brass nuts so I stop by the next closest hardware store and get a dozen M8x1.whatever (don't remember fine or coarse from memory) steel ones, and tighten them up as best as possible out of fear without them the manifold could shake enough to break something more serious than a copper crush gasket. Anyway, by the time we got home (safe and sound, by the way), those nuts were all gone. Must have shaken loose. So now when I put anything on the car I think, how does one tighten this to ensure it is properly fastened!

Will try this "snug with new crush washer" technique and hope for the best. Just never know what with how much vibration goes on in these rambunctious little cars.
With respect to the exhaust manifold nuts, my experience is that they loosen regardless of how tight (or loose) they are. I treat them as a maintenance item and snug them up two or three times a year, typically at each oil change on the '88 Spider. Classic Alfa sells self-locking (not nyloc) nuts with a 12mm hex. I tried a set on the '78 car and they loosen too. Possibly, the cone washers that Paul Spruell sells are a solution but I am happy just checking them a few times a year.

I agree with the advice above to pay attention to torque specs but do the best you can on fasteners without a spec and/or access for a torque wrench. Using the right tool and a little common sense, particularly on fasteners 8mm or less in diameter, will produce satisfactory results. Experience will tell you when the manual lists a ridiculous specification.
 
#19 ·
I could not find it, had photos.. but a short answer on how to do it.. clip off old t stat from housing,, get dermal too, and shape the upper housing to fit a new of the shelf t stat, bring the old on into a parts store to find a close fit, then just dermal the housing to fit, you will be using the oem O ring for the seal, its not that hard, even I did it..
 
#20 ·
Bianchi2, was going to say, I cannot find a thread started by you on the topic. I can't picture what you have done for the modification either, or its purpose - the thermostat I installed fit fine with an eye-shaped rubber gasket I found on the car from a PO. I could not figure out what the purpose of the round ring gasket included with the thermostat could be used for.

Fortunately my mechanic says the car is running fine and the gauge or sender is the problem, more to come next week after I get the car back from him.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top