thermostat housing bolt size?

[Blknight692]

My '71 521 pick up was starting to run a bit hot so I got a new thermostat and was going to put it in when I snapped off both heads of the bolts on the housing. Gonna try to get them out with easy out and some heat, already got them soaking with some pb blast. But once I get them out, what size do I need to go get now? I did some searching and all I can find is 8MM I think. I pulled that up off of the olddatsuns.com web page.

Any help would be awesome.

Thanks

[Pacific coast Datsun]

I want to say they are 12mm bolts but not sure of the thread pitch. When you install the new bolts put some anti sieze on the threads & dont over tighten.

[Blknight692]

I used a 12mm socket to get them out, don't know if that helps anything or not. Both of them snapped real easy so they have probably been in there for a while, but go figure with the cathodic s of steel and aluminum, bad.

Thanks.

[metalmonkey47]

My '71 521 pick up was starting to run a bit hot so I got a new thermostat and was going to put it in when I snapped off both heads of the bolts on the housing. Gonna try to get them out with easy out and some heat, already got them soaking with some pb blast. But once I get them out, what size do I need to go get now? I did some searching and all I can find is 8MM I think. I pulled that up off of the olddatsuns.com web page.

Any help would be awesome.

Thanks

 

DON'T USE AN E-Z OUT if you can help yourself!! I had one snap off and almost trashed the head. If you do, make sure to use the biggest one you can fit in there.

 

 

 

http://community.ratsun.net/topic/23693-this-is-a-stupid-problem-to-be-having/

 

[Blknight692]

I'm going to take the housing off and see how much bolt I have sticking out and see what my options are before I easy out them.

[LenRobertson]

I checked an L-series thermostat housing. The bolts take a 12mm socket, and are 8mm X 1.25mm. But your 521 may be different. When you get the broken pieces out, you can take them to the store to be sure of matching the size. I hope you post how you get the broken bits out. I've seen posts before where people had the same problem, but never seen anyone post a foolproof method of removing steel bolt stuck in aluminum. Maybe PB Blaster will soak in over a period of days. If you can soak a bit of cloth with PB and cover that with plastic wrap, it might keep the PB from evaporating. Some people use left-hand drill bits to drill for EZ Outs, and say often the drill bit will back the broken piece out as you are drilling. But I think they are usually talking about removing from cast iron. The trick of welding a nut to the broken piece doesn't seem practical due to the tiny hole size in an 8mm nut. I also don't know if heating the aluminum housing with a propane torch helps at all. So maybe someone who has extracted broken 8mm bolts will chime in and tell us all the secret.

 

Len

[datzenmike]

I'm going to take the housing off and see how much bolt I have sticking out and see what my options are before I easy out them.

 

You risk snapping the bolts off going into the head. If the thermostat bolts broke, the mounting ones may too. Do this only if you must.

 

Is there any of the bolt showing above the aluminum?

 

 

 

 

I was very lucky there was enough to grip with vice grips. Use lots of heat around it, the aluminum swells slightly making the hole larger and the bolt easier to turn.

.

[LenRobertson]

datzenmike - Do you think soaking with Blaster or other penetrating oil does any good at all, or just go right to heat and hope? I've been lucky so far and haven't broken any bolts off, but I know my time is coming.

 

Len

[datzenmike]

datzenmike - Do you think soaking with Blaster or other penetrating oil does any good at all, or just go right to heat and hope? I've been lucky so far and haven't broken any bolts off, but I know my time is coming.

 

Len

 

I don't. Others do. Not saying they don't work just not for me.

 

I have never yet had a spray loosen a bolt that was truly stuck and adding more force will only snap it off. I have never had those sprays loosen it, ever. What I have found is if you have a rusty bolt and it's loose but tight to turn that stuff will make it a little easier to turn. I heat the nut or what ever the bolt is screwed into. I often reverse and go ahead slightly further then reverse then ahead going slightly further each time.

[metalmonkey47]

I also don't know if heating the aluminum housing with a propane torch helps at all. So maybe someone who has extracted broken 8mm bolts will chime in and tell us all the secret.

 

 

 

It does help, trust me.

 

The heat expands the aluminum around the steel, since aluminum is softer. The steel bolt is easier to remove when heated.

[wayno]

Did you break the thermostat cover bolts or the housing bolts that go into the head itself? The pic. in datsunmikes reply, is of the cover with broken bolts. If you cannot get them out then remove the housing itself and get another one from the "you pull it". Personally I would warm the engine up before I removed them bolts, meaning that you have given up on the housing and just want to get it off to replace it. wayno

[Blknight692]

Thank you all for your advise. Just a follow up. I was able to get 1 of the bolts out with a pair of vise grips and pb blast. Worked it forward and back a few times and out it came. The other on, the one closest to the head, was a complete fail. Grabbed it with the vise grips and tried to work it and it snapped almost flush with the housing. Hit it with more pb blast and let it soak for a couple of hours then tried the ez out. Complete fail again, snapped the ez out. Called up a couple of local shops to see if they had just the housing and got nothing. So as a last resort, I had to make the dreaded phone call to the ex wife, who's fiancé is in charge of a machine shop in town. He said he could work on it today but 1 of 2 things would happen. Either he is going to fix it or mess it up. I told him I'm junk yard hunting anyway, so if he could fix it, hes saving my bacon. So we will see where I'm at this afternoon.

Here are some pics of the housing.

 

[Blknight692]

Update, this weekend was an adventure to say the least. Got the part back from the ex and it looked real nice. Did a very good job getting the old bolt out. Props to them.

Had to make a new gasket for the housing to the head and for the thermostat. I could get a new one for the head but the part that all of the shops in town had must be wrong. The had some piece that has like 12 holes and slots with tabs that wouldn't fit anything close to what I had. I wasn't the only guy looking for one this weekend, somebody else was looking for gaskets for a '72 521 and running into the same issue. Good to know I'm not the only one in town. I figured out that the proper bolt length for this is a M8-1.25 x 27mm, problem is you can only get them in 25mm or 30mm. 25mm is to short to have a lock washer under and 30mm needs 2 lock washers, so I double nutted them and cut them down, perfect fit. I had to make a few gaskets because I kept getting a leak through the bolt hole on the bolt furthest away from the head. Took it apart and put it back together 3 times before I found the top thermostat housing had a pretty nasty pit next to the bolt hole. Called around to see if I could get the top housing and was told it would take 4 days to get one, at the earliest! Forget it, ordered it so I will have it later and then proceeded to jb weld my existing one. After I let it set, filed it down and then made sure it was flat and smooth, put it together and poof, it was done, no leaks. I have got to give props to my friend Jamie for putting up with me all weekend and helping me out, Jamies wife Sheila for letting him play all weekend and to my ex's fiancé Tim for getting me out of trouble with that bolt. Here is a pic of the housing after Tim got done with it. I will have another later today of it all back together.

 

 

[banzai510(hainz)]

yes the thermostat housing to head gaskets are hard to find.

What I do is find the gasket then get the sheet of gray gasket material and make spares.

Maybe the Felpro head gasket kits has them. I think they do.

 

Most thread pitch is 1.25 on nissans. at least on motor parts. 521s are funnk compared to 510 are soem stuff is not metric its SAE. Mostly brakes bleed and lugnuts. Maybe some otherstuff

 

 

I use allen head stainless bolts I got from hardware store ands use antiseize.

[Blknight692]

New update. Drove to work fine, temp hit 190 and stayed there. Later in the afternoon on the drive home I got about 5 miles from home from a 25 miles one way trip, and she started heating up. Got up to about 220 by the time I got home. Popped the hood and didn't see anything leaking. Waited for it to cool down then pulled the thermostat out, put it back together and took it for another drive to see if it changed or not. Temp started to climb, hit about 210 when I shut it off for the night. Called up Kragen and got a water pump on order, about $40 bucks without the clutch fan. Do I need a new clutch, didn't look like it had a clutch fan on. My fan is looking pretty nasty so should I get a new metal flex fan for it also? Any info would be great.

 

Here is a pic of the thermostat housing back together.

 

 

[banzai510(hainz)]

why you need a water pump? Unless the fan(inside vanes) all of a sudden just rotted out where there is non only thing goes bad on them is the bearing ,then it starts to leak and loose water.

 

your 521 have a clutch fan on there? Most 521 just have the 4 blade fan.Like the 510 type.

 

if you have a clutch fan type then you need to find the pully as the pully on the clutch fan type is with the water pump. 521/510 water pumps is just the pump. thats it.

 

I would try drilling a 1/8 in hole in the stat. for now as I see your 521 doesn not have the bypass from the lower stat housing to the water line. Some 510s/521 had these some did not. The 1/8 hole helps gradually warm up the rad and little bit of cavitation. Im sure when it was new it didnt matter but soemtime this helps.

 

tyr another rad cap also.if a spark plug looks nice white and clean then maybe its sucking up water or blowing hot gas into the coolant.

[Blknight692]

Thanks for the advice banzai. I'm just thinking next logical step with the water pump. Its only $29 and can't hurt to clean everything else out. I've replaced the radiator cap already and on the thermo I drilled out the little bypass pin and ran it, still acting the same. I do not have a clutch on my fan but I also do not have a shroud around it. My fan is pretty nasty looking with it being made out of plastic. Can/should I change it?

On a side note, I'm still having issues with my alternator bracket missing one of the bolts that go into the bottom of the block and so it allows the alternator belt to slip. I tightened the belt some more but now it doesn't charge as well. Did I make it to tight and would that have any effect on the water pump not working as well? Hmm, just might have to loosen it a bit and give that a try.

[banzai510(hainz)]

YOu know your truck I dont.

if the truck was running fine temp ature wise then I would say the radiator is OK.

if its acting up. then I look into the alternator mount. L16 use the smaller bolts and soemtimes they break in the block. I had some safety wired up so to dont loosen. But you nedd to get newer bolts.

also the bolts that go into the mount front frnt /back side break off alot.

 

the fan shroud I dont run on any of my cars. so on a6070deg days my car is fine. if your still overheats then yes you have a proplem. I dont dont the water pump will fix it or the fan unless the fan is on backwards if that is possible.

[Blknight692]

I think your right banzai on the water pump. I have it but didn't get to do anything yet. Just sitting around thinking and a thought hit me <crash, boom> well that was me falling out of my chair from the shock of me being so dumb. What if the lower hose has collapsed and failed. Every time I check it looks good but to hot for me to grab so I haven't. Went outside with Dr. Pepper in hand and grabbed it, yep, shes soft. Called up the parts store and will have one today, $13 for the lower and $16 for the upper. I'm gonna change them out and send some prayers to the Datsun gods...

[banzai510(hainz)]

Yes the lower hose can go soft. Back in the day those lower hoses used to have a coiled wire in them so it dont collaspe.

My yellow car would do this. I could actually see the hose collaspe when I reved up the motor once warm. Cant remember if it would collaspe when cold.

[Blknight692]

Update... Replaced the water pump, lower hose, upper hose, thermostat, upper thermostat housing with a cast iron one and the radiator cap. Filled it up with 50/50 and fired her up. Checked for leaks, good and clean. Took it for a 45 min. cruise and no issues. Woo hoo!

While I was deep in there and had everything removed I took a look at my alternator bracket to find out what I was dealing with. It turns out that I was just missing the rear bolt. Took the forward one out and went and bought 2 M10x1.50mm x 30mm long, washers and lock washers. Slapped them in and everything went together easy, true and straight! I'm a happy boy and most of my charging issues are gone as well! Yay me! Thank you for all you help!