Thermostat housing bolts seized

[cadh1]

I would appreciate some advice in changing my thermostat on a '94 Force 90hp. I've tried to loosen the four allen head bolts. They are extremely tight, to the point I think they may break. Is breakage a common occurance with these particular bolts, or is the metal of a high enough grade that they can withstand the torque? Would applying heat first be a good option? Since I am already worring, how much trouble am I in if they do break off? Thanks

 

[Firemedic09]

Re: Thermostat housing bolts seized

you might be able to heat them up a little, but not to much, dont want to damage or warp anything from the heat. if they do break off you can probably drill and tap the threads again. obviously you would want to avoid this but what can you do. have the bolts been painted over? might get something to clean them off if there is. hope this helps

 

[cadh1]

Re: Thermostat housing bolts seized

Thanks Firemedic09, I agree with your comments. It sounds like you've had experiance with seized bolts yourself. Yes there was some paint covering the heads and I've removed it. I'm seeing the heads move when I apply pressure. I'm hoping somebody online has struggled with these specific bolts, and has tested the limits of them.

 

[matt2002]

Re: Thermostat housing bolts seized

Soak the head of the bolt with a good penetrating oil like Sea Foam Deep Creep.Then tap on the bolt head with a punch.The idea is to set up vibrations drawing the oil into the threads.Once they start turning , turn them a little at a time and the back up , repeating until they turn freely.

 

[cadh1]

Re: Thermostat housing bolts seized

Thanks Matt2002, I've not heard of that particular brand of oil, but, it sounds as though you are giving it an indorsement. I will try that this evening after work, and let you know

 

[john from md]

Re: Thermostat housing bolts seized

Spray Deep Creep or Kroil penetrating oil on and around bolts. Heat with a hair dryer until you get it as warm as possible. Spray somemore oil. Wait overnight and then do the following.

Insert drift pin into allen head and rap several times with a hammer. This helps break the dissimilar metal corrosion up in the treads.

Next, use a 'T' type of allen wrench with an adjustable wrench or vise grips on the shank. Keep constant pressure on the 'T' while putting turning pressure on the adjustable or vise grips.

When replacing the bolts, use a good quality anti seize compound.

Regards,

John

 

[nabularach]

Re: Thermostat housing bolts seized

I had a the same problem a month ago and an impact driver and heat worked great. good luck

 

[matt2002]

Re: Thermostat housing bolts seized

If the bolts are that hard to get out replace them with new ones because the old ones will be fatigued.
As far as anti seize is concerned I usually use the gray Permatex brand but I've also heard it causes bolts to seize.I think the OEM recommended stuff to use is blue Loctite.

 

[Frank Acampora]

Re: Thermostat housing bolts seized

Two of those bolts--I forget, I think it's the bottom two--communicate directly into the water passage and corrode in quite nicely, thank you. It is very common to snap them off. Heat MAY help, but you will destroy the gasket and the rubber seal around the thermostat.

If you do snap bolts, you are not in much trouble but stainless is miserable to drill and remove, so you would be in for a frustrating job.

So, penetrating oil, maybe some heat, rock the bolts and take your time. If you have the luxury, remove the head and keep soaking the bolts for a couple of weeks. Otherwise, if you do not absolutely need to change the thermostat, leave it for the winter.

 

[cadh1]

Re: Thermostat housing bolts seized

Thanks everyone!!
I used all of the advice. The heat, oil, hammer/drift pin, vise grips, rocking the bolts etc. After a hard fought battle I got all four out, and I have the bloody knuckles to prove it. What a great feeling though! I will replace the bolts, and use the anti seize when I install the new thermostat tomorrow night. By the way the thermostat was badly corroded and frozen part way open, most likely causing my alarm issue. I pushed the issue tonight because I wanted to go fishing this weekend. Now I can. Thank you for taking the time to help a stranger.
Chuck

 

[matt2002]

Re: Thermostat housing bolts seized

What kind of antiseize do you plan on using ? I've seen reports of the gray permatex antiseize actually causing bolts to seize up.

 

[cadh1]

Re: Thermostat housing bolts seized

I checked with the local outboard repair shop when I picked up my thermostat, and they said they use the grey Permatex in their shop. So, I did use it on my project as well.

 

[john from md]

Re: Thermostat housing bolts seized

I just finished back flushing my engine and used grey permatex also. I have used this on water systems in cars, cycles and boats and find it works well and is easy to remove when you need to replace it. I also use it on my bolts that are prone to corrosion and it works well in that application also.

John

 

[cadh1]

Re: Thermostat housing bolts seized...THERE'S MORE

Re: Thermostat housing bolts seized...THERE'S MORE

...The reason for changing the thermostat to begin with was to address the overheat alarm being triggered. Upon using the motor with the new thermostat the same problem exists. At low speed the tell tale looks good, but, at WOT the tell tale stream actually gets smaller. So far I have checked the season old water pump impeller (still like new good vanes etc.), the housing was/is seated well, the metal cylinder/sleeve inside the pump housing has the top tab and does not spin, and the key is good. The water intake vents are clear in the lower unit. I pulled the new thermostat, and used a hose to flush the block. The upper hole of the thermostat opening flushed through the lower unit tube nicely (lower unit removed). The bottom section inside the thermostat opening backed up and only dribbled through the tell tale at full pressure. I'm not sure if this is correct or the overall problem. I tried the motor on the water again after flushing, and the alarm sounded. .....Once again, ANY help would be appreciated.

 

[john from md]

Re: Thermostat housing bolts seized

What a coincidence! I just started having the same problem with mine. I trouble shot it and found that the overheat sensor is grounding too early. It appears I have an earlier version and it goes off at about 160 degrees. The "newer" (my engine is an '85) sensors go off at 180 degrees. Unfortunately I can't find a replacement.

On my engine, it only happens at full throttle, 40mph. If I keep it at 35 MPH it will run fine all day long. Since I don't do 40 too often, I am not going to lose sleep over it although I would like to replace the sensor if possible.

Get one of the little infra red heat detector tools from harbor freight and aim it at the head when the buzzer goes off. It will give you the temperature and you can see if your sensor is working properly or not.

As for the tell tale not shooting as far at high speed, that may be because the thermostat is full open at that time and pressure takes the path of least resistance so the water is running down the leg and out the snout.

Keep us in the loop,

John

 

[cadh1]

Re: Thermostat housing bolts seized

Thanks John, by tell tale, I was referring to the two holes where the water shoots out on the back of the leg. Snout sounds like a good description. Sorry I wasn't clear. I did the touch test on the engine and it was too hot to keep my hand on for more than an instant, so I'm sure it is really overheating.... I can't help but think back to when the hose was pointed down the lower section of the thermostat opening, water should have shot out the snout rather than dribble have you ever tried that?....the sensor I have has a white lead. I think it is the one operating at a cooler temperature. So I'm sure you are correct about getting the hotter sensor for future. ....Also, I seem to have started two strings on this topic by mistake.

 

[john from md]

Re: Thermostat housing bolts seized

Did you remove the themostat or just replace it? At this point I guess you are down to pulling the lower and changing the impeller. Not a hard job but the lower gets heavier as we get older.

John

 

[cadh1]

Re: Thermostat housing bolts seized

"And the older I get, the better I was". ...I put a new thermostat in, and I had pulled the LU to look at the pump on Sunday. I have a new impeller, but didn't change it because the existing one is like new.

 

[john from md]

Re: Thermostat housing bolts seized

How about the level of your cavitation plate. Is it even with the bottom of the boat? You should have someone drive it while you are looking in the back at the cav plate. See if it just under water or if it is riding on top. If the water pickups are not getting enough water, that will also cause overheating. Sometimes this can be a trim issue in how you have the boat loaded and trimmed.

John

 

[JoeCrow]

Re: Thermostat housing bolts seized

WELCOME TO MY NIGHTMARE
Checkout
http://forums.iboats.com/showthread.php?t=262250
Had the same problem, did everything you did, problem went on for weeks, then months. I changed everything, thermostat, waterpump impeller, waterpump housing, even the prop, in an effort to lower the RPM's
There's a scan at the above link from one of my manuals discussing the bad sender
My resolution, BUY A NEW OPTIMA
Extreme I know, but my patience, much like my new bank balance,
is extremely limited
Try replacing the sender with one of the new "RED" ones
(if you can find one)
That may solve your problem without shelling out $8000
Good Luck