Changing the thermostat questions

[Michael]

I have finally gotten around to working on my overheating truck and thought a good place to start would be to change the thermostat. At first I didn't think it had the rubber seal that you are suppose to remove and replace, but now I am not so sure. The TM pic looks like a split ring, but the picture from the other post looks like what I have which looks to me like a brass ring with rubber underneath it? Kind of like an axle seal. I decided to test my old thermostat against the new one form NAPA. The old one doesn't seem to open up as wide and closes quicker than the new one. But is there enough difference to make a truck over heat? I think I am going to replace the hoses and I may just go ahead and get the radiator rodded since it is half way off anyway. Is is OK to just get NAPA to cut some hose to length or should I order new ones from a vendor? Any recommendations?

Link to the overheating thread:

http://www.steelsoldiers.com/index.php?name=PNphpBB2&file=viewtopic&t=23450&highlight=

 

[Michael]

From the TM. Number 9 is the part in question.

 

[Stan]

I've used whatever hose was the most convienant to get. NAPA and local parts stores with no problem. Flush the block while you have it apart.

 

[WillWagner]

That is the correct seal in the housing, it is just a newer type.

 

[Michael]

Are the newer type seals meant to be reused and if not is there a source for them?

 

[WillWagner]

Well, they can be, but since it's apart, i'd get anothe one. Did you try Saturn or Memphis?

 

[Michael]

I haven't tried to get the seal out yet. It seems to be in there pretty good and I didn't want to damage it before I sourced a replacement. The lack of posts makes me wonder if anyone is bothering to replace it. Here is the part number from the AUGUST 2006 TM:

NSN 5330-00-848-9943 part number 7748859 SEAL,PLAIN ENCASED

Saturn Surplus lists it on their web site but doesn't have a price by it so they may be out of stock.

I tried all the part numbers on this page at NAPA online and didn't get a match:

http://www.wbparts.com/rfq/5330-00-848-9943.html

 

[Michael]

I printed the page from the link in my last post and my local NAPA dealer was able to cross two of the numbers to a NAPA number. It is 4662. It is even made in the USA. One of the numbers was the one from the TM: 7748859. I haven't tried to put it in yet, but thought I better post the number while I had it close to the computer. It only cost $3.11.

 

[Michael]

I regret to inform the list that the above seal doesn't work. It is the correct outside diameter but the inside diameter is too small. The thermostat is suppose to fit inside it and it does not. I ended up putting the truck back together without a seal since I had flushed the block with tap water and it was suppose to get down in the lower twenties last night.

 

[TenTires]

Look guys, a newbie found a thread that had already been posted and added to it instead of making a new one.......

Anyways, what did you ever find out about this o-ring? I pulled my stat tonight and cooked it and It looks like its opening fine to me (190 or so) and it looks like its open as far as yours. Thing is, after pulling the stat out of the housing, I looked at my o-ring and the metal part is fine but the rubber on the back side is coming off. Does this matter/ should I just pull the rubber off, toss it and keep on moving? Also, do I have to replace the gasket on the housing or can I just scrape the old one off and seal it up with RTV? Thanks!!!

 

[WillWagner]

It is a teflon seal. Get a new seal. The coolant will bypass the stat and lead to an overheat on a long pull and run cold around town. The new sael will be very tight. After the seal is installed in the housing, it will take a bit of force to install the stat. Try pushing the seal on the stat, pulling it off then installing the seal into the housing. It makes the stat easier to install.

 

[TenTires]

Roger that. Change the seal it is. Was there ever a correct part # found for this seal?

 

[Michael]

What I bought may have been old and stiff. It sure looked like the right part. I tore it up removing it and haven't tried to do any thing about since I put it together without a seal. It doesn't want to warm up as it is but that is better than overheating.

 

[Michael]

It is a teflon seal. Get a new seal. The coolant will bypass the stat and lead to an overheat on a long pull and run cold around town. The new sael will be very tight. After the seal is installed in the housing, it will take a bit of force to install the stat. Try pushing the seal on the stat, pulling it off then installing the seal into the housing. It makes the stat easier to install.

This sounds like the voice of experience. Where did you get your seal?

 

[TenTires]

Hey Michael, not sure if you resolved your issue with this seal or not but I was able to locate one through Saturn Surplus. Ill put all the info @ the bottom of this post. I e-mailed them about it and they said they had it in stock so I ordered it. $6.50 shipped and they got it to me within 48 hours of ordering it! It wasnt hard to get out or in. I pried the old one out with a screwdriver and formed up some wood blocks to beat the new one it. Put it in yesterday with my new radiator and she runs like a top!!

Heres the info:

3599 M35 M35 Seal, Engine 7748859 5330-00-848-9943 S2-B

 

[Michael]

How much force did you have to use to get the thermostat seated into the seal? The one I got from NAPA was so tight it would have took a hammer to get the thermostat in place. I just couldn't see the thermostat opening and closing as tight as it was.

It may just be the difference in the way the pictures were taken but your original picture looks like the NAPA seal and your new one looks like the metal flange is a little bit smaller resulting in a slightly bigger inside diameter.

 

[randyscycle]

I picked up a new thermostat and seal from NAPA the other day and have them laying here right now on my desk.

The thermostat is part number 358-180 and the seal part number 4622. THe seal does fit the thermostat and can be pushed on by hand. I just did it. It is snug, but can be done without any serious force. Seems that it would work just fine. I will install it next weekend, so if any problems, I'll be glad to post up.

 

[randyscycle]

Update:

I replaced my thermostat in the deuce this afternoon. I used the NAPA seal and thermostat and had no problems at all with fitment. I did notice that the seal was a little tighter after driving it into the thermostat housing, but I was still able to push the thermostat in by hand.

I'd also pass along this recommendation: I was doing them anyway, but if you hadn't planned on it, replace all of the hoses! Mine looked OK from the outside, but inside they were beginning to rot and crack. Particularly the ones from the cylinder head to the intake manifold. With the new working thermostat, it would have been a matter of time before a hose somewhere would have failed. I also added a coolant filter at the same time. There was a fair amount of loose sediment and rust in the cooling system, even though the coolant looked fairly clean.

 

[Michael]

I bought another seal from NAPA and test fit it on my old thermostat. It went on OK at room temp. It is a good idea to push it on before you put it in the truck. The first time I did it I didn't and it was about 20 degrees and getting dark and it didn't want to fit so I just ripped it out.

 

[roger-wilco-66]

Just a side note:
I wanted to put a "thanks for the useful information" tag on a post in this thread but couldn't decide upon which one it should go. So here's a collective "thanks" to all of you for documenting this issue so well!