I just received my mail order tuned PCM back from Chuck Cow day before yesterday. I also ordered a new 160-Deg thermostat from him which was included with my shipment. I installed the PCM Tuesday without any issues (car runs great), but I had to put off installing the thermostat until today (XMAS Eve).

So this afternoon I drained the radiator, removed the stock T-Stat and housing, no problem, then I tried to reinstall the new thermostat/housing, but IT WOULD NOT FIT into the opening. I knew the new T-Stat looked different in that it was a single integrated unit as as opposed to a 2-piece housing w/separate thermostat which I had stock. It also had a flange extension which my stock unit did not have (which I emailed Chuck about yesterday and he said just to ignore that). Both thermostats appear to have the same size mounting holes at the same distance apart - so except for the fact that the guts won't fit inside the water pump hole, it looks like the housing would work.

Well, needless to say, I was getting nowhere with the new T-Stat, so I called all the local auto parts stores at 5:00pm Christmas Eve - only one left open until 6:00pm (Action Auto). They said they had a 160-deg thermostat for a 2001 LS1 Coupe. So, I reinstalled my stock thermostat, refilled the radiator with DexCool mix and got there with 5 minutes left (had no choice since this is my only car). The part they pulled from inventory was the exact same unit Chuck sent me!!! Even the same manufacturer (MotoRad Germany) - so that did me no good. The parts guy pulled a stock 187-deg T-stat for a 2001 coupe and it was just like my stock unit???

So, now I am lost???

Here are the numbers that I measured with my micrometer:

Opening of bore hole in my water pump = 1.875"
Max Width of shoulders on stock T-Stat = 1.662"
Max Width of shoulders on my new 160-deg T-Stat = 2.032" ???

So what is going on here?

The only thing I can think of that might be different in my case is that the dealership replaced my engine under warranty a year ago with another "newer" LS1 which already had a new water pump attached from the factory. But I am not aware that they changed the diameter of the T-Stat opening in the water pumps over time.

I tried calling Corvettes of Westchester this afternoon, but I am assuming everyone was gone for XMAS break.

Any ideas on what my problem is and how to solve it?

 

Call me now.... I'm here.

When your short block was replaced, they automatically gave you the 04 and newer pump... No big deal...I'll exchange it for you right away.

Nobody services the 97-03 water pump...The only one available is the 04 and newer.


Chuck CoW

 

Man, what took so long??? I did not let go of my mouse button before you responded to the post???

------ (RESPONSE from Chuck via our ensuing phone conversation) ------

Apparently, since GM replaced my engine with a new one last year under GMPP - it appears I got a new 2004 designed water pump unit already attached to the engine. Chuck assumed that the dealership reused my previous original 2001 Water Pump. So, he said he will send me out the correct T-Stat on Saturday.

Problem solved.

THANKS FOR THE QUICK RESPONSE CHUCK!!!

 

Talk about QUICK service, and on Christmas Eve!!!!!!!!!!!!!!!

 

REALLY! It is comforting to know that there is someone else out there with no life! For me Christmas is just another WORK day.

 

Chuck will take GOOD care of you! He has some of the BEST customer service available!

Bill C

 

Great customer service!

 

OK... I got the replacement thermostat. This time there was no problem with the shoulder width - it fit inside the water pump bore fine. The replacement unit was more like the stock thermostat in that I had to reuse the stock housing. The new one came with an integrated gasket just like the stock one I removed.

My only concern was that I noticed that the new T-stat had about a 1/16" gap left between the housing and the water pump after hand tightening the two bolts (i.e. I had to use the ratchet and socket to get the housing to mate with the water pump flange since apparently the spring on the T-Stat had to be slightly compressed to fit up). Is this small amount of "PRELOAD" normal?

I torqued the two bolts to 11-ftlbs, but today I noticed that I have developed a very small leak coming from the housing where it mates up. I just wondered what might cause that and if this new thermostat (with the small amount of preload) is not the reason.

Other than the leak, the new T-stat seems to be working fine and holding the operating temp at 160-degrees.

 

Does the housing of the thermostat contact the water pump housing, i.e., is there a gap?

O-rings generally will not leak unless they are damaged or the compression is incorrect. If there is a gap the compression of the o-ring may not be correct. The other thing to check is the hose. Sometimes the hose connection will leak and it will run to a location that indicates the housing is leaking.

 

There was no gap once I tightened the bolts and there is nothing leaking from the hose connection. Guess I will just need to buy a new gasket and try again? I really took my time, so not sure what is wrong, but obviously the gasket is leaking?

 

Looks like Chuck guessed what my problem was. Apparently there is a notch in the housing that I did not notice that lines up with a tab on the rubber gasket. Mine was not lined up last time and that was causing the slow leak. I almost did it wrong again! ... just did not notice that the gasket had to be aligned?

 

I thought this was an o-ring. Gasket notch? Got any photo's? This is likely something all of us will face in the future since the LS1 pump is no longer available.

 

Hopefully the attached pics will explain.

The 160-deg T-Stat I initially received from COW for my 2001 LSI was a single piece integrated Tstat/Housing with a regular O-Ring. As I understand this would work for an original 2001 LSI. In my case, the dealership replaced my engine last year under warranty with a newer unit (I am assuming a 2004 model?). Therefore, my newer designed water pump was different. The initial T-Stat COW sent would not even fit inside the water pump bore. Therefore COW sent me a replacement separate T-Stat and gasket that required that I reuse my newer stock housing. Unfortunately I did not notice the notch in the housing and the previous unit did not have an O-ring orientation, so when I reassembled the 2nd time the gasket tab was trapped between the flanges causing a tiny slow leak (but not mechanically visible when torqued). 3rd time was a charm - no leaks now!

 

Good pics and description.

 

Excellent, thanks for posting.

 

I am replacing my water pumP and thermostat housing in MY C5 2002 .

I have a new AC Delco water pump (252-846) and 2 piece thermostat and housing housing (15-11057) . While the housing fits ok, and I do have the notch in the oring
gasket lined up correctly, The thermostat spring has to be compressed slightly (~1/4") when the bolts are installed. is this normal?
I saw this same question asked in this thread, but I didn't see where the compressed spring question was answered. my gasket if fine I can hand tighten this flush by placing my thumb on the housing to compress the spring.



"apparently the spring on the T-Stat had to be slightly compressed to fit up). Is this small amount of "PRELOAD" normal?"

 

Yes, it must be compressed a bit.... the MOST IMPORTANT aspect of the stat swap is that the Largest outer diameter o-ring

is correct and snugly (never loosely) fits the bore in the housing.

Also, it's very important that the stat is "clocked" in the housing by way of the little tiny square nipple

on the outer diameter of the o-ring. Very important. It goes in the square notch on the housing.

Some good advice is it REMOVE the large hose from the housing before trying to re-install it.

It's pretty awkward to lean over the fender and wrestle the assembly into place to align the bolts with the big hose

still attached.

Chuck CoW

 

Hi Chuck CoW, Mike Venth here in Va. (Bill C's) friend. Hay Bill...
Just wanted to say thanks again. Glade I sent the Stat in with the ECM/PCM for the tune,made it easy to get the right one first time.
My 01 is rocking and rolling with your tune and up grades. Thanks for the Veteran's discount also.
Hope you and the folks in the shop have a Merry Christmas and Happy New Years..
Mike Venth

 

Thank you very much for your Business AND your SERVICE!

Enjoy your tune my friend!
Chuck CoW

 

I actually installed the T-stst to the water pump in the house before the pump was installed to the car, but if not having the hose disconnected is a great idea.

The rubber gasket had a notch, and I made sure it was on the slot correctly,. It also included a paper gasket that went around, but did not touch the rubber gasket. Looks like it Acts as a buffer to prevent over squeezing the gasket. The directions said to only use the paper gasket if using the rubber gasket not using the o-ring. Seems to have sealed well. The water pump came with the paper gasket and a new o-ring. Said to use o-ring with 0one piece design and Pape gasket with 2 piece rubber seal design

Upon playing with the old t-stat, I understand now that there is 2 springs on it. The one that compresses a little appears to be a check valve to the water flow from the engine. The normal t-stat spring doesn't compress when installed.

Thank You again for the advice it all back together and running fine now.