: where is thermostat

01-23-13, 11:15 PM
My 02 deville keeps overheating and blowing weak heat can anybody help

01-24-13, 04:28 PM
Can't find tstat on 02 deville please help

01-24-13, 06:32 PM
It's in the thermostat housing at the water pump drive on the driver's end (the rear end) of the engine.

Click my username, open the profile. Left column - 2 albums, 6 pages of stuff for your engine - MANY of the water pump and cooling system.

If you didn't know where it was, why do you need to do something ??? You may be getting over your head: This is like no cooling system you may have worked with before.

01-24-13, 06:34 PM
Wrong forum - none of these engines are yours - you have a VIN Y 4.6 Northstar DOHC engine.

Moved from 4.1, 4.9, etc.

See my previous post - you need to do a bit of homework before you start messing with thermostats. (and they're very reliable in this group of engines.................. Northstar.)

What's "overheating", and define "weak heat".

01-24-13, 08:49 PM

Thermostats are pretty damned reliable. Can you give us more specific symptoms?

01-25-13, 12:26 PM
It's overheating and not blowing heat full of coolant had,head gaskets fixed now overheating and blowing cold air

01-25-13, 01:31 PM
What was the head gasket repair method? Studs? Timserts? Helicoils? NormSerts? Arp studs?

Has a blocktest been done. Help us help you man

01-25-13, 01:45 PM
I bought the head gasket kit for 250 so everything got changed water pump not leaking water check for clogs and didn't see none so I'm thinking its tstat just from temp going up and no heat

01-25-13, 02:52 PM
What "head gasket kit" you do realize the block itself needs to be re-tapped and fitted for more courser threads via stutds or large serts?

01-25-13, 04:24 PM
My 02 deville keeps overheating and blowing weak heat can anybody help

You have 1 of 2 problems eather it's low on coolant or its the head gaskets going bad I've seen this 100 time or more time in my shop I had for over 37 years and its not just caddies its anything with coolant and head gaskets in it . There not completely blown yet but the end is coming soon what happens is its blowing compression into the cooling system and it is aerating the system . A good way to test it is when it's cold put a pressure gauge on the radiator ,
.where the cap goes start it up if it starts building pressure in a couple of minutes that a good sign . If you don't have a gauge you can feel the upper hose if it gets hard before it gets warm that's also a sign ... Does it have hi mileage? Any more question please feel free to ask .

01-25-13, 05:09 PM
the purge line could be clogged ... that will present a situation where there is no coolant loss and correct coolant level but you get overheating

01-25-13, 11:59 PM

Check that purge line first. If that's OK, do a block test.

01-26-13, 12:11 AM
Changed thermostat not hard to do at all some guy on here acted like it was changing motor Lmao purge line ???? Where is that???

01-26-13, 12:28 AM
The purge line is the 3/8" line that runs from the W/P housing aka crossover manifold to the surge tank.

This is Sub's Seville. Yours should be on the passengers side, but will look the same.


01-26-13, 12:39 AM
Thanks for pic wat about bleed the line for air

01-26-13, 10:05 AM
The purge line IS the air bleed line. It "purges" air from the cooling system.

01-26-13, 10:20 AM
ecoleman, In your Deville the coolant reservoir is over on the passenger side. The purge line runs around past the P/S pump, under the engine cover, and over to the hollow bolt/nipple at the water crossover - right next to the water pump cover where you changed the thermostat.

That line should flow a constant small stream of coolant into the reservoir. It is at the high point of the cooling system and so bleeds off air from the main system to prevent water pump cavitation and loss of coolant flow.

To test the purge system with the engine cold, remove the small hose from the side of the reservoir, remove the pressure cap and have an assistant start the engine normally while you hold the hose in the open reservoir neck - you should have a steady coolant flow. If not, you need to remove the entire hose/piping and clean it out, and use a suitable sized drill bit, hand turned, to clean out the metal nipple/bolt on the engine. IF the purge lne cannot be unclogged it can be replaced with a length of proper sized fuel hose - that has a braid jacket and will withstand the 16 psi cooling system pressure: The entire system is under pressure when the cap is installed.

Proper cold coolant level is about halfway up in the reservoir - follow that arrow across the top and down the sie of the reservoir.

01-26-13, 10:26 AM
THAT'S the picture I was looking for! :bang2:

01-26-13, 10:29 AM
Copy it.........

01-27-13, 10:15 AM
Thanks guy pulled purge line thick crap all through it replaced line drove all day no problems

01-27-13, 10:21 AM
You also need to clean out the hollow bolt that the purge line attaches to at the other end. If the line was clogged with that sealant tab residue, then the hollow bolt surely is and you will still be overheating.

DO NOT use those damned sealant tabs anymore. :tisk: