My real job is finally starting to slow down from it's seasonal insanity, so I was able to play with my toys for a little wile today. the Northstar in my IMSA has been running warmer than I felt it should ever since I put it in the car a couple years ago, but it wasn't so hot that I felt it was a real danger (225-230 on average), so I had let it go until today. today I ran it up on a friends lift and dropped the radiator tubes to check for dents/crushing, but found none at all. I've put in two thermostats since installing the engine, which made no difference, and I even bought one of Archies radiators last year, which also made virtually no difference over the stock rad. of course I've burped the system numerous time as well, even though I have what I feel is a very effective air purge/surge tank system made from part C-4 Vett and part Cad items. anyway... today I ran my infrared heat checker all over the entire cooling system and was surprised to find the return line from the rad, next to the thermostat housing, as well as the right side of the radiator, to be stone cold, even though the temp gauge was showing 225. all the heater lines and surge tank were hot as well. After a few other checks and a lot of head scratching, I determined that the thermostat had to be not opening. my theory is that the car has been using the surge tank, heater and associated lines for 90% of the engine cooling needs from day one, which obviously isn't enough capacity to do the job (but it did surprisingly well). for some reason the system finds it easier to circulate water through the heater system than the radiator lines, so there wasn't enough hot water getting back to the thermostat to open it fully, if at all. my solution.... I pulled the thermostat out and drilled four 3/16" holes in it to allow some water to circulate through the radiator loop at all times, and eventually heat the thermostat to opening temp. I drove the car 8-10 miles after the modification, and even though it was a bit slower than usual to come up to temp, when it reached 190 it settled in and never went higher for the remainder of the drive.
sometimes you just gotta do what works.

next project is to cut a hole in the decklid and make a "shaker" air box for the ITB setup.



Russ

Any pics of the process? I think I need to check mine too, its running about 190-210.

------------------




"Friends don't let friends drive stock"

Good detective work! Good fix!

So you know, my VIN 9 N* in my 95 STS usually runs 198 - 203 with the 190 thermostat. Cooling system is all new, I've had the car for 120,000 + miles, so your numbers seem good. (When they get up to 250 or 260 they start setting off alarms and shutting down.)

Okay, I guess within the ranges. Every since I switched over to the digital gauges I fond myself viewing the numbers more than with the stock gauges. I does something go up to 217 at a signal light.

I was cruising around today datalogging my northstar. Temp sat at about 203 degrees at cruise, but never got higher then 207 at an idle. It is a little higher then i'd like. I do have a crushed drivers side coolant line, but it doesn't seem to impeed the flow too much.

Phil

I've always put an 1/8 hole in my thermostats, it helps with trapped air.
Good job finding the problem.

Are you running the stock northstar thermostat, or something located elsewhere?

Here's a pic for ya' Madcurl:



it takes about 3-4 miles to get up to 190 now, where before it took only 1.5 or 2. problem was, it use to just keep creeping up after that. 190 is MUCH more comforting. I don't keep one eye on the guage all the time anymore
I wonder what just two 3/16 holes would do? I may try that some day.

Ryan. I'm using the stock thermostat system,

Russ

[This message has been edited by Russ544 (edited 07-19-2008).]

Thanks Russ for the good info. For now I will try it without any mods and then add the holes if it acts the same as yours. My guess is that it will act the same. There is so much heater line running to the front and then back I think it is acting as a radiator whether you are using the heater or not. Plus the fact that I added an additional 6 feet or so of aluminum heater line. Are you adding the "pellets" or whatever they are that help prevent corrosion?

Charlie

I haven't change out the original thermostat, but it only has about 30,000 miles on the engine so I think at this time its due. Was it hard to get too and how long did it take to remove the thermostat?

My gauge on on the center consol-blaring lights every time I look down, especially since the temp gauge is set to flash at 200.

[This message has been edited by madcurl (edited 07-19-2008).]

quote Originally posted by cptsnoopy: Are you adding the "pellets" or whatever they are that help prevent corrosion?

You'd better!

They help prevent headgasket problems. It's not a sure thing, but every little bit helps.

quote Originally posted by ryan.hess: You'd better! They help prevent headgasket problems. It's not a sure thing, but every little bit helps.

Thanks Ryan, I have not had to use them until now. I don't know if the system leaks yet or not so regular water will go in for a few hours to check it then I will replace with anti-freeze and pellets (or whatever they are called) to prevent problems... Is there a water drain near the bottom of the engine? It appears that I will need one if I have a system leak and do not want water sitting in the engine for weeks...

They're called "coolant supplement". Available from a dealer, or walmart if you buy "bars leak" powder in a tube. I'd check around the water crossover for leaks.

quote Originally posted by Russ544: My real job is finally starting to slow down from it's seasonal insanity, so I was able to play with my toys for a little wile today. the Northstar in my IMSA has been running warmer than I felt it should ever since I put it in the car a couple years ago, but it wasn't so hot that I felt it was a real danger (225-230 on average), so I had let it go until today. today I ran it up on a friends lift and dropped the radiator tubes to check for dents/crushing, but found none at all. I've put in two thermostats since installing the engine, which made no difference, and I even bought one of Archies radiators last year, which also made virtually no difference over the stock rad. of course I've burped the system numerous time as well, even though I have what I feel is a very effective air purge/surge tank system made from part C-4 Vett and part Cad items. anyway... today I ran my infrared heat checker all over the entire cooling system and was surprised to find the return line from the rad, next to the thermostat housing, as well as the right side of the radiator, to be stone cold, even though the temp gauge was showing 225. all the heater lines and surge tank were hot as well. After a few other checks and a lot of head scratching, I determined that the thermostat had to be not opening. my theory is that the car has been using the surge tank, heater and associated lines for 90% of the engine cooling needs from day one, which obviously isn't enough capacity to do the job (but it did surprisingly well). for some reason the system finds it easier to circulate water through the heater system than the radiator lines, so there wasn't enough hot water getting back to the thermostat to open it fully, if at all. my solution.... I pulled the thermostat out and drilled four 3/16" holes in it to allow some water to circulate through the radiator loop at all times, and eventually heat the thermostat to opening temp. I drove the car 8-10 miles after the modification, and even though it was a bit slower than usual to come up to temp, when it reached 190 it settled in and never went higher for the remainder of the drive. sometimes you just gotta do what works. Russ

A) How were you determining water temp? Scan tool? Would you mind going back over your CTS and gauge sender locations?
B) Northstars like to run warm
C) Northstars (and other modern engines) use recirculating thermostats.

This means that the thermostat is really two valves in one. When the engine is cold, the thermostat keeps the radiator circuit closed and the recirc open, so all the coolant gets recirculated back through the engine (instead of just having the flow blocked like a Chevy does). This helps ensure that the engine warms up uniformly. As the engine warms up, some of the coolant gets diverted to the radiator. In all cases, the amount recirculated is much greater than the amount that goes to the radiator.

IOW, the thermostat is always exposed to hot recirculating coolant.

You say the left side of the radiator was hot, but the right side wasn't? That sounds more like a radiator problem. You do have a purge cap at the radiator, right?

quote A) How were you determining water temp? Scan tool? Would you mind going back over your CTS and gauge sender locations?

wile driving or when diagnosing? wile driving I look at my Stewart Warner (not oem) temp gauge. When I was diagnosing, I used an infrared temp gun. all sensors are in the OEM location, with the exception of the temp gauge sender, which I placed in the (enlarged) old air purge fitting hole (on the water log outlet iow). the air purge was relocated about an inch away to the top of the water log (where the old lift bracket bolt once was).

quote B) Northstars like to run warm

to the best of my knowledge, the ONLY factory recommended thermostat available for the 98 cad motor is a 185* unit, which tells me that the factory designed the engine to run near that temp. Now if you mean that they will produce more HP at a warmer temp?.... yes they will. ideal temp for max HP, according to Alan at CHRF, is around 205*, but we're splitting hairs here, as the hp increase is minimal.

quote C) Northstars (and other modern engines) use recirculating thermostats. This means that the thermostat is really two valves in one. When the engine is cold, the thermostat keeps the radiator circuit closed and the recirc open, so all the coolant gets recirculated back through the engine (instead of just having the flow blocked like a Chevy does). This helps ensure that the engine warms up uniformly. As the engine warms up, some of the coolant gets diverted to the radiator. In all cases, the amount recirculated is much greater than the amount that goes to the radiator. IOW, the thermostat is always exposed to hot recirculating coolant.

Correct on all counts. in a perfect world .. however when you place a Northstar into a Fiero the perfect world goes into an elliptical orbit ! the distance the water pump has to pump water to and from the radiator increases by a factor of [lots]. the air purge and surge tank units are generally re-designed by one of us shade tree engineers, different radiators are being used, etc. etc etc.

quote You say the left side of the radiator was hot, but the right side wasn't? That sounds more like a radiator problem. You do have a purge cap at the radiator, right?

could have been a plugged radiator, except that the first one I used was a brand new Fiero unit I got in a parts car, and the one currently in use is a new 3 core Archie unit. iow... they're both good. the reason the right side of the rad was cold, and the left side (barely) warm was because there was no water circulation. I actually pulled off the hose at the water log return side wile running, and with the temp gauge showing 225* .... result.: no circulation in the rad loop.

I can't explain why the Northstar often runs hot in a Fiero, but I can tell you what I did to cure it. like I said at the end of my original post "sometimes you just have to do what works" . I suspect an air lock issue, but beyond that it really doesn't matter to me exactly where or what it was.... just that it's gone now

Russ

quote Originally posted by Russ544: I suspect an air lock issue, but beyond that it really doesn't matter to me exactly where or what it was.... just that it's gone now Russ

I think with that in mind I will drill a small hole at the top to let the air purge out and allow water to contact the thermostat. If that is not enough then I will make bigger holes like you did Russ.

Charlie

quote Originally posted by Russ544: to the best of my knowledge, the ONLY factory recommended thermostat available for the 98 cad motor is a 185* unit

195 F is factory. Now they make a 180F that they didn't back when I did my swap in 2003(?).

On a caddy the coolant fans don't turn on till 230F.

quote Originally posted by Russ544: could have been a plugged radiator, except that the first one I used was a brand new Fiero unit I got in a parts car, and the one currently in use is a new 3 core Archie unit. iow... they're both good. the reason the right side of the rad was cold, and the left side (barely) warm was because there was no water circulation. I actually pulled off the hose at the water log return side wile running, and with the temp gauge showing 225* .... result.: no circulation in the rad loop. I can't explain why the Northstar often runs hot in a Fiero, but I can tell you what I did to cure it. like I said at the end of my original post "sometimes you just have to do what works" . I suspect an air lock issue, but beyond that it really doesn't matter to me exactly where or what it was.... just that it's gone now Russ

Interesting. Burping my Northstar car did take some work. I think that when the system is filled with the lower hose connected to the thermostat housing, a bubble is trapped under the thermostat that doesn't escape until the thermostat starts to open. If the thermostat doesn't open, then the bubble stays. However, I can't think of why the thermostat wouldn't open... maybe I need to pull a water manifold apart and see exactly how it's set up inside.

Also, is your heater circuit plumbed like 87-88 Fiero or stock Caddy?

quote Originally posted by Will: Interesting. Burping my Northstar car did take some work. I think that when the system is filled with the lower hose connected to the thermostat housing, a bubble is trapped under the thermostat that doesn't escape until the thermostat starts to open. If the thermostat doesn't open, then the bubble stays. However, I can't think of why the thermostat wouldn't open... maybe I need to pull a water manifold apart and see exactly how it's set up inside. Also, is your heater circuit plumbed like 87-88 Fiero or stock Caddy?

Actually my heater system is set up more like the 84-86 Fiero.

Russ