: N* running Hot, Real Hot



geoz3
06-12-09, 10:42 PM
I have bought a replica car with a N* motor. The motor is located in the rear of the car, and the coolent runs through through long tubes to rad, located in the front end. Not sure what year the motor is, or the milage. Car has a digital dash, the water temp runs up to 255, and the limp home mode kicks in. I'm running a 180 thermostat. Would the distance the water now runs, cause the car to oerheat? Would a lower thermostat help to keep the car cooler? The builder put in a custom built brass RAd, with one cooling fan that runs all the time, I just installed a second one, but no change. Any ideas?

Ranger
06-12-09, 11:16 PM
Check the purge line for flow. Check the surge tank cap to be sure it is holding pressure. Check the water pump belt tensioner. If all are OK, then get a block test kit from Napa and test the coolant for exhaust gases. When you figure it out and get it running right, put the correct thermostat in it.

Destroyer
06-13-09, 12:12 AM
Post a pic of the car. Sounds interesting. :cool2:

geoz3
06-13-09, 07:06 AM
Post a pic of the car. Sounds interesting. :cool2:


Here you are

geoz3
06-13-09, 07:17 AM
Ranger,

Before I took the car into paint, and it was overheating, I lost most of the coolant, I have not yet replaced it, so I'm running mostly water in the system. Will coolant help to bring the temp down? Also prior to paint, the car would boil over at 245, not it does not. It gets hot but, no boil over at 255. What is the correct Tstat for the car? I have read posts here that say 180 is correct?

Ranger
06-13-09, 10:33 AM
I think the OEM stat is 210. Maybe 200. Coolant won't bring the temps down. Actually water is a better coolant. The only reason for "coolant" is freeze and corrosion protection.

geoz3
06-13-09, 11:00 AM
Thnaks for the good info Ranger, I will check out all your suggestions today, hope it's one of the simple issues, not the head bolts.

jeffrsmith
06-13-09, 01:18 PM
You need to check and make sure you are getting coolant flow to the radiator and that the radiator fan is running correctly. Have you reached under the car to make sure that the coolant pipes on both side of the car are heating up? If they are not you may have a blocked radiator or an air-lock situation. Look under the car and make sure that the coolant pipes haven't been crushed by some half-wit at a garage (very common problem with Fiero's). After it overheated and boiled over the first time did you just add water without doing anything else? Typically these are very difficult cars to fill the coolant system and get all the air bubbles out, try backing it onto a set of ramps to get the rear in the air then take your time and add the coolant. If the fan is not coming on there may be an issue with wiring or a bad relay. Because your car is fiero based you may want to go over to Pennock's Fiero Forum and check out the technical section.

Good luck.

geoz3
06-13-09, 05:41 PM
Getting movement, both pipes are hot, tried all the burping tech stuff out there, I think that maybe the digital gauge may be the problem, is the sending unit near the intake manifold back near the T-stat? I might try a manual temp gauge and see what I get.

Ranger
06-13-09, 05:56 PM
I think the temperature sensor is on the rear of the right head (below the EGR valve).

Destroyer
06-13-09, 11:09 PM
Here you areThats pretty sweet. Bet it flys with a N*. Fiero based?

geoz3
06-14-09, 06:11 AM
Thats pretty sweet. Bet it flys with a N*. Fiero based?

Thanks, It's still a work in progress,I just put in 1.5 inch lowering springs in the front to drop the front end, need to get a full alignment, and put it on the highway. It's got the full Z06 braking system. Once I get the oerheating problem taken care of, it's going on ebay.

geoz3
06-15-09, 11:46 PM
Ran the car today and still overheats. At 255 water was comming out of the overflow tank, but it was not hot, it was cool. I opened the pressure valve on the front rad cap, and air came out, then more water from the overflow tank untill i closed the cap valve. The rad on the pass side is cool, a little warmer on the drivers side, but not real hot. When it cooled down, I opened the rear cap, and I had lost a lot of water. I filled from the rear and could hear a gurgel sound comming from the block as it filled. I started the motor with the rear cap off, at 160 hot water and air started comming out. I shut it down, added more water, capped it, and started it again. This time the temp ran to 195 and stoped there. After about 2 minutes I shut it down. I will rty a road test in the morning and see what happens. I have 2 fans mounted, 1 in front of the rad pushing, 1 in the rear pulling. Fans are hot wired to on when the key in turned, is this push pull helping or hirting air flow?

Ranger
06-16-09, 03:04 PM
Ran the car today and still overheats. At 255 water was comming out of the overflow tank, but it was not hot, it was cool.
Huh? 255 IS HOT!

I opened the pressure valve on the front rad cap, and air came out
I'd get a block test kit and test for exhaust gases in the coolant. Kind of sounds like you are pressurizing the cooling system with exhaust gases from a leaky head gasket.

geoz3
06-16-09, 10:27 PM
Ranger,

If this problem is so large, why has there not been a class action suit against GM to repair the motors?

Ranger
06-16-09, 10:31 PM
I don't think it is THAT large. Larger than it should be, but not THAT large. Other than that, I don't know.

geoz3
06-17-09, 01:22 PM
Huh? 255 IS HOT!

I'd get a block test kit and test for exhaust gases in the coolant. Kind of sounds like you are pressurizing the cooling system with exhaust gases from a leaky head gasket.


Ranger, is it possible that the builder crossed the hoses, with the car running I pulled the rad hose on the drivers side, no water comming through. The motor was reversed in my car, the fan belt is on the pass side, the thermostat on the drivers. Also under the throtle body there are 2 hose outlets, one has a hose hooked up, the other does not. Could
this be part of the problem?

Mark C
06-17-09, 06:15 PM
Serpentine belt on a N* is always on the passenger side, water pump is always on the drivers side near the transmission. The two small hose outlets under the throttle body are part of the purge line plumbing on N stars and its used to warm the throttle body. One line connects between the throttle body and a hose barb on the water pump housing, the other line goes to the top of the surge tank. this is how any air bubbles in the coolant get purged out of the system. If you don't have a purge line hooked up (doensn't really have to go thru the throttle body) the system will get air bound and not circulate any coolant in the system.

The hose connected to the water pump cover where the thermostat is located is the hot water out of the engine hose, the cool water return from the radiator connection is below that one.

geoz3
06-17-09, 10:15 PM
Serpentine belt on a N* is always on the passenger side, water pump is always on the drivers side near the transmission. The two small hose outlets under the throttle body are part of the purge line plumbing on N stars and its used to warm the throttle body. One line connects between the throttle body and a hose barb on the water pump housing, the other line goes to the top of the surge tank. this is how any air bubbles in the coolant get purged out of the system. If you don't have a purge line hooked up (doensn't really have to go thru the throttle body) the system will get air bound and not circulate any coolant in the system.

The hose connected to the water pump cover where the thermostat is located is the hot water out of the engine hose, the cool water return from the radiator connection is below that one.



The only hose going to the surge tank is from the rad overflow outlet just below the rad cap in the front of the car, which is where the surge tank is.

Where would the purge line oringinate from?

Mark C
06-17-09, 10:53 PM
There is a pipe nipple on the crossover manifold, just behind the water pump cover (if you were looking straight at the water pump from the dirvers side fender it would be at about the 4 oclock position). On an STS its actually holding the lower corner of the accelerator bracket onto the crossover manifold. The nipple is connected to a 3/8" tube that runs to the top of a stock cadillac surge tank. The nipple is how any air that gets to the water pump is vented off, without it the water pump will become air bound and not pump anything. Do a search on purge line, you will find all you ever wanted to know about it.

Ranger
06-17-09, 11:38 PM
If you pulled the radiator hose with the engine running and there is no flow, then there is a blockage somewhere. I assume it was at operating temperature? Sounds like they may have made a lot of modifications to this engine and that makes diagnostics hard. Also with the engine in the rear and the radiator up front there is a LOT of piping to get air out of.

geoz3
06-18-09, 06:57 AM
Thanks guys, I will trace down the hoses to see if I can find the purge line. Anyone have a diagrahm of the proper coolant flow? The guy that did the motor swap has fallen off the face of the earth. YA there is a lot of hose and pipe for the coolant to run through. I can't thank you guys enough for the help you have been to this point. I'll take some pics and post them of the setup I have, that might help also.

geoz3
06-18-09, 04:26 PM
Here are some pics of the setup I have. The first pic is of the one hose comming off the throtle body. The 3 others show the plumbing going to the theromstat water pump covering area.

Ranger
06-18-09, 04:53 PM
I see no pics. Is it just me?

STSS
06-18-09, 06:28 PM
No... No pics

geoz3
06-18-09, 06:42 PM
No... No pics


Sorry guys try these

Mark C
06-18-09, 06:56 PM
In your 3rd and 4th photo your purge line is the small line that comes out under the black bracket (thats a dogbone support bracket out of a seville or eldorado) and makes a U turn and goes back under your throttle body. Can't tell where the other end of it is from these pictures. there should be another metal tube on the left side of the throttle body (looking at it as these pictures were taken) that the other part of the purge line connects to. That line has to be connected to a surge tank, in order to vent any air that gets into the cooling system.

geoz3
06-18-09, 08:20 PM
In your 3rd and 4th photo your purge line is the small line that comes out under the black bracket (thats a dogbone support bracket out of a seville or eldorado) and makes a U turn and goes back under your throttle body. Can't tell where the other end of it is from these pictures. there should be another metal tube on the left side of the throttle body (looking at it as these pictures were taken) that the other part of the purge line connects to. That line has to be connected to a surge tank, in order to vent any air that gets into the cooling system.


Thanks Mark, I'll trace it down tomarrow and see where it goes. The guy that built the car, also built a custom copper rad he installed, it has a clamped line on the same side as the top rad hose, it may be the purge line. if it is, thats not doing any good at all is it, it seems it would just allow the air to stay in the system. It's about 8" below the rad cap. If it is the purge line, then coolant should flow out if I disconnect it, correct?

Ranger
06-18-09, 10:53 PM
Wait a minute. What the hell am I looking at? Why do I see what appears to be a radiator cap with an overflow hose under it seemingly in a radiator hose? :hmm: Like Mark said, this engine HAS to have a pressurized surge tank, NOT a recovery tank. The pressure cap and overflow are on the surge tank. I can't tell from those pics what you have.

geoz3
06-18-09, 11:16 PM
Wait a minute. What the hell am I looking at? Why do I see what appears to be a radiator cap with an overflow hose under it seemingly in a radiator hose? :hmm: Like Mark said, this engine HAS to have a pressurized surge tank, NOT a recovery tank. The pressure cap and overflow are on the surge tank. I can't tell from those pics what you have.

That does not sound good, LOL. The surge tank is in the front, by the rad. I think he put the rad cap in the rear to help with the burping. Should I remove it, and go with just hose in the rear? Could the current setup be the problem? Is it possible he hooked up the hoses to the rad in reverse? What would be the symtoms of the hoses to rad being reversed?

Ranger
06-19-09, 12:15 AM
Only he and God knows what he did, but he does not know what he's doing. YES, you have to get that cap out of the system. Replace it with a straight line. There should be no cap on the radiator either. The only cap should be on the surge tank and the purge line needs to run to the tank (just like a factory set up). That is most likely the cause of your problem.

geoz3
06-19-09, 10:15 AM
One more question, is water temp the only issue that will put the motor in limp mode? yesterday before the car reached hot temp, at about 190, in went into limp mode, stays in a low gear, and a red light the guy hooked up to the computer went on. I pulled over, turned off the motor, restart, it was fine for 45 seconds, then back into limp mode, temp about 210? I did this about 3 times, temp never did get above 220 on that run.

geoz3
06-19-09, 12:09 PM
OK, pulled the purge line at the dog one side, it's 1/8 with a nipple fitting, ran wire in and it's clear, however the opening from the nipple to the dog bone side of the tstat housing, is so narrow, that I can only get about 10 gauge wire through the opening to the tstat housing, is this correct or should I call roto router? started the car and noticed no coolant flow from the nipple. Also noticed the guy only has one wire hooked up to the temp sending unit. A blue wire from sending unit to the rear harness, comming off the right side of the sending unit, but no wire comming off the left termiinal. but i'm still getting a temp reading at the dash. Took the car out and temp only got to 220, however the red light came on, and it went into limp home mode at 220. The car sat for 2 years, is it possible that it just needs to be run daily to get everything working properly?

Submariner409
06-19-09, 12:28 PM
That orifice in the purge line nipple is not large - 10 ga. sounds about right.

The Northstar has such a different cooling system flow, what with internal and external bypasses and all - is it possible that there just isn't enough water pump "woof" to move coolant 8 feet forward and back ???

Have you considered installing a centrifugal electric "booster pump" in the hot line to the front radiator ??? It could be set to come on at some temperature, say 205, with a HD electric fan controller.

Ranger
06-19-09, 01:10 PM
Sounds like this guy has that cooling system all buggered up. The purge line is a 3/8" line. What you have there is WAY too small to do any good.

geoz3
06-19-09, 06:41 PM
I have not looked at a booster pump but I may.

jeffrsmith
06-19-09, 07:41 PM
You need to go over to the Fiero Forum and start asking questions over there. There are several people on that forum that have successfully put a N* in a Fiero and have had no problems - they are the ones who are going to be able to better answer the questions regarding the plumbing.

geoz3
06-20-09, 12:10 PM
Doing that also, this site has also been a big help.

**concours**
04-19-10, 07:10 AM
I don't think it is THAT large. Larger than it should be, but not THAT large. Other than that, I don't know.
Its large. Isee lots of cars in the salvage without a scratch, and i ask whats wrong with the car, and they say o it has a failed head gasket.

tateos
04-20-10, 12:27 AM
Its large. Isee lots of cars in the salvage without a scratch, and i ask whats wrong with the car, and they say o it has a failed head gasket.

I agree. What I don't agree with is notion that it totals the car. They frequently fail at around 100K miles - that makes a $4-5,000 car basically worthless. If the car is otherwise good, fix the HG and keep driving it for many more years. You've basically bought yourself a decent car you like for a couple thousand dollars - a lot less if you do the work yourself.