looking at new to me 1990 Coupe Deville, couple of questions [pics!]

[lothos]

It will take a few drive cycles to get the coolant level stabilized in the system. It is just the air working out of the system.

I don't think the gurgling is abything to worry about - it is probably the coolant working its way into the overflow/recovery tank after the engine is turned of.

As far as the heater core goes, you said both heater hoses are cold??? The inlet hose to the heater core (usually off the intake manifold but check the shop manual to be sure) should be warm. The outlet hose should be approximately the same temperature. If the outlet hose is cooler than the inlet, there is a restriction in the heater core. If you find that is the case, I would backflush the heater core with hot water pressurized if possible and then forward flush it. Then reconnect the hoses and fill the system.

I can specifically hear the coolant inside the firewall, not up by the recovery tank. Does that make a difference?

BTW does the cap on the overflow/recovery need to seal tight? Mine does not.

I don't think I explained the hoses very well.

There is the big radiator hose that goes from the radiator to the thermostat, it is hot.

Then there is the hose coming from the intake manifold and it is hot.

There's a T next to the firewall where the hoses split off, and they are warm.

There appears to be 2 coolant hoses (one might be a vacuum line?) coming from the firewall and going to the engine. They were cold. I can re-check this tonight.

[adallak]

The noises you hear are probably coming from the heater core. As KHE said, 4.* cooling system is very simple. The air will eventually get out into the reservoir after a few heating-cooling cycles. The cap of the reservoir is NOT airtight. Just add some coolant to the reservoir in a week or so and forget it. The plastic T is so called heater valve. The hoses attached to it are heater hoses.

[lothos]

The noises you hear are probably coming from the heater core. As KHE said, 4.* cooling system is very simple. The air will eventually get out into the reservoir after a few heating-cooling cycles. The cap of the reservoir is NOT airtight. Just add some coolant to the reservoir in a week or so and forget it. The plastic T is so called heater valve. The hoses attached to it are heater hoses.

Thanks for the replies guys

Good to know that the overflow reservoir cap doesn't need to be airtight. I think it does on the northstar?

Could the empty overflow tank have allowed air into the system? It was empty, I filled it and will keep it filled now.

Could the plastic ends on the heater core be cracking and allowing air in?

I noticed it last night because I sat in the car after turning it off, which I normally don't do, so I'm not sure when this started.

KHE: I checked the heater lines again. The heater valve T goes to the heater core. That line was warm. The return line today was also warm, I'm pretty sure it was cold last night. I think maybe the inlet was warmer than the outlet hose.

To flush the heater core... is this correct? Pull off the inlet and outlet lines, first flush the inlet then the outlet?

The heat seemed to be a little warmer today than last night, but last night it was 20F outside and today was 40F.

I guess I'll keep my eye on it?

[the gold2]

Sounds like you're on your way.

How about if you keep the heat on full for several days and see if it circulates on its own to normalize? Probably has an air bubble moving. It will burp on its own via reservoir tank with time.

My 4.9 liter Eldo always has the temp at 65F as a default.

[lothos]

regarding the heater core: I've still been hearing the gurgling noise. It seems to have gotten quieter, though. Went for a drive and it seemed to still blow lukewarm. The heat seemed to get hotter when I accelerated, is that weird?? Parked it and shut it off, and could hear the light gurgling noise. The outlet hose wasn't very warm. Started the car back up and let it idle for a while while I checked under the hood. Tried the heater again. Put it down to 60 and it blew cold, and out of the upper dash vents. Turned it up progressively to 90 and it got warmer and blew out the floor vents. It seemed to blow warm now and not lukewarm. It seems like the outlet hose is also getting warmer at this point but not as warm as the inlet host.

I think you guys are on the right track here. The gurgling before was louder and lasted longer, and now it's much quieter and doesn't last as long. The heat also seems to be getting better now, and I'll see how it is tomorrow.

I take it my empty overflow tank let some air in the system?

Sounds like you're on your way.

How about if you keep the heat on full for several days and see if it circulates on its own to normalize? Probably has an air bubble moving. It will burp on its own via reservoir tank with time.

My 4.9 liter Eldo always has the temp at 65F as a default.

I actually DID have it up to 90 for the last drive I just did. I'll continue to do that and see if it helps. Thanks for the suggestion!

[KHE]

The Northstar cooling system is different in that the surge tank is pressurized - the radiator cap is on the surge tank. The 4.1, 4.5, 4.9 engines have a conventional overflow tank that is not pressurized. The radiator cap is on the radiator itself with an overflow tube to the tank.

To flush the heater core, drain the coolant and blast hot water through the inlet first and then through the outlet. It helps to have hoses connected to the heater core so that you can capture the flush water. I have a setup with an air compressor fitting and a valve so I can pressurize the flush water up to 120 psi and use hot water to flush heater cores. Radiator shops use 180 psi but my compressor only goes up to 120 psi - it seems to work fine. The air pressure is turned up gradually.

There is coolant flowing through the core constantly, regardless of the set temperature on the climate control panel. The temperature is controlled by the blend door.

Have you set the temp to 90 degrees after the engine is at operating temperature and felt the outlet ait to see if it was hot?

If the heater core tank(s) were cracked, the carpet would be soaked with antifreeze and you would smell it.

[adallak]

Sounds like you're on your way.

How about if you keep the heat on full for several days and see if it circulates on its own to normalize? Probably has an air bubble moving. It will burp on its own via reservoir tank with time.

My 4.9 liter Eldo always has the temp at 65F as a default.

Turning heat on full will only open the airmix door to let more airflow through the heater core to the cabin. It will NOT affect the coolant flow through the heater core.

When it is not very cold outside, I adjust the heat to 90 but do not turn the blower on. That opens the air mix door maximally and let some warm air in. Often, it is enough to have comfortable temperature without the noise of the blower.

When you accelerate, RPM increases so increases the flow of hot coolant through the heater core which results in increased heat. Besides, an engine under load generates more heat than an idling engine.

[the gold2]

THX KHE and Adallak for the insight on the mechanics of the heater.

[lothos]

Well, I replaced both front rotors and calipers last night. I also noticed my driver's side outer tie rod end was throwing grease and could move by hand. Part was only a month old, but it had a free replacement and I replaced it last night.

The car still "shifts" when I apply the brakes.

Driving down the road: the car pulls to the right. To drive straight the steering wheel is tilted to the left.

Brakes applied: front end seems to shift to the left. Steering wheel is now aimed correctly.

Can a bad alignment cause this? What else can cause this?

Still waiting for my buddy to get time to do my inner tie rods before I can get an alignment done.

[the gold2]

Can a bad alignment cause this? What else can cause this?

My quick response is yes, in general to some degree, it can be a factor.

[lothos]

My quick response is yes, in general to some degree, it can be a factor.

You were right. Got the inner tie rods done tonight with my buddy's help and there's no more shifting/swaying when I apply the brakes Hopefully I can get in for an alignment tomorrow.

Seems the grease being thrown around is from the CV axle. Buddy said to just leave it be until it starts clicking/making noise and then replace both sides, so that's what I'll do.

Oh. My heater core is still making a gurgling noise when I turn the car off. Don't seem to be losing any coolant, and the heat seems to be a lot warmer now. How long can it take for the air to work it's way out?

[KHE]

My quick response is yes, in general to some degree, it can be a factor.

You were right. Got the inner tie rods done tonight with my buddy's help and there's no more shifting/swaying when I apply the brakes Hopefully I can get in for an alignment tomorrow.

Seems the grease being thrown around is from the CV axle. Buddy said to just leave it be until it starts clicking/making noise and then replace both sides, so that's what I'll do.

Oh. My heater core is still making a gurgling noise when I turn the car off. Don't seem to be losing any coolant, and the heat seems to be a lot warmer now. How long can it take for the air to work it's way out?

Replacement aftermarket axles are JUNK. The boots are so soft, they self destruct within a year or two and even with lifetime warranty axle half shafts, you will be replacing them for the rest of your lifetime...

Aftermarket axles seem to be larger and can have balancing issues also. My suggestion would to buy new OEM boots and clamps and repair the existing axle before it starts to click and make noise. Once they click and make noise, the CV joint is destroyed.

[lothos]

Replacement aftermarket axles are JUNK. The boots are so soft, they self destruct within a year or two and even with lifetime warranty axle half shafts, you will be replacing them for the rest of your lifetime...

Aftermarket axles seem to be larger and can have balancing issues also. My suggestion would to buy new OEM boots and clamps and repair the existing axle before it starts to click and make noise. Once they click and make noise, the CV joint is destroyed.

Wow, I didn't know that, thanks for the tip.

Looking at RockAuto it seems there aren't any OEM axles OR boots available. Would that boot and clamp be a dealer part?

Or would it be possible to locate the rip on the current boot and fix it with something like JBWeld?

[the gold2]

Boot patch-repair is futile. You might patch it for a bit but it will bust up.(my former Dodge had that problem)

Replacing the entire boot before it goes bad is the best like KHE says.

I've even seen, moons ago, boots that fit over the old but that is goofy.

sorry I don't know a vendor.

maybe if you phone Rock Auto they may get it for you even if it is not listed online. Likewise other vendors.

Glad your car is shaping up. Its a nice classic model.

[KHE]

Replacement aftermarket axles are JUNK. The boots are so soft, they self destruct within a year or two and even with lifetime warranty axle half shafts, you will be replacing them for the rest of your lifetime...

Aftermarket axles seem to be larger and can have balancing issues also. My suggestion would to buy new OEM boots and clamps and repair the existing axle before it starts to click and make noise. Once they click and make noise, the CV joint is destroyed.

Wow, I didn't know that, thanks for the tip.

Looking at RockAuto it seems there aren't any OEM axles OR boots available. Would that boot and clamp be a dealer part?

Or would it be possible to locate the rip on the current boot and fix it with something like JBWeld?

The OEM boot may be a dealer only item. You might be able to find a boot at a parts store but I would only use that if it were the hard, thermoplastic type which is what the OEM boots are. If the boots are made of soft rubber, they won't last.

There is no way to repair the existing boot - they usually crack in the convolutions and that is where they see the most stress when the wheels are turned and the convolutions are opened up.. I have seen two piece zipper boot designs that will go over the existing boot but I have not used them.

[airmike]

I have seen those replacement boots in the past, but not any more. I think they have got people just changing the entire assembly for ease and quickness. I have done the boot before and you do need the crimping tool for the clamp. I think the original cv joints are indestructible if you keep them greased. Good luck if you do the boot, and let us know how it turns out.

[lothos]

I was able to get an alignment today Car drives nicely, no more pulling to the side, steering wheel is straight and the car no longer pulls to the side when I apply the brakes. I didn't hear any front end noises on the short drive home, either. I think maybe the noises I was hearing before was the front end shifting around under there from the bad alignment.... I'll keep an eye on it.

I have seen those replacement boots in the past, but not any more. I think they have got people just changing the entire assembly for ease and quickness. I have done the boot before and you do need the crimping tool for the clamp. I think the original cv joints are indestructible if you keep them greased. Good luck if you do the boot, and let us know how it turns out.

That's disappointing, I'll have to check the dealers around here or call Rockauto and see if I can find a boot somewhere. There were half a dozen aftermarket options on rockauto, but no way to tell if they're good quality or not. From the assistance here and what KHE said I'd like to try to save the current axle. Will definitely post back when I figure something out.

[rcirobin]

I just checked gmpartsdirect.com, they have the OEM boots for 25.74. I would assume any GM dealer would have or could order them.

[lothos]

I just checked gmpartsdirect.com, they have the OEM boots for 25.74. I would assume any GM dealer would have or could order them.

Hey, thanks for the help I'll check there and call a few dealers.

[lothos]

Haven't had a chance yet to call around for that boot.

My o2 sensor arrived and I put it in last night. It was a pain to change, had to call my buddy over for some help. Old sensor snapped in half, and the bolt started to strip. We got it changed out, though.

I wasn't getting any codes, but noticed I was only getting about 10-11 MPG in the city. Also didn't get any codes when the sensor was broken and we heated the engine to make for easier O2 sensor removal. I read that this model relies a lot on the O2 sensor so decided to replace it to fix my low gas mileage. I haven't disconnected the battery or done an idle learn yet.

Before O2 sensor change: 10-11MPG city. ~19MPG highway.

Will post the After MPG in a few days.

I suspect that I have a bad FPR. Getting some hard starts and it seems to be worse when the engine is warm but also sometimes when cold. I think it's under my air cleaner assembly but wasn't confident enough to just start pulling hoses off to check for dripping fuel

I'm also getting a slight rough idle. It happens cold but seems worse when hot. There is vibration at idle. There is also a small hesitation when accelerating gently from idle. Also if I'm idling and just take my foot off the brake, and let the car move forward by itself the movement is jerky, which is worse going up an incline. Medium/heavy acceleration seems fine with no hesitation that I can tell. Cruising seems fine.

I've replaced plugs/wires, cap/rotor, air filter, fuel filter, and the O2 sensor was done last night. The cat has been replaced but not by me.

Haven't done FPR, fuel injectors, MAP sensor. The engine also wasn't timed but my buddy marked the cap/rotor and used that to put on the new ones.

Any suggests are appreciated I would like to measure the resistance of my fuel injectors but am unsure where the harness is located to do so.

[lothos]

I should add that the rough idle started about 2 weeks ago maybe? After filling up with 87 instead of 91 octane. Thought the octane was too low or I got some bad gas but I've filled up twice since then with 91.

I was also digging around under the hood trying to diagnose the gurgling noise from the heater core and might have disturbed something. I've checked the vacuum lines and such under there and everything looks OK although I'm still a newbie and could very well have missed something. I'm also still hearing the gurgling noise last time I checked which was last week. I DID have to put some coolant in the overflow, but I checked it cold when it says to check hot. It was maybe 1/4 inch low, if that, and hasn't budged since then.

Also around this time I was dealing with my security ignition bypass and had disconnected the battery.

[lothos]

Good news

Idle started getting better on the way home from work today. When I got home I disconnected the battery for about 5 minutes. Now the idle is a ton better. Yesterday, the seat belt on the passenger seat would vibrate and move. Today, it doesn't.

I'd say the idle is 95% better now. I'm not sure if a passenger would be able to tell but I can still feel that's it very slightly off. The hesitation on light acceleration is a lot better now, also.

I'll give the car a couple days to learn it's idle and see how it does.

[the gold2]

Good news

"Yesterday, the seat belt on the passenger seat would vibrate and move. Today, it doesn't."

hehe I thought the belt was moving literally on its own... spooks!

I'll give the car a couple days to learn it's idle and see how it does.

The idle learn procedure might help also.

For future reference your dash DTC data can display injector behavior, left bank /right bank, individual injectors, Oxygen sensors and other good data.

It is in your service manual.

p.s. did you ever post the pics and procedure in your other thread regarding the pas key bypass??

[lothos]

The idle learn procedure might help also.

For future reference your dash DTC data can display injector behavior, left bank /right bank, individual injectors, Oxygen sensors and other good data.

It is in your service manual.

p.s. did you ever post the pics and procedure in your other thread regarding the pas key bypass??

I haven't dived into the DTC data yet, it's a little more cryptic than the STS was. I'll definitely check that section out though, thanks for the tip. So far I'm able to pull codes and clear codes, haven't looked at the other functions yet. I'll see if I can find the idle learn procedure and give that a shot.

I haven't done the writeup yet I was actually working on it Sunday, but I looked at the pictures I took and they didn't turn out so well. I'm planning on taking some new photos soon, though. I'd like to have it done before new years, but if you need help with it before then I'd be more than happy to walk you through it.

[KHE]

The hesitation off idle could be plugged EGR tubes - have you cleaned them out?