Fluctuating temp gauge, losing coolant 01 5.0

[shadowless127]

Weird problem I've been having for the past 5-6 weeks. I've always had a slight coolant leak since I got the car but it was never a big deal. Cut to like a week before Christmas and I notice my temp gauge is higher then usual. Hook up my scanner and see that the temp is 214. So I see that my coolant level is low, so I top if off, problem goes away, kind of. The temperature now fluctuates (confirmed by gauge and OBDII scanner) intermittently. It will stay normal, then drop down to under 190, then creep back up. Sometimes It will be at normal temp, i'll stop at a light then when i take off from the light the temp plummets and the gauge drops all the way to the bottom line and then slowly creeps back up. It's done this a few times while underway as well.

Temp never goes above 214, which I know is not technically overheating, but considering I don't have an LS engine in this, I'd like it to stay under 200 lol

I also seem to be losing more coolant then I previously had, but I can't find a puddle and it's not coming out of my tailpipe or going into my oil.

I've noticed zero difference in performance or how it runs.

I'm guessing my first steps should be new radiator cap and a coolant system flush?

 

[1998Exp]

I would start with finding the source of the leak. A pressure tester, which you can rent for free from most auto stores will help. Don't forget to look inside the plastic stone guard under the radiator.

...
I also seem to be losing more coolant then I previously had, but I can't find a puddle and it's not coming out of my tailpipe or going into my oil.
...
I'm guessing my first steps should be new radiator cap and a coolant system flush?

 

[koda2000]

my guess is you have bad (leaking) radiator. the temp dropping and then rising is an indication of low coolant level in the radiator. when this happens the overflow tank remains full, because the system is no longer sealed and is sucking in air to replace the lost coolant, rather than pulling coolant from the overflow tank.

it's pretty common for the plastic radiator tanks to loose their seal to the aluminum core.

 

[shadowless127]

Well that sucks. How do you guys feel about JY radiators?

 

[koda2000]

Well that sucks. How do you guys feel about JY radiators?

well, you first need to verify that that's the problem, but considering what a wrestling match it is to install a radiator in a 5.0 (problem is a/c condenser mounts) I'd install a new one.

 

[shadowless127]

well, you first need to verify that that's the problem, but considering what a wrestling match it is to install a radiator in a 5.0 (problem is a/c condenser mounts) I'd install a new one.

Obviously

I have mechanics for the install. I live in the North East and the weather has been horrendous lately; there is no way I'd be doing this job, or any job on the car sans topping off fluids, in this weather. Today is a warm day at 34F

 

[shadowless127]

Well, here's something weird. Just went out to top off the coolant level because the temp was hanging over 200 a bit for a little while when I was out before. Turns out, the radiator is full. Last time I topped it off was 10 or so days ago and it doesn't appear it's lost any coolant.

I'm wondering if it's a flow problem compounded by a leak somewhere?

 

[shadowless127]

Think I've narrowed down the issue. It's either my fan clutch, or water pump. Drove to work today with my OBDII scanner hooked up displaying live info and it seems the car gets warm when at a stop but cools down while driving. So I'm thinking either my fan clutch is shot, or the water pump needs to be replaced because it's not pushing enough water through at idle RPMs.

Will check the fan clutch when I leave work today, and if it's spinning freely I'll go ahead and have that replaced. If not, I'm going to have the water pump replaced.

 

[SoNic67]

When engine is cold, open the radiator cap. It should have fluid all the way to the top - if not, the radiator lost it's seal.

The clutch fan - you should be able to spin it cold by hand with some resistance (it won't keep spinning by itself). At hot, with engine running, if you put a newspaper in the blades, that should not stop from spinning. Careful, not too thick, it might break an already cracked plastic fan.
Also, on a bad fan, you shouldn't have any temp issues while driving on highway with 55-65 mph - air flow by itself should be enough for that small engine load.

Bad news: I had a similar issue on my Sable. Ended up being a cracked impeller (made of plastic) in my water pump that was probably engaging now and then until finally gave out completely - lucky I was close to home.

 

[shadowless127]

When engine is cold, open the radiator cap. It should have fluid all the way to the top - if not, the radiator lost it's seal

The clutch fan - you should be able to spin it cold by hand with some resistance (it won't keep spinning by itself). At hot, with engine running, if you put a newspaper in the blades, that should not stop from spinning. Careful, not too thick, it might break an already cracked plastic fan.

Bad news: I had a similar issue on my Sable. Ended up being a cracked impeller (made of plastic) in my water pump that was probably engaging now and then until finally gave out completely - lucky I was close to home.

I'm going to replace the radiator cap anyway as it's the OE one that is now 15yrs old.

I'm going to do the free hand thing with the fan and see if it just spins freely, simple enough to do. Thankfully it's been hovering around freezing for the past while so the engine hasn't gotten near overheating, just hot. I don't have cooling issues when underway.

I'm not too concerned about whether it's one issue or the other because this is going to cost me ~$200 either way so it is what it is.

There goes buying some new computer parts lol

 

[shadowless127]

fan clutch is fine, fan turns with some resistance. Going to schedule to have the water pump replaced.

 

[SoNic67]

I think that in our 5.0L the impeller is metallic, sometimes it is rusting.

PS: This is what I found in my case (Taurus DOHC engine):

 

[shadowless127]

Dropped it off at the shop and while I was waiting for my ride they had already put it up on the lift and started looking at it. He said my radiator is leaking, he looked at the water pump and it looked fine.

So I'm getting the radiator, t-stat, t-stat housing, and gasket replaced for $300 out the door.

 

[BustedKnuckles24]

Damn good bargain with labor included. Good luck.

 

[shadowless127]

Damn good bargain with labor included. Good luck.

Yeah. I don't think he's double dipping me on the labor like a lot of places. Found this place online a while back and figured I'd give it a shot. Nice clean shop, nice clean waiting room with big screen and leather couches. Garage area is probably the cleanest garage I've ever seen with newer lifts.

Should be done by end of day, so we shall see.

 

[shadowless127]

Problem still exists but temps seem lower, I guess since there's no clog in the radiator now.

I'm going to assume the impeller in the water pump is not in good shape and just isn't pushing water through fast enough when at idle.

What are the odds of a bad temp sending unit?

 

[koda2000]

did you check your fan clutch?

 

[shadowless127]

did you check your fan clutch?

Here's what it looks like when I try to spin the fan by hand. Seems like enough resistance to rule out the fan clutch.

 

[koda2000]

Here's what it looks like when I try to spin the fan by hand. Seems like enough resistance to rule out the fan clutch.

ER1gpP7bK54

was the engine at operating temp in the video? the hotter the engine/radiator the stiffer the fan should be to turn.

 

[shadowless127]

was the engine at operating temp in the video? the hotter the engine/radiator the stiffer the fan should be to turn.

No, engine was off, had been sitting for about 3.5hrs.

Also, I did a little test tonight. If I sit with the car in gear and the revs are about 500-650, I can see the coolant temp start to rise on my scanner. However, if I hold down the brake and bump the revs up over 1000rpm I can see the temp start to fall.