1991 Lx 5.0 Running Too Hot?

cdurbin · Aug 1, 2012

I'm having some cooling issues. The car has an oversize aluminum radiator which was on the car when I bought it last week. I've changed out the thermostat and put in a 180° and also replaced the temp sending unit. I did notice that it had almost all coolant in it so I drained some of it and put in 50/50 water along with a bottle of water wetter. From what I can tell, the fan clutch is good and the fan itself looks good too. This morning I got stuck in traffic and the temp needle rose all the way up to the notch just below the red. I wasn't even running the air. also when I got to the office, I popped the hood and shot the thermostat housing with a infrared thermometer and it was reading 210° which doesn't seem that hot for these cars.
What am I missing?

88LX5.Oh · Aug 1, 2012

Does the car have underdrive pulleys? I've heard that with underdrives, a car will over heat in stop and go traffic but will do just fine going down the road (not sure if this is entirely true). Also check to make sure your radiator cap is good and holding pressure

cdurbin · Aug 1, 2012

Not sure on the pulleys but I just replaced the cap too.
How can you tell if it has underdrive pulleys or not?

stykthyn · Aug 1, 2012

Have you burped the coolant by jacking up the front of the car and running it with the cap off to let all the air out?

cdurbin · Aug 1, 2012

I ran it with the cap off until it reached operating temp and the thermostat opened. Once it opened the water level dropped and I filled it back up.
I also ran it with the heat on high and drove it down the street and then rechecked the level and it was good.
I did not jack it up though. That's a new one on me. I've never heard that before. I'm wondering if the water pump is about to kick it.

stykthyn · Aug 1, 2012

no. if you didnt lift the front end the radiator will not be the high point and you will still have air trapped in the system. lift it about 18-20 inches and run it until the t-stat opens again. You still have air trapped in the system. Make sure the heater is on as well.

cdurbin · Aug 1, 2012

well alright then: learn something new everyday. I'll give it a shot. thanks for the info!

cdurbin · Aug 1, 2012

Well, I'm lost. I took it up to a local shop that I trust and had them hook it up to the machine. They let in run for 30 minutes and the temp stayed right at 195°.
I drove it back to work and then home this afternoon in traffic and it never got much higher than a little over half way. I'm wondering if my fan clutch is going bad or maybe my stock temp gauge.

88LX5.Oh · Aug 1, 2012

Spin the fan with your hand. When you do this, is there tension or does the fan spin easily? If it spins easily, then the fan clutch is going out.

cdurbin · Aug 1, 2012

88LX5.Oh said:
Spin the fan with your hand. When you do this, is there tension or does the fan spin easily? If it spins easily, then the fan clutch is going out.

I tried that and it has tension on it. I'm not sure what else it can be.
It ran warm as hell this morning (almost in the red) when the temp outside was at least 15° cooler. Then this afternoon it stayed around half way.
I just replaced the sending unit.

cdurbin · Aug 1, 2012

I don't know if this means anything but when I first get in the car in the morning and fire it up. The temp gauge rises to half way before I even get a mile from my house. That seems really fast to me. Like I said, Maybe the stock gauge is going out. I plan to pick up an Autometer gauge and install it. I know the factory gauges can be way the hell off. It still makes me nervous to see that needle climb toward the red. I've only had this baby for a week and I'd hate to blow it up.

2000xp8 · Aug 1, 2012

cdurbin said:
I don't know if this means anything but when I first get in the car in the morning and fire it up. The temp gauge rises to half way before I even get a mile from my house. That seems really fast to me. Like I said, Maybe the stock gauge is going out. I plan to pick up an Autometer gauge and install it. I know the factory gauges can be way the hell off. It still makes me nervous to see that needle climb toward the red. I've only had this baby for a week and I'd hate to blow it up.

You have air in the system, the quick rise in temp tells the tale. An air pocket prevents the coolant from circulating.

While i never really jacked my car up (something that is more common with modulars), i always did let it run for a really long time before i put the cap back on.

With that said, i'm a temperature watcher, almost addicted, so IMO still get the autometer, use a mechanical full sweep gauge.

cdurbin · Aug 2, 2012

2000xp8 said:
You have air in the system, the quick rise in temp tells the tale. An air pocket prevents the coolant from circulating.

While i never really jacked my car up (something that is more common with modulars), i always did let it run for a really long time before i put the cap back on.

With that said, i'm a temperature watcher, almost addicted, so IMO still get the autometer, use a mechanical full sweep gauge.

So how long would you recommend I let it run to be sure there is no air in the system?

I drove it to work this morning and it stayed at the half way point. I'm going to go ahead and try to make sure I get all the air out of the system this weekend. I'm going to pick up a good mechanical temp gauge as well. Thanks

DocG · Aug 2, 2012

I would always use this tool that basically is like a funnel that seals onto the cap opening. Would add coolant into that funnel and let it run while squeezing the hoses. You will see all the air burp out. Almost have to have that extra coolant on top sp the air bubbles out and doesn't get sucked back into the system. Always worked good for me.

2000xp8 · Aug 2, 2012

If the gauge is working properly, half way up still sounds a bit high to me for a 180 thermostat and a big aluminum radiator.

I usually let mine sit for at least 20 minutes.

For an accurate t stat i always use the mr. gaskets 180, autozone and pepboys usually have them.

I liked my car to run 180 degrees in all conditions.

jsw81 · Aug 2, 2012

Do you have a coolant expansion tank? When I bought my fox, the previous owner had an aftermarket aluminum radiator in it. The stock expansion tank was gone, since there was no room for it. My temp would fluctuate a lot and get up into the red sitting a little in traffic. I picked up a universal tank and now it works without issue. Just a thought.

cdurbin · Aug 3, 2012

jsw81 said:
Do you have a coolant expansion tank? When I bought my fox, the previous owner had an aftermarket aluminum radiator in it. The stock expansion tank was gone, since there was no room for it. My temp would fluctuate a lot and get up into the red sitting a little in traffic. I picked up a universal tank and now it works without issue. Just a thought.

It's got the expansion tank on it.

cdurbin · Aug 4, 2012

Today I drained the entire system, replaced all the hoses, replaced the fan and fan clutch.
Refilled and let it run in the driveway with the font end jacked up about 18" or so.
After all that the thing still got up to 210 at the thermostat housing when I shot it with a thermometer.
I can see the water flowing in the radiator so I think the water pump is good. Now what?
I'm trying to figure out if the thing has underdrive pulleys on it. I've read that will cause it to run hot while sitting in traffic. If don't get it figured out soon I'm just going to take it somewhere and have people smarter than me look at. I can't take much more of this riding around with the A/C off in fear of the thing overheating...

2000xp8 · Aug 5, 2012

Get yourself an oil pressure and water gauge setup. Full sweep mechanical on both.
The money spent is worth the peace of mind.
I'm not sure how accurate reading the pipe temp is. I'm not saying it's inaccurate, it's just not how i would check temps.
If it doesn't leak, the water pump is likely fine.

While i'm not the biggest fan of underdrive pulleys, many people get buy without cooling issues with them, especially if they have a bigger radiator.

cdurbin · Aug 5, 2012

2000xp8 said:
Get yourself an oil pressure and water gauge setup. Full sweep mechanical on both.
The money spent is worth the peace of mind.
I'm not sure how accurate reading the pipe temp is. I'm not saying it's inaccurate, it's just not how i would check temps.
If it doesn't leak, the water pump is likely fine.

True. I bought a mechanical temp gauge as well as a mechanical oil pressure gauge. Just waiting on one to come in. I had to order it.
I designed a gauge panel to fit underneath the radio. I wanted it to look clean and "factory". I take some pics once I get it all hooked up.
Thanks for the input

1991 Lx 5.0 Running Too Hot?

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