Cooling System Questions

[Benjamin4456]

Alrighty, the 87 LXi I picked up a few months ago has been doing pretty well (already put over 7k on it) but some recent events have me wondering about the cooling system.

First off, the gauge always seems to get pretty high before the fans turn on. As in, borderline concerningly high. I'll attach a photo below that I took just after they finally kicked on (the needle was just starting on its way down at the time). When driving normally the gauge sits around 45% all the time. Only when I've been stopped for a while does it begin creeping up and eventually get so high.

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Second, every time I switch the temp controls from cold to hot after it's been sitting a while (ie. in the mornings), I briefly get a lot of gurgling sounds coming from the heater core. I've never known a heater core to accumulate air but not leak so....? Thoughts? Is this somehow normal for these cars? Could it be sucking in air from somewhere as it cools down?

Today I was driving around and occasionally heard some coolant gurgling noises when accelerating away from a stoplight (this was also after it had gotten quite hot and the fans kicked on a couple times). Not quite sure what to make of that.

Lastly, I recently fixed an oil leak on the distributor and in the process bumped the TW sensor wiring. Everything still seems intact but it threw code 6 a couple times and I've noticed that if I wobble the connector it can change the idle speed, and if cold, it will also make something click very fast in the vacuum control box (cold advance solenoid I'm guessing?). Just picked up a replacement sensor but haven't installed it yet. Open to ideas if anything comes to mind there.

Anywho, I know it's a bit of a jumbled list but I'd appreciate some ideas if anyone has them. Thanks!

[Benjamin4456]

Most of the above questions still stand although I have now replaced the TW sensor. Darn easy sensor to replace too, that was great.

So far so good but I'll keep an eye out for the PGM-FI light and any more of that clicking from the vacuum control box. I checked the harness side of things and the connector and wiring seems to be in good shape. The old sensor however was not in great shape - the connector was starting to fall off.

Still curious if anyone has thoughts about the high temp gauge/fan-on set point and the coolant noises.

[RI86DX]

Have you bled the coolant system? Could be a shit ton of air in it.

[Oldblueaccord]

I think your car is over heating.

One thing you can do is use an IR gun on the thermostat housing and see where your temps are. Skip the gauge.

Ill check mine out when I drive it this week.

[Benjamin4456]

Haven't bled the cooling system but that could definitely be it. I did pull off the radiator cap yesterday and it wasn't quite full so I topped it off. No change as of yet except less gurgling but we'll see. Given the fan switch is on the bottom of the rad it seems like it shouldn't be affected by a little air in the system though. I also checked the coolant concentration and it's plenty fine with the water/glycol ratio.

I'll check the t-stat neck with an IR thermometer when I get home today, good idea. What range am I looking for when the fans kick on?

Also have a fan switch on order on the chance that might be it. Figure it's old enough that it should probably be replaced anyway for peace of mind.

If it comes to it, do I need to be worried about damaging the drain on the radiator? Are they known to get brittle or no longer sealing with age after being messed with?

[Oldblueaccord]

https://youtu.be/sZkukZFm_gg

[Benjamin4456]

Thanks for making that video! It definitely seems I'm overheating a bit after checking things over with my IR gun. It's much colder here than where you are (so it took a while for things to get hot) but the fans didn't kick on until the top tank of the radiator was approaching 220F. The upper and lower hoses are around the same temp (peaked around 205F on my thermometer) so it doesn't seem to be a flow issue. I'm still leaning towards the fan switch being the problem, so I might give that a shot pretty soon.

Normal running temp shows ~180F on both hoses so I think the t-stat and the rest of the cooling system is fine, it's just the fans not coming on when they should.

Just wanted to check again before I do drain the coolant and replace the sensor, do I need to be worried about the draincock on the radiator? Or anything else for that matter. Really don't want to break anything.

[Oldblueaccord]

Thanks for making that video! It definitely seems I'm overheating a bit after checking things over with my IR gun. It's much colder here than where you are (so it took a while for things to get hot) but the fans didn't kick on until the top tank of the radiator was approaching 220F. The upper and lower hoses are around the same temp (peaked around 205F on my thermometer) so it doesn't seem to be a flow issue. I'm still leaning towards the fan switch being the problem, so I might give that a shot pretty soon.

Normal running temp shows ~180F on both hoses so I think the t-stat and the rest of the cooling system is fine, it's just the fans not coming on when they should.

Just wanted to check again before I do drain the coolant and replace the sensor, do I need to be worried about the draincock on the radiator? Or anything else for that matter. Really don't want to break anything.

its old plastic I would be wary it probably is brittle.

You can force the fans on by engaging the AC and first fan speed. If you dont want to use AC or the compressor is bad you can pull the compressor clutch fuse or unhook the compressor clutch. I think its 20 amp fuse under dash fuse panel.

My fans came on just as I shut the hood after that video was taken.

[Benjamin4456]

Sounds good, I'll probably take a look at it this weekend. Heck I might even try to swap sensors without draining the coolant, we'll see.

[ShiRen]

The fans will come on super late, it's incredibly insensitive. Supposed to be 195 degrees but I wouldn't put your money on it. Plus it should be on the cold side

You don't need to drain the coolant to replace it but you will make a huge mess. I wouldn't worry about the drain if you do though, just don't go ape on it. I think I did damn near strip my original one, it still sealed

[Benjamin4456]

Sounds good, thank you. I'll be sure to update whenever I have a chance to do the swap.

[Benjamin4456]

Well I replaced the sensor and not a whole lot changed. It still usually waits until the gauge is fairly high before kicking on, although this time I measured the radiator tanks and hoses closer to 190F when that happens. The after-shutdown-fan also isn't running so I don't think it's actually all that hot (I know said feature works as it has happened a couple times in the past).

I also read through the manual and supposedly anywhere in the white section of the gauge (basically the full range) is technically ok, and only when it's in the red should you worry. I'm not a huge fan of that logic but eh, it's an old car with so-so gauge accuracy and it's what the manual says so...

For now I think it's probably fine but I'll keep an eye on it.

Oh, also I didn't drain the coolant to swap sensors and it really didn't spill much. Definitely easier than draining the whole thing.

Cheers.

[RI86DX]

Bleed the system using the bleeder bolt near the tstat, it's what got rid of it for me.

[conozo]

The dash coolant guage on these cars typically just at half way when warmed up. They dont swing that much.

Make sure your coolant hoses are correct. The hose that connects to the thermostat housing should go to the top of the radiator. I've seen several get them switched around and its near impossible to bleed.

[Benjamin4456]

Fair enough, I'll take another look at it next chance I get.

For what it's worth the gurgling in the heater core is gone now that I've messed with the cooling system some. It also seems full since it's pushing coolant over into the overflow consistently but I'll still check the bleeder.

Also just making sure understand correctly, do you use the bleeder just when filling or when the engine is running too? I've seen both ways suggested. The FSM would indicate just to use it when filling and then close it before starting the engine but others don't seem to agree.

[Oldblueaccord]

Fair enough, I'll take another look at it next chance I get.

For what it's worth the gurgling in the heater core is gone now that I've messed with the cooling system some. It also seems full since it's pushing coolant over into the overflow consistently but I'll still check the bleeder.

Also just making sure understand correctly, do you use the bleeder just when filling or when the engine is running too? I've seen both ways suggested. The FSM would indicate just to use it when filling and then close it before starting the engine but others don't seem to agree.

On the bleeder short answer is both.

I use it running/up to temp then bleed. Just like you would brakes.

[ShiRen]

Doesn't matter as long as you get it hot and open it until it stops sputtering. That's what you have to do in the end either way.