2 mysteries - anti-freeze and oil pressure

[efnfast]

2 mysteries I've been chasing around, curious if anybody has any input

1 - anti-freeze leak on the driver's side

If I park the car for 3 weeks and the weather outside is > 32*F, the underside is bone dry.

If I park the car for 3weeks and the weather ouside is < 32*F, I leak about 1/4oz of antifreeze. The leak is on the driver side - I find green droplets on the oil pan and oil filter. Nothing on the passenger side. No matter where I look (waterpump, intake, heads, etc.. etc...) there is no obvious trail anywhere. If I start up the car and let it idle in the cold, no leaks. Pressure test in the cold - no leaks.

The nearest I can figure is that there's some seal that is not happy with the cold weather. It's a moot issue (since it's only if I let it sit for weeks on end in the winter) but a curiosity to me if anybody has experienced something similar to this.



2 - Oil pressure fluctuations

If oil temp < 150* my oil pressure gauge is rock solid when I'm driving and when I'm idling.

If oil temp > 150*, my oil pressure gauge is rock solid when driving, but if I just sit and idle sometimes the needle twitches around, usually between 25psi and 32ish psi (just a rough guess since the area between 25psi and 50psi is not marked on the autometer ultralite gauge)

When the needle is twitching nothing unusual is happening (e.g., bad idle, etc...). Everything is perfectly normal.

It's not an issue with the idle or the cam because sometimes the needle twitches, sometimes it's rock solid and doesn't twitch an inch. Totally random, but when it's twitching there's nothing unusual happening, and nothing I can tie it to (i.e., it doesn't happen right after going WOT, or after a hard break, or anything memorable).

I ~think~ it might be the oil pressure sending unit - oddly I've read a lot of threads where the units are fine when oil temps are cool, but when they warm up the sender stops working. Although mine is working, just twitchy at idle randomly (i.e., sometimes it twitches, sometimes it doesn't).

Next time I change the oil I'll change the sender, but if that doesn't work I'm just wondering if there's any other reasons for a twitchy oil pressure at idle when the oil temp is warm? I would imagine if it's pointing to a failing component (e.g., oil pump) then I would have issues when driving, not just a twitchy gauge needle at idle sometimes?

[Wayne Presley]

I have fixed a problem like that by soldering a ground wire to the case of the sender.

[efnfast]

The weird thing is year 1 it was perfectly fine (no twitching), it just started up last year. You'd think if it were a grounding issue it woul dhave done it since day 1, not to mention it would do it all the time, not just at idle when warmed up?

[gwnorth]

Using an '89 donor engine, I had a similar antifreeze leak when the car sat in an unheated garage during my build: garage only heated when I was working. Installed a new waterpump and altho better, it still sometimes seems to weep antifreeze a little when left standing in the cold. I suspect the seal is stiff and gets a flat spot which goes away as soon as it runs.

[Bob Cowan]

The antifreeze leak is most likely a freeze plug. The plug and the block are differant materials, and tend to expand and contract at differant rates. Eventually, it's going to fail completly. Maybe in a month, maybe in a decade. I'd figure out which one it is, and replace it.

As the oil heats up, the viscosity drops. That's what's supposed to happen. When cold, the oil pressure is high enough to open the relief valve in the pump. Once the viscosity drops with the heat, there's not enough presure to open the valve, and now the pressure fluctuates a little at idle.

Since the pressure is still good, that's evidence of the perfect oil viscosity. You could "fix" it, by increasing the viscosity. But you'll waste energy moving that oil around. All it will do is make you feel all warm and fuzzy when you look at the gauge.

[efnfast]

The antifreeze leak is most likely a freeze plug. The plug and the block are differant materials, and tend to expand and contract at differant rates. Eventually, it's going to fail completly. Maybe in a month, maybe in a decade. I'd figure out which one it is, and replace it.

As the oil heats up, the viscosity drops. That's what's supposed to happen. When cold, the oil pressure is high enough to open the relief valve in the pump. Once the viscosity drops with the heat, there's not enough presure to open the valve, and now the pressure fluctuates a little at idle.

Since the pressure is still good, that's evidence of the perfect oil viscosity. You could "fix" it, by increasing the viscosity. But you'll waste energy moving that oil around. All it will do is make you feel all warm and fuzzy when you look at the gauge.

In terms of the freeze plugs I've examined them (and everywhere I could think of that coolant could be) and there's no evidence of it coming from them (although there's no evidence of it coming from anywhere, hehe).

I don't think it's from them because the anti-freeze drip is usually dripping off the oil filter and the front crank pulley (it pools at the bottom of the pulley and drips off) ..... because of the location (very front of the engine) my guess is something with the waterpump, and I'd kind of agree with gwnorth - something with the seal developing a flat spot in the cold.

In terms of the oil pressure, I can understand what you're saying but the reason I keep pondering it is because, up until a year ago, the gauge did not twitch at idle when warm. So that's a mystery to me (which kind of makes me think the pressure sender because everything else is perfectly fine)

[patpur]

I had a similar problem when I first got my car. Checked it out thoroughly, spent literally hours going over it. I didn't want to buy a car that was leaking fluids. Got it home, took a ride around the block, pulled in the garage and anti freeze on the floor. Have you checked your manifold gaskets (intake where it bolts to the heads)? Mine were leaking, ever so slightly, in the front. It would puddle behind the water pump, kinda hard to see and then when the puddle got big enough it dripped on the floor. I don't know how many times we went over the engine and didn't see it. My mechanic said its a common problem. Hope this helps.

[efnfast]

I had a similar problem when I first got my car. Checked it out thoroughly, spent literally hours going over it. I didn't want to buy a car that was leaking fluids. Got it home, took a ride around the block, pulled in the garage and anti freeze on the floor. Have you checked your manifold gaskets (intake where it bolts to the heads)? Mine were leaking, ever so slightly, in the front. It would puddle behind the water pump, kinda hard to see and then when the puddle got big enough it dripped on the floor. I don't know how many times we went over the engine and didn't see it. My mechanic said its a common problem. Hope this helps.

Yep - and remember I have 0 leaks in the spring/summer/fall, only when temps drop below 32*F and it sits for 3-4weeks.