27 replies to this topic

[Justin Fowler]

Alright I got a question. I seem to be getting a lot of bubbles/overflowing when my radiator cap is off and the car is at idle. Is it normal for the car to be overflowing coolant at idle? If so how much overflow is acceptable?

Basically my temp gauges have been throwing me off. I have had 2 mechanical AutoMeter gauges read my coolant temp at around 200-210F at idle but my VDO electric gauge reads maxed out at 250F. I figured I had air in the system so today I jacked up the front end and started to burp the system.

Well at idle my coolant seems to just overflow. Around 210 (when my fan kicks on) it overflows a lot then shoots back down like it had lost the air. I would fill it up again and it would do the same exact thing. I did this for quite some time until I decided to hold my idle up a bit, around 2000rpms. Well holding it there would make my coolant shoot out of the radiator like a volcano after a few moments. To me this seems like I am getting compression in my cooling system like a bad head gasket or a cracked head/block.

What do you guys think? My head gasket looks alright. It is a 3 layer gasket so I know it could be leaking in between and not noticeable. Also my head shows signs of my new valve seals leaking so that explains my white smoke on cold starts. I figure I have one of the three blown or cracked. Not quite sure where to go from here, I am clueless.



When I loosed up my manifold to remove the head I had noticed coolant/oil run from under the #1 side. Pics are bad but #1 cylinder looks cleaner than the rest and that usually indicates coolant in the cylinder. #4 (far left) is wet because I think it got oil/coolant on it when I was turning the head over but I am not 100% sure on that


#1 piston is on the far right. I had noticed when I turned the motor over a few times that #1 and #4 cylinders had a small white ring around the walls. To me it seemed to be a mixture of coolant and oil. No signs of any cracks

[DES4]

You'd need to first confirm that what's happening is combustion gases in the coolant; it's a little late to check it if you've got the head off, however. The best test is with a litmus dye test; with the engine running, it uses a blue fluid that turns green if CO is present at the radiator cap neck, and it's pretty much conclusive. A smog sniffer can also be used, as well... again, having pulled the motor apart, it's a little late for that.

It's unlikely, if you've got coolant entering the cylinders, that it'll affect all four cylinders equally, so you'd expect one or two cylinders to stand out as problem cylinders. You seem to have picked out a few areas that may indicate such; depending on the severity of the leak, the problem cylinders usually look pretty clean, comparatively speaking. If it were the head gasket leaking, there might be a sign of the issue, although it might take some pretty close scrutinizing of the gasket/mating surfaces to pick it out. Spark plugs can also indicate which cylinder(s) have an issue; look for a standout difference in color/buildup.

Having not performed the litmus test, I'd say the symptoms do indicate combustion gases in the cooling system. If not the head gasket, I'd take the head for magnafluxing, as that would be more likely than water entering through the cylinders. Not too many ways for coolant to enter beyond that...

[exninja]

Could there be a clog or restriction in the radiator or lower hose? Maybe that's causing backpressure in the top of the radiator causing the overflow. Just a guess...

[Justin Fowler]

You'd need to first confirm that what's happening is combustion gases in the coolant; it's a little late to check it if you've got the head off, however. The best test is with a litmus dye test; with the engine running, it uses a blue fluid that turns green if CO is present at the radiator cap neck, and it's pretty much conclusive. A smog sniffer can also be used, as well... again, having pulled the motor apart, it's a little late for that.

It's unlikely, if you've got coolant entering the cylinders, that it'll affect all four cylinders equally, so you'd expect one or two cylinders to stand out as problem cylinders. You seem to have picked out a few areas that may indicate such; depending on the severity of the leak, the problem cylinders usually look pretty clean, comparatively speaking. If it were the head gasket leaking, there might be a sign of the issue, although it might take some pretty close scrutinizing of the gasket/mating surfaces to pick it out. Spark plugs can also indicate which cylinder(s) have an issue; look for a standout difference in color/buildup.

Having not performed the litmus test, I'd say the symptoms do indicate combustion gases in the cooling system. If not the head gasket, I'd take the head for magnafluxing, as that would be more likely than water entering through the cylinders. Not too many ways for coolant to enter beyond that...

I have done a dye test. It was basically impossible to do so. The radiator had water barely flowing over the top fins and when I was testing it would just shoot up my tester and make the test useless. I tried several times, each time coolant would shoot straight into my tester a second or two after it would start bubbling.

#1 cylinder definitely was cleaner than the rest. When I removed my exhaust manifold I had noticed "water" drop from the #1 cylinder which made me believe water came out of the exhaust runner.

Big question is if it is "normal" for a cooling system to overflow coolant at idle. I know the system will burp usually around when the cooling fan kicks on but mine seems to be much more than a usually cooling system. Even at idle I have bubbles coming out of the radiator like crazy. I know there is not that much air in the system. According to my temperatures the car has never overheated so I don't think my head is warped. (was at the machine shop 300ish miles ago) My coolant temps are around 180-200 at idle according to our temp gun and my gauges.

[Keith Novak]

It's not normal. I'll run the car with the cap off for a while to burp it that way. If that much combustion gas is blowing into the radiator, do you find any signs of oil in the coolant when you drain it?

Looking at the pictures, something is missing on each end. There's normally a thin hollow dowel that sticks out of the engine block and into the head, one front one back. Did you pull those out for the pic or are they not installed in the engine?

[Justin Fowler]

It's not normal. I'll run the car with the cap off for a while to burp it that way. If that much combustion gas is blowing into the radiator, do you find any signs of oil in the coolant when you drain it?

Looking at the pictures, something is missing on each end. There's normally a thin hollow dowel that sticks out of the engine block and into the head, one front one back. Did you pull those out for the pic or are they not installed in the engine?

Doesn't seem to have oil in the coolant or coolant in the oil.

I just checked, I have a dowel in the rear of the block but not the front. I must have misplaced the front when I did my engine rebuild.

[James York]

I have done a dye test. It was basically impossible to do so. The radiator had water barely flowing over the top fins and when I was testing it would just shoot up my tester and make the test useless. I tried several times, each time coolant would shoot straight into my tester a second or two after it would start bubbling.

#1 cylinder definitely was cleaner than the rest. When I removed my exhaust manifold I had noticed "water" drop from the #1 cylinder which made me believe water came out of the exhaust runner.

Big question is if it is "normal" for a cooling system to overflow coolant at idle. I know the system will burp usually around when the cooling fan kicks on but mine seems to be much more than a usually cooling system. Even at idle I have bubbles coming out of the radiator like crazy. I know there is not that much air in the system. According to my temperatures the car has never overheated so I don't think my head is warped. (was at the machine shop 300ish miles ago) My coolant temps are around 180-200 at idle according to our temp gun and my gauges.

What you have is not normal. I can run my car fine with the cap off at idle. I can even rev it a little and the water will climb the neck and maybe overflow the radiator a bit, but nothing "shoots" out. You have exhaust gases coming from somewhere.

[Keith Novak]

That's one problem you'll want to fix. It could have meant the head gasket wasn't lined up right and was damaged during assembly causing stuff wanting to flow where it's not supposed to go. I'd be tempted to put a dowel in, install a head gasket making sure it's on the right direction and see if it still has the issue before going further. A couple hours max.

The pictures are too blurry to see much but my machinist pointed out a head gasket leak I didn't know about due to evidence of carbon sneaking between holes it shouldn't. It looked like a little crooked brown line. Also look for scratches on the head around the dowels from not getting it lined up right on assembly. To not do that again I stick the tube and pointy tip of a Bic pen down the holes with the tip pointed up (no guts in the pen) as a guide to make sure I'm going to lower the head down straight onto the guides. The pen is long enough you can retrieve it easily once you get the head on.

[Justin Fowler]

Well it has gone 300miles since I have had any problems.

I will get myself a dowel, my head is being picked up and returned tomorrow and hopefully I can get myself a new head gasket tomorrow evening aswell and start my reinstall. If the problem continues then I figure I had a small crack that wasn't noticed in either the block or head. I am hoping it is just the gasket.

[DES4]

Make sure your machinist was thorough when the head was checked. Having had a problem, and not being certain of the nature of the issue, you don't want to dismiss possible defects in the head (warping or cracks that might only show up with magnaflux) when you put everything back together. Overlooking a problem while everything's apart can lead to much tail-chasing should the concern resurface on fireup.

The dowel pin issue could easily be the problem here (that was a good eye that caught that!), but it'd be reassuring to see physical signs of a failure before screwing it all back together. Look very closely at the headgasket; leaks caused by gasket failure can leave very faint evidence that requires a close scan to catch. Look at the mating surfaces as well.

[tony senese]

I agree the locating pin for the head needs to be replaced, but make sure the head is not warped, no matter what you do, a warped head will always eventually leak combustion gas to the water. and if it is resurfaced incorrectly, it will not get better. Constant bubbles from the radiator is definitely combustion gas leaking into a water channel in the block. You can spend lots of money on new gaskets trying to fix this. Before reassembly, make sure the head is flat.

[Dave Lewis]

The missing dowel may be in the head, flush with the surface. Don't ask me how I know. Using something like retaining ring pliers will get it out.

[Justin Fowler]

Head was magnafluxed and checked for problems today. Everything turned out alright besides 1 valve guide that was a tad loose. The head is flat with no warp to it.

I got a new dowel from my machinist who has another 1.8 laying around, I get my Fel-Pro head gasket tomorrow and I will try my luck again after I clean up the block tonight.

[Jim Boemler]

Magnafluxed? Guess you must have one of the new-fangled steel heads.

[Keith Novak]

I wondered that myself when my machinist asked whether I wanted my head Magnafluxed. Magnaflux makes a penetrant dye inspection kit in addition to the true magnetic inspection method.

[dstevens]

Magnaflux is now used as a generic term for NDT by some. They've made Zyglo and Spotcheck for a while now. Both will work with either ferrous or non ferrous material. Spotcheck is less expensive and works quite well.

[Jim Boemler]

Ah, thanks guys.

[Justin Fowler]

Got everything back together tonight. I have been waiting on parts then my injectors started leaking once I got ready so stopped for another night.

What is an average idle water temperature? My car seems to idle 200-210F, once it hits 210 my fan kicks on and cools it back down to 200 for about 5mins or so. Coolant seems to be flowing well, at 210 you can tell it is starting to boil once my fan kicks on so I figure this is normal.
What can I do for better cooling? This is my daily driven miata, so spec rules don't apply to this car! You guys have any ideas?

[Keith Novak]

Pure water boils at 212. Even in Texas. If you're running antifreeze on the street that raises the boiling point but reduces the ability of the water to transfer heat out of the engine. If you have a radiator cap on, the pressure also raises the boiling point.

Replace the stock radiator for a bigger aluminum one. That's the heat exchanger. I don't pay too much attention to where my car idles although it does start getting to 200 sitting on grid and about 210 waiting for the scales before the fan kicks on. I'm more concerned about how it does when I'm WOT and air is moving through the radiator.

While moving, the underskirt helps keep air going through the radiator instead of around it, as does the plastic piece the covers the gap at the top in front. We saw big differences in temp when we had a test day without those on a hot day in the desert so they are really important. Other than that, there's not much you can do other than make the fuel/air mixture richer to lower the temps or drive around with the heater on.

[Justin Fowler]

Pure water boils at 212. Even in Texas. If you're running antifreeze on the street that raises the boiling point but reduces the ability of the water to transfer heat out of the engine. If you have a radiator cap on, the pressure also raises the boiling point.

Replace the stock radiator for a bigger aluminum one. That's the heat exchanger. I don't pay too much attention to where my car idles although it does start getting to 200 sitting on grid and about 210 waiting for the scales before the fan kicks on. I'm more concerned about how it does when I'm WOT and air is moving through the radiator.

While moving, the underskirt helps keep air going through the radiator instead of around it, as does the plastic piece the covers the gap at the top in front. We saw big differences in temp when we had a test day without those on a hot day in the desert so they are really important. Other than that, there's not much you can do other than make the fuel/air mixture richer to lower the temps or drive around with the heater on.

I have a 52mm Aluminum radiator, and I run a 90/10 water/coolant ratio.

I am yet to build me a underskirt, I started on the top cooling panel today and I plan to get the bottom going soon. At idle I am only concerned because I have 2 gauges that will read 200F and 2 that read 250+. According to the temp gun we have it shows 190-200F and I know I am not overheating, maybe I just have crap gauges.