Unknown Coolant Leak

jay07 · Jun 12, 2017

Hey guys,

I have a 07 GT with a Saleen supercharger and have been having a slow coolant leak for a while now.

I fill the reservoir to the max fill line, and then maybe a thousand miles later, it is down to the low fill line. The system was filled and checked with the engine completely cold.

I read on the forums about some people having issues with the hose clamps, but I have never had any signs of coolant on the garage floor.

The only other symptoms I can think of which may not even be related are that the serpentine belt squeaks for quite a while when I first start the car up although I have never found any coolant on the hose! And also one of my short term fuel trim values on one bank seems to jump around a lot more than the other.

Does anyone have any ideas on what I can test/check to try to track this down? I'm not sure if head gasket leaks are common on these cars or not.

Thanks for any tips!

Dino Dino Bambino · Jun 13, 2017

From the symptoms that you've described, it's most likely that you have a small head gasket leak on the cylinder bank that has the erratic short term fuel trims. Since the engine is supercharged, the most likely underlying cause is detonation.

jay07 · Jun 14, 2017

Bullitt95 said:
From the symptoms that you've described, it's most likely that you have a small head gasket leak on the cylinder bank that has the erratic short term fuel trims. Since the engine is supercharged, the most likely underlying cause is detonation.

Is there any easy way to test this before I try to get it fixed? Or any idea to determine how urgent it is?

Is this a job I can handle myself on these cars? The biggest job I have done before is a timing belt on my 94 Probe. Any recommendation for what else I should do at the same time or what brand head gasket is best? My car has 60,000 miles on it so it is not really near time to redo the timing yet.

Thanks in advance!

Dino Dino Bambino · Jun 14, 2017

Do a compression test on the four cylinders in the affected bank. It's most likely at least one of them will be low on compression and have a spark plug that appears to have been washed by coolant.
If my diagnosis is correct, you might want to find out what caused the head gasket to leak (possible lean condition or too much timing advance).

racerraj · Jun 15, 2017

Before trying too much, check for signs of leakage around the weep hole on the water of the water pump. Mine was leaking there but never showed signs of a leak when parked.

jay07 · Jun 18, 2017

racerraj said:
Before trying too much, check for signs of leakage around the weep hole on the water of the water pump. Mine was leaking there but never showed signs of a leak when parked.

I'm not even sure where that is. I have an electric water pump, where would I look for the weep hole? Just look around the general water pump area for water? Would it show up in a compression test on the coolant system?

Bullitt95 said:
Do a compression test on the four cylinders in the affected bank. It's most likely at least one of them will be low on compression and have a spark plug that appears to have been washed by coolant.
If my diagnosis is correct, you might want to find out what caused the head gasket to leak (possible lean condition or too much timing advance).

I'll try to do this when I get a chance. Unfortunately most of my weekends are tied up lately so I haven't had a chance to look into it further.

racerraj · Jun 19, 2017

Hmmm... Not even sure f electric water pumps have a weep hole. But yes, look it over good, because if it has been leaking, it will stain. Being supercharged, I'd guess a head gasket may be the problem though. Still worth just looking at the pump since that's easy to do.

jay07 · Jun 29, 2017

I finally had a chance to take the plugs out and take a look today. It doesn't look like any of them have any issues to me. Do these look normal? They grey stuff is nickel anti-seize BTW.

I also checked around the water pump and did not find any wet spots. I may try to pressurize the system and see if I can find any leaks.

Dino Dino Bambino · Jun 30, 2017

Nothing there to suggest a head gasket leak but since the plugs are out anyway, do a compression check on all cylinders to make sure they're even across the board.

jay07 · Jul 8, 2017

Bullitt95 said:
Nothing there to suggest a head gasket leak but since the plugs are out anyway, do a compression check on all cylinders to make sure they're even across the board.

I finally had a chance to do a compression test today. I had to buy an adapter . If anyone else needs one, I got it off Amazon (OTC 5607) for around $20

I'm not sure of the cylinder numbering on this car, but here are the numbers
Passenger Driver
Rear 192 187
180 185
180 188
Front 182 185

Note that I discovered later that if I attempted to start the car again after getting the first number it went higher. So the 180 and 182 numbers were achieved without trying to stop and restart again. It very regularly would first stop around 180 and then if I tried to start again would go to 185 or so.

This was on a warm engine (15 minute idle)

I did smell a little bit of coolant when I started doing the test but I was not able to figure out where it was coming from. I thought maybe the reservoir but was unable to find any actual evidence of a leak .

Real time recon · Jul 8, 2017

Those plugs look a little funky to me.I'm not a supercharge guy,but they have a lot of rust on em. View attachment 585318 View attachment 585318
These were pulled from a 10 year old 302....just saying

Dino Dino Bambino · Jul 8, 2017

jay07 said:
Passenger Driver
Rear 192 187
180 185
180 188
Front 182 185

It looks like the engine's fine 'cause the compression numbers are within 10% across the board, and that's very good news.
Therefore your engine must have an external coolant leak and since it's hard to find, you might wanna check in these two hard-to-see places:

1. The heater hose running front to back in the engine block valley under the intake manifold.
2. Water pump.

jay07 · Jul 20, 2017

Still searching for the leak. I did a cold cooling system test under pressure and the pressure holds steady, I did not have time to do a test while the system was running. The cap also tested okay.

One thing I did notice is that the oil level seems like it may be going up slowly, either that or I put a little too much oil in last time I did an oil change. I'm going to do an oil test next as I suspect the coolant may be going into the oil, but I want to verify that.

Is it common at all on our engines to get a leak between the coolant and oil? I would have thought that would show up in a compression test?

Real time recon · Jul 20, 2017

IF you have coolant in the oil its easy to spot.
> View: https://www.youtube.com/watch?v=gPQkVq4rypg

jay07 · Jul 20, 2017

Wow, that is mildly horrifying .
I can tell you that from the dipstick is looks fine, but I'll have to run the engine and check it so that it is 'mixed' if there's any there.

jay07 · Jul 20, 2017

Real time recon said:
Those plugs look a little funky to me.I'm not a supercharge guy,but they have a lot of rust on em. View attachment 585318 View attachment 585318
These were pulled from a 10 year old 302....just saying

I think they get a lot of carbon build up on that extension leading from the threads out to the cylinder, but I could be wrong.

jay07 · Jul 27, 2017

Alright, I did more hunting with tests on the cooling system and did finally find a very small radiator leak. It was never enough to drip, it just collected in the bottom of the radiator housing instead.
Frustrating for a CSF aluminum radiator with only 13,000 miles on it (out of warranty of course). Going to pull it and verify that it is the radiator and not the lower hose connection and see if I can get it fixed at a local radiator shop.

Thanks for all the help guys, learned new stuff

Real time recon · Jul 27, 2017

Hey Jay
Protect that radiator with some cheap insurance.Nomax screen.> http://www.ebay.com/itm/Speedway-Mo...r-Protector-Screen-15-x-22-Inch-/381244396685
I've had it on for 2 years and still as good as new.Caught a ton of bugs,1 bird & several stones.Nothing penetrated to radiator.
Only comes in that puke tan color.So if you want it black or a different color ,it takes 1 rattle can to cover both sides of the protector...

jay07 · Aug 10, 2017

Okay, so problem solved.

The old CSF radiator had a small leak on the bottom row. That obviously cannot be fixed.

Oil check from Blackstone Labs came back with 0% for coolant (hurray!).

I've got another radiator in the car now and was flushing the system out last night, so should be good to go tonight I hope .

So bottom line is check very carefully behind the plastic piece under the radiator and make sure you don't have a small leak there. Mine wasn't leaking much and wasn't obvious without looking closely but was enough to make me wonder where all the fluid was going.

jay07 · Aug 10, 2017

Real time recon said:
Hey Jay
Protect that radiator with some cheap insurance.Nomax screen.> http://www.ebay.com/itm/Speedway-Mo...r-Protector-Screen-15-x-22-Inch-/381244396685
I've had it on for 2 years and still as good as new.Caught a ton of bugs,1 bird & several stones.Nothing penetrated to radiator.
Only comes in that puke tan color.So if you want it black or a different color ,it takes 1 rattle can to cover both sides of the protector...

That's an interesting product, I had never seen one of those before.

Unknown Coolant Leak

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