discman017

Hi all! I've had a 2006 RL for two years now and absolutely love it. But recently, it has started shooting coolant out the plastic reservoir. I've taken it in for service, and the tech seems as stumped as I am.

Background: I live at 6700 feet elevation along the Front Range in Colorado. Most of my driving is in town, about a mile high. But to get home, I have to drive up about 1300 feet elevation over the course of 3 miles. When I park in my driveway, coolant is bubbling and shooting out the reservoir, leaving a puddle in my driveway. It doesn't seem to do this when I'm driving on flat land in town, only after I've driven up to my house.

The tech tested the system to make sure it's holding pressure, and it checked out OK. The fans are working OK. He replaced the radiator cap, in case that was leaking, and it still boiled over. He then replaced the thermostats (apparently the RL has two different coolant thermostats), and it still boiled over. The repair shop is in the flat lands, so the tech has only gotten the engine temp up to 214, and he hasn't been able to see it boil over. But as soon as I drive the car home, it boils over again.

Today I hooked up a Bluetooth OBD reader with a smartphone app and watched the engine coolant temp as I drove home. Driving in stop-and-go traffic in town, it never went above 204. Driving up to my house, it got as high as 221 and then ranged between 212 and 221.

My understanding is that a temp of 221 shouldn't boil coolant. Water boils at 212, but antifreeze boils at a higher temperature. And the cooling system is under pressure, which increases the boiling point by about 45 degrees. So a 50/50 water / antifreeze mix shouldn't boil until maybe 270 or higher, and my scanner is reading no more than 221. It shouldn't be boiling. But it is.

If you want to see for yourself, here's a video that I took today of the coolant boiling out the reservoir: https://drive.google.com/file/d/1KkV...z3lm6vRmL/view

Why would the temperature read OK, with a new thermostat, but the coolant still boil over? Only thing I can think of is the system isn't maintaining pressure, so the boiling point is lower than it should be, but the tech already checked the pressure.

Is there a higher-boiling-point fluid that I can use in place of the typical 50/50 antifreeze/water mix? I mean, the engine temp seems fine, so the cooling system is doing its job. My problem is I lose half my coolant and make a mess of my driveway and under my hood every time I drive up the hill to get home. So maybe a different fluid would be more resistant to boiling?

Any ideas would be so much appreciated. I'm totally stumped, and my repair shop is too. Thanks in advance for any help!

altair47

If the thermostat opens properly, the engine temperature is normal, you have antifreeze, not water, then by all indications it is the cylinder head gasket. Have you done an Combustion Leak Test?

discman017

Thanks for the quick reply! Yes, all of those conditions seem to be true. Head gasket, ugh.

The mechanic hasn't been able to reproduce the problem at temperatures up to 214. They also pressure tested the cooling system and didn't find a leak.

So is it a head gasket leak that only manifests at temperatures higher than that (up to 221, as I measured yesterday)? Thermal expansion exposes a small leak in the gasket that seals back up at lower temperatures?

If so, then combustion gases get forced into the coolant, causing the bubbling sound that I'm hearing (which then isn't boiling, like I thought). Then the increased pressure in the cooling system gets relieved through the expansion tank. Is that what's likely happening?

And if that's the case, then I guess the mechanic can't perform the leak test, since he hasn't been able to reproduce the leak. I'd have to do the leak test when the coolant is actually bubbling.

Final question: I see DIY head gasket sealer products that get mixed in the coolant (for example, ) and others that get mixed in the oil ( ). Definitely seems like I want to give one of these a shot before spending $2000 to take apart the engine. Is one of these products better for the type of leak I have? And if I'm understanding the behavior of the leak correctly, I assume I need to get the temp up to 220 or so to make sure the leak is exposed so it can be sealed?

Thanks again for your reply, and I would really appreciate confirmation that I'm thinking about this correctly, or correction of whatever I'm misunderstanding. Thank you!!

vindroid

Hi, what was the outcome of this?

altair47

You need to do a test on a hot engine to be sure the gasket is the problem. Mischel's book gives 7 hours for one head, 11 hours for both. Replacing head gaskets is a very simple job on J35 engines. Any liquid to solve this problem is only a temporary solution, but there is a good chance that it will make things worse. If you want to sell the car, you can take the risk and fill it up, if you want to continue using the car, then change the gaskets.

discman017

Today the mechanic gave me a call confirming that the car needs a head gasket replacement. They quoted me $4100! So it doesn't sound like it's a simple job for them. Are you sure that it's just 7 or 11 hours work? Should I be looking for some sort of specialist who just does engine rebuilds rather than a general auto repair shop?

And when you say liquid could make things worse: What additional problems could it cause? Seems to me that if I really need a $4100 repair, then the car is basically totaled, so I might as well give it a shot.

discman017

Head gasket replacement needed. Bummer.

altair47

Grinding the cylinder head is required only if the engine has been overheated, in your case, most likely, you just need to remove the heads, clean the surface, put in two new gaskets with new cylinder head bolts and that's it. This work is very simple because the J35 engines use a timing belt, not a chain. Drain the antifreeze, remove the intake manifold, remove the valve covers, remove the pipes with the fuel rails, unscrew the exhaust manifolds along with the studs, remove the timing mechanism, unscrew the head bolts and remove the heads. This is a super easy job. Speaking about the simplicity of this engine, here is a video where a guy takes out a piston in less than an hour, and in order to get it, you need to remove the oil pan into the pan, but in your case, you don’t need to remove the oil pan. Mitchell gives 11 hours for this job because he includes valve adjustment. Without adjusting the valves, the work is done faster.

discman017

Thanks for all the advice. You've convinced me. I'm going to try to do it myself, so I started a new thread specific to this job (head gasket replacement) rather than diagnosing the symptom (coolant shooting out of reservoir). I'd appreciate any help you can offer along the way! Thanks again!