Intermix - long post, asking for advice on repair - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Doug427 · 10-07-2018, 02:50 PM

I have a 2002 Boxster S. Long story short it has intermix. No water in the oil, but oil in the water. Engine runs well, and VERY strong. I changed the oil cooler, and it didn't change anything. I can only assume it's a cylinder head. Is there anything else it can be within reason? I know I can take it to a shop with Porsche experience, but with what I would have to pay them to diagnose I can pay for half the repair. I have two choices - both involve dropping the engine, which I can do.

First, I can use the existing engine, since it runs so darned well. Remove the heads, send them to the place I read about in Costa Mesa or elsewhere, have them welded up and rebuilt, and reinstall. How hard is it to R&R heads on these engines? I have rebuilt many American and Japanese engines, so I know a bit, but I've never done one of these Porsche engines. Not going to rebuild, just pull the heads and reinstall. Of course while it's out I'll replace clutch, IMS bearing, rear seal, plugs and tubes, IOS, engine and trans mounts, etc. Also, the engine I have now has a chain rattle on startup, which quickly goes away. Not sure what the repair is for that, but if reasonably easy, I'll do that while the engine is out as well. Does anyone know of a link to a good how to on this job? Any ideas on costs for the work on the heads? Any and all info on this job would be greatly appreciated.

Second choice is to get a second hand engine. A new/rebuilt is out of the question for cost reasons. Problem with this, of course, is not knowing what's wrong with the engine I would be buying and installing. I may be trading a known problem for a new, unknown problem.

As best I can tell, a used engine will be between $3K and $4500K. For that price I think I can do a complete top end repair and rebuild on mine, fixing all the suspect parts, chain rattle, IMS, etc. In the end the original engine will still be in the car, and I know the engine is a known quantity. My hesitation is twofold:

-Is it in fact the heads? What else can it possibly be?
-How hard is it to remove and replace the heads, keeping everything in time?

I'm eager to hear what you guys think on this. Your input is greatly appreciated. Hopefully with a little back and forth my options will become clearer. Thanks.

Gilles · 10-07-2018, 04:17 PM

Sorry about your intermix issue, perhaps you may want to pressure test the cooling system before any dissasembly.

Also would recommend Hoffman Engineering shop to rebuild/repair your heads as they do have many years of experience with the M96/97 engines.

Good luck!

thstone · 10-07-2018, 07:53 PM

Quote:

Originally Posted by Gilles

... pressure test the cooling system before any dissasembly.

^^ This. ^^

Bite the bullet and spend $150-$300 to have the cooling system pressure tested. Then you will know exactly where the problem is - you'd hate to pull the engine, tear down the top end, and find the heads to be fine.

I'm not saying that its not the heads; I'm just saying that the more you know before you start tearing down things, the better.

Oggie · 10-08-2018, 04:17 AM

Please excuse my ignorance, how will pressure testing locate the issue (genuine question)? I understand that you can pressure test the cooling system and if there is a leak the pressure will slowly go down. How would I locate where the leak is? Do I just assume that if, under pressure, no coolant is visible on the ground, it must be into the cylinders, thus it is the head?

I also know of

chemical testers that can test the coolant for CO2 which can show if you have combustion gases seeping into the cooling system. Wouldn't this be a more useful test in this instance?

Asking this, as I am having a similar issue to the OP, but haven't yet replaced the Oil Cooler.

seningen · 10-08-2018, 05:52 AM

You might check the oil cooler on the top of the engine for leaks -- either in the oil cooler or in the o-rings.

___ SORRY READ CLOSER ____ you already changed this to no avail...

Since you are getting oil into your coolant and not the other way around -- that's not as severe.
On my old S Coolant in the oil prompted me to do a complete rebuild 10 years ago. (failed WP lead to a freeze plug failure in the head).

I think there is also a path for the oil to enter coolant via the AOS - but I'm not 100% sure there.

Otherwise its either cracked cylinder head or cracked cylinder liner.

mike

thstone · 10-08-2018, 06:28 AM

Quote:

Originally Posted by Oggie

Please excuse my ignorance, how will pressure testing locate the issue (genuine question)?

A good shop should be able to determine not only if the cooling system is leaking but where it is most likely leaking from.

For example, they can pressurize the cooling system and monitor cylinder pressure at the same time - if the cyl pressure shows an increase, then the head is likely cracked in that cylinder. This isn't an exact test (in psi), its just an indicator of what might be going on inside the engine.

In your case (where you haven't yet replaced the oil cooler), they can easily figure out if that is the source of the leak (they will hear the pressurized air coming out of the top of the engine where the oil cooler mounts).

A good shop knows all of these kinds of troubleshooting techniques and has the experience and equipment to perform them since that is what they do for a living - and that is why they are worth $150/hour.

Now, it is definitely possible that they can't find the leak (and you might feel as if you wasted your money) but as I said, its worth a couple hundred bucks to see what they might turn up before starting a tear down.

I had my local shop do this test on my Boxster when I was losing coolant but had no obvious leaks and no intermix - where is it going? They found that I likely had a leak into a cyl and a subsequent leak down test on the cylinders confirmed it (coolant was leaking into a cylinder and going out the exhaust).

j.fro · 10-08-2018, 06:39 AM

In February I went through this.
Before you pull the engine, rig up a garden hose to the coolant system and back flush the hell out of it to get all of the oil/coolant and pieces of the water pump impeller out.
Set the engine to TDC and put the pin in so it doesn't move. If it's not at TDC when you go to pull the cams, the valve tension may break a cam.
Get the heads off and have a look at the cylinders to determine that there's no cylinder scoring. If you've got scoring, there's no sense fixing the heads. If the cylinders are good, with rebuilt heads you'll have a better engine with no mysteries.
It cost me $2500 from Hoffman Machine in GA to check my heads, repair the crack, repair a couple of broken exhaust studs, do a mild porting job, regrind the valves, and replace the valve springs. ARP head studs were $500; the full gasket kit was another $500 (both from eBay dealers).
That chain rattle you've got is from wear on the vario-cam tensioner pads and plastic chain timing ramps. Replace all of that. From Pelican it will cost you about $350, I think. The tensioners themselves seem pretty indestructible and should be good.
There are a ton of other "while you are in there" items that will run the bill up but are worth doing: AOS, rebuild fuel injectors, rebuild/replace lifters, coils, plugs, plug tubes (the gasket kit has all of the o-rings, etc), water pump, any sensors that seem shot, etc.
I did almost all of the work, but had a knowledgeable buddy set the cam timing. All in, I think I spent about $5K
If you have questions or just need an empathetic shoulder to cry on, PM me. Once it's back together and running perfectly you will quickly forget what a PITA this is.

Starter986 · 10-08-2018, 09:04 AM

Quote:

Originally Posted by j.fro

In February I went through this.
Before you pull the engine, rig up a garden hose to the coolant system and back flush the hell out of it to get all of the oil/coolant and pieces of the water pump impeller out.

Can you describe how to do that? To where, and how, you connect the garden hose?

Thank you.

j.fro · 10-08-2018, 05:49 PM

I made these two tools from plumbing stuff available at Lowes. the longer one is the inlet, with a valve to control flow.
Get the car in the air and remove the underpanels. Disconnect the rubber coolant hoses on the driver side where they go into the center tunnel. You'll need another short rubber hose to connect to the metal pipe. Start by pushing water towards the radiators. Once the water runs clear, flip the hoses and push water towards the engine. You're going to run a lot of water, but water's cheap. Oil in the system will destroy the rubber hoses. Of course, if you don't get all the little pieces of plastic impeller out, they are sure to jam up in the heads and cause another hot spot.

Oggie · 10-09-2018, 02:49 AM

Quote:

Originally Posted by thstone

A good shop should be able to determine not only if the cooling system is leaking but where it is most likely leaking from.

For example, they can pressurize the cooling system and monitor cylinder pressure at the same time - if the cyl pressure shows an increase, then the head is likely cracked in that cylinder. This isn't an exact test (in psi), its just an indicator of what might be going on inside the engine.

In your case (where you haven't yet replaced the oil cooler), they can easily figure out if that is the source of the leak (they will hear the pressurized air coming out of the top of the engine where the oil cooler mounts).

A good shop knows all of these kinds of troubleshooting techniques and has the experience and equipment to perform them since that is what they do for a living - and that is why they are worth $150/hour.

Now, it is definitely possible that they can't find the leak (and you might feel as if you wasted your money) but as I said, its worth a couple hundred bucks to see what they might turn up before starting a tear down.

I had my local shop do this test on my Boxster when I was losing coolant but had no obvious leaks and no intermix - where is it going? They found that I likely had a leak into a cyl and a subsequent leak down test on the cylinders confirmed it (coolant was leaking into a cylinder and going out the exhaust).

Being a DIY sort of guy, it so happens that I just picked up a cooling system pressure tester off eBay (for 99 cents!), so I will give it a try. I hope to hear it leaking at the oil cooler. This is a much easier fix.

I've pulled each of the plugs and it all looks good in that department, they are all a consistent colour - I'm hoping this means that there aren't any leaks into any of the combustion chambers. I have my fingers crossed!

Starter986 · 10-09-2018, 05:14 AM

Quote:

Originally Posted by j.fro

I made these two tools from plumbing stuff available at Lowes. the longer one is the inlet, with a valve to control flow.
Get the car in the air and remove the underpanels. Disconnect the rubber coolant hoses on the driver side where they go into the center tunnel. You'll need another short rubber hose to connect to the metal pipe. Start by pushing water towards the radiators. Once the water runs clear, flip the hoses and push water towards the engine. You're going to run a lot of water, but water's cheap. Oil in the system will destroy the rubber hoses. Of course, if you don't get all the little pieces of plastic impeller out, they are sure to jam up in the heads and cause another hot spot.

Thanks!

What diameter size is that larger/longer pipe? I assume you push that into the hose, snuggling it in, and then turn on that water...?

Thank you.

j.fro · 10-09-2018, 09:15 AM

It's 2" or so. Fits snugly in the factory coolant hose, but I'll put a screw clamp on it to make it secure. Same for the drain hose.

Starter986 · 10-09-2018, 11:05 AM

Quote:

Originally Posted by j.fro

It's 2" or so. Fits snugly in the factory coolant hose, but I'll put a screw clamp on it to make it secure. Same for the drain hose.

Thank you! Awesome.

One more question...

No concern about running tap water through everything?

j.fro · 10-09-2018, 04:11 PM

Tap water... Good question. No worries at all. When the engine is back together, fill with distilled water and run it a up to temp. Drain that and then fill with your coolant mix of choice. When the engine is apart, use compressed air to blow out the coolant passages in the block. The heads will by dry and clean.

Starter986 · 10-10-2018, 06:37 AM

Quote:

Originally Posted by j.fro

Tap water... Good question. No worries at all. When the engine is back together, fill with distilled water and run it a up to temp. Drain that and then fill with your coolant mix of choice. When the engine is apart, use compressed air to blow out the coolant passages in the block. The heads will by dry and clean.

Thank you!

tonythetiger · 10-10-2018, 08:15 AM

you never mentioned the mileage on this engine, but if you have chain rattle, I will assume you are approaching 100K. IMHO, and Hoffman might agree, simply fixing the cracked head and having the heads rebuilt still leaves you with an engine prone to failure. Hoffman discouraged me from just fixing the heads.
i wrestled with the decision on my 2000 S with intermix and just replaced the car. Painful but I ended up with a better car and never looked back. I got a little money out of the old one as well.
I think once I started driving my first 986S, i wasn't going to give it up.

Doug427 · 10-10-2018, 01:41 PM

Quote:

Originally Posted by tonythetiger

you never mentioned the mileage on this engine, but if you have chain rattle, I will assume you are approaching 100K. IMHO, and Hoffman might agree, simply fixing the cracked head and having the heads rebuilt still leaves you with an engine prone to failure. Hoffman discouraged me from just fixing the heads.
i wrestled with the decision on my 2000 S with intermix and just replaced the car. Painful but I ended up with a better car and never looked back. I got a little money out of the old one as well.
I think once I started driving my first 986S, i wasn't going to give it up.

Replacing the car is always an option, and I have thought of that as well. Problem is it's just not worth much at all with intermix. Car has 106K miles on it, it's only worth about +/- $8K with a good engine. With a bad one, it's likely not even half. I hate to just pack it in and throw away all the $ I have spent on it so far. It's not just the money, either - I feel like I've given up if I do that and I hate to do that. I bought this car very cheaply, but have put lots of money and work into it to get it where it is now. Tough to just pack it in at this point. I may end up doing that, but I really don't want to.