Overheated M42: the depressing saga

[nomad]

So I'd been lazy and put off installing my new water pump and thermostat I have in the garage. I guess my car got pissed and decided to punish me.

On surface streets with A/C on I suddenly noticed the check engine light come on and the temp was pegged red. :eek: I cranked the heat up and no heat came out. I pulled over just as I rolled down the freeway on-ramp and sat on the shoulder. I looked at the rad and it was low on water in the expansion tank. So I'm thinking water pump or thermostat or leak. :confused:

I had just added a bit of water to it this weekend just to be sure the fluids were topped off. The car cooled down to middle temp level and the car never made any sounds or put out any white smoke and didn't have a smell of antifreeze.

The Freeway tow truck topped off the rad with water and the expansion tank filled, then the water was sucked into the engine and the level was about 1/4 full on the tank. I cranked it up, put the heat on high and drove home at 50mph. The heat didn;t come on right away, it took about 40 seconds. The temp guage read to the 3/4 mark on the way home but held steady till I was on surface streets, then it crept up.

When I shut the hot car off at home I saw that the expansion tank had water full all the way to the cap. I let it sit and cool and now the water level is under the middle mark again.

So here's what I'm thinking:
1. The water pump works (I'll replace it anyways) because it is pressurizing the system.
2. The heater core works as evidenced by the heat and temp reduction but could be clogged or could have issue with the valve to the heater core?
3. Thermostat could be toast and failed half closed or full closed. The hoses were hot but the rad wasn't overly hot when it pegged red. Thermostat could be restricting all flow, hence the expansion tank totally filling with water.
4. I didn't see any water in oil or oil in water so I'm hoping I missed the bullet and the HG is ok.

I'm going to buy a whole hose set, change water pump, thermostat (check for bypass hole, drill if needed), belts, flush, fill, bleed. Any suggestions? Insights?

Do you use any permatex on the thermostat housing gasket?

[nickmpower]

you head is probably cracked, take the rad cap off, start the car, and look for bubbles in the tank

[nomad]

Something this serious would be evidenced by water in the oil and/or oil in the water though. I'll have to look for that as they seem fine so far.

[nickmpower]

not nessesarily, the head cracks inbtween the cylinder 2 exhaust seat and a water jacket.

[nomad]

What are the symptoms?

White smoke out exhaust, dripping water, slowly losing fluid, quickly losing fluid?

So you say I should just look for bubbles in a full radiator overflow tank once I start it up cold? Small bubbles, large bubbles, steady stream or occasional only?

[nomad]

So I degreased the engine tonight so I could see everything clearly and I found the leak.
I ran the engine and I saw water bubbling out of a hose connection under the intake.

I looked in the Bentley and they had a photo of exactly where it is leaking. I really hope this is the only place! You can see to the left is the oil filter and on top in the intake mani.

So I'm going to see if I can get these hoses and the coolant pipe that they are connected to.

Anyone have suggestions on changing these hoses? Remove intake mani? Replace whole coolant pipe?

[christophbmw]

So I degreased the engine tonight so I could see everything clearly and I found the leak.
I ran the engine and I saw water bubbling out of a hose connection under the intake.

I looked in the Bentley and they had a photo of exactly where it is leaking. I really hope this is the only place! You can see to the left is the oil filter and on top in the intake mani.

So I'm going to see if I can get these hoses and the coolant pipe that they are connected to.

Anyone have suggestions on changing these hoses? Remove intake mani? Replace whole coolant pipe?

replace the whole coolant pipe & the o-ring.....along with all th hoses that attach to it and you should be fine.

[nickmpower]

did you check for bubbles in the coolant tank yet?

[nomad]

Well, I just spent the last 9 hours changing water pump, thermostat, belts,  took the intake manifold apart and did the throttle body coolant bypass, replaced the water pipe and the hoses as well. I put it all back together but it's too late to fill and check it now.

I took my time, had the music going, had some beer. It took a while but I don't have to rush it and do a quick fix so I didn't. I cleaned as I worked and overall got acquainted with the M42. I don't like that little black box full of wires under the intake manifold, and didn't like the routing of coolant and vaccuum hoses in general. If I have to do it again I'll do a more thorough cleaning job with lots of carb spray in the intake.

I'll check for bubbles and see if I did any major damage to the head with this incident. The water pipe was disintegrating from the inside out. The pipe nipple broke clean off, that's why I lost all my fluid, and when I pulled the pipe out half of it stayed in the block.

Everyone should plan on replacing it if you have not already. This car has 156K on it and I see, unfortunately, a lot of little things that are original.

I plan to take the upper intake manifold off and clean/paint it with the valve cover when I do my valve cover gasket, hopefully Monday. I should also have the large radiator hoses and a new expansion tank cap by then from RMEuropean.

[RED IS 91]

Keep us posted

[nomad]

8:30AM - So far so good. No bubbles as far as I can tell, and the temp guage has stayed one tick below 12-oclock pretty firm. I'll find out how well it does today on the way home with the A/C on at 104 degrees.

1:00PM - Seemed to cool well and temp climbed till needle was nearly past 12 oclock then fell to previous reading once thermostat opened. 101 degrees right now. I turned on the A/C and the temp climbed to a needle past 12 oclock. Not happy wih that. I also saw coolant from what looked to be the heater hose connection tot he block. Damn. I knew I should have changed that hose. Looks Like I may be redoing that later this week. No steady bubbles in teh overflow tank yet but the water looks dirty, I flushed it as best I could but I think another flush will be good.

Hope nothing blows on the way home.

[nomad]

Well, I should have stayed home.

This just went from what seemed bad to worse.
First, the easy stuff. I sprayed carb cleaner on the ICV and it seemed to smooth out the idle a bit.

Then, I pulled out of work and within one block the car overheated. No hoses busted etc, but temp kept climbing to red.

Heater felt weak so maybe that is clogged?
It spewed coolant whe i relesed the pressure cap on the overflow tank. The system seems to have a lot of pressure in it.

I'm not sure if the thermostat didn't open or what.

What really gets me is that I think I do have a cracked head now. The coolant isn't chocolate milk but I did see light brown oil in the plug holes.
I guess my only choice now is to take it to a local mechanic and get the bad news.

I've got a couple grand in performance upgrades in the garage and several more buying the car and the engine is toast. No I'm looking at finding a new head or a new engine.

[tjts1]

When you can't get any heat out of the vents with the engine overheating, chances are your water pump is no longer turning. Thats really strange considering you just replaced it. Sorry to hear the bad news.

Does the electric fan turn on with the AC? What about the the clutch fan? Is it moving a lot of air when the radiator is hot? Any way you slice it, the cooling system on this engine is beyond stupid.

[nomad]

It was working this morning, everything was nice.

The clutch fan seems to work ok, once I got moving (and rpm went up) the temp steadily rose to red.

A/C fan has worked fine.

I felt the radiator and it was not too hot whereas both hoses were really hot.

I had flushed out the rad when I did the overhaul and it flowed well. Maybe it is just a really really bad clog that comes and goes.

The thing that really scared me was the nasty light brown oil in the sparkplug holes. It wasn't there this AM because I just cleaned them out of black oil that I discovered.

Maybe I can drive as far as it'll let me go before getting too hot. I really would rather do the work myself but time is precious.

I need to find a 318ti head or something.

[D. Clay]

The oil in the spark plug holes is from the valve cover gasket. There are small gaskets around the plug openings. It's good that it's just oil
 - indicating it's just leaking a bit. You could tighten the bolt in the center of the valve cover. Don't get too tight as they are known for stripping. May be a stupid question, but are you bleeding the cooling system using the plug on top of the radiator tank. in the realoem drawing of the radiator. It's #8.