Well....

This forum has been a tremendous help in getting my newly acquired 87 300SDL up from a "reliable starter with no power" to a "downright fun to drive Big Benz." Over the course of the past month, I have cleaned up the vacuum system, done the diesel purge, changed filters, etc. This has brought the car from about 60hp up to pretty close the factory spec (no dyno, but it drives happily at 90mph) Unfortunately the sudden transition for this old gentleman from bed-ridden shuffler to octogenarian marathon runner has caused him to break a hip-bone....

I really had hoped that my first post to the forum was going to something more fun than this....pretty significant coolant leak has developed suddenly and I suspect it's either a cracked head or blown head gasket. Would be delighted if you guys told me it was in fact a cheap and easy fix like a loose freeze plug.....but I doubt it.

The leak is a "drip-pause-drip-pause-drip-pause" kinda deal and it happens whether the car is running or not (pretty sure it's fast when running). The point of origin is the back of the engine right at the very back of the exhaust manifold. The drip falls off the end of the exhaust manifold and I can't see it's true origin because the heat shield is in the way.

Where am I at, gentlemen? I was prepared when I got the car for a potential $$$$ fix, but hoping it's more a $$$ fix.

/Alex
digital diesel
87 300SDL 171K - "The Velvet Hammer"

You can try a block sealant, but that's only a bandaid. and probably won't work either. Get a small mirror and find where the leak is coming from. Oh, and welcome to the forum.

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Closing the store
Benzbonz.biz on your smart phone or tablet.

Well you can pressure test the cooling system and/or have the oil sent out for an analysis to see if coolant is in the oil.

At least that is where I would start.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Now why didn't I think of that,,, yes pressure test the system. you will easily see where the lead originated.

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Closing the store
Benzbonz.biz on your smart phone or tablet.

I could use a little step-by-step here...

I'm a pretty competent mechanic when it comes to suspension, electric, vacuum systems, and brakes, but I'm a little thin on gasket/fluid stuff.

Do I need a specialized radiator pressure testing device(s)? What precisely would I be looking for during testing

Additionally,

After reading through some coolant posts:

-my temps were reading consistently low before the coolant leak. I'd say they were reading around 50-60C instead of the standard 80C. I realize the coolant temp sensor could be faulty, but every time I was under the hood after/during running, I thought it seemed "cool"
-the leak drips out all the time, but goes out much quicker when running

Is there some condition which would cause low operating temps and then blow out the head gasket or crack the head?

I'm planning for the (seemingly likely) cracked head. This car will be my daily driver so my plan would be:
-Rebuilt Metric Motors head (other suggestions welcome)
-New head gaskets (original gasket must be measured, correct? multiple versions as far as I've read)
-New radiator, fan clutch, thermostat, temp senor, hoses...maybe water pump? anything else (think daily driver)
-Citrus flush on block and core
-Probably do nozzles and fuel seals, and vacuum pump, but that's not really a separate topic.

And yes, I have FSM.

Timing chain with tensioner and updated timing cover come to mind. Reseal the IP as I am sure yours leaks, most do.

May be (will be) easier to just pull the motor and rebuild it on a stand. As you will want to replace the oil pan gasket if the timing cover comes off and I would inspect the rear main closely.

You will want to replace the head with an updated version if your early head is indeed cracked and it is smart to do anyway. Plus I do not believe MM would even rebuild the early version.

Looking at $3500-5k to do it for all parts probably. Just depends how you shop.

I would at the very least reseal the trans also, if you are pulling the motor (also MUCH easier to pull trans with the motor). Depending on mileage (150+), I would even consider having it gone through. Pricing varies from $1k-2500. Should be on the low end as you will not be charged with the labor to remove and reinstall plus there is no need for a new torque converter as there is no lockup clutch to wear. Inspect flex discs while in there.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Charactaristically the cracked heads are in the combustion chamber between the valve seats on your type engine. There is little likelyhood of you having a cracked head causing this leak. Clean the area well and have a look with a mirror or something before doing anything more.

It is hopefully something like a head gasket. I do not know where the rear block frost plug is on these engines. It may be a small possibility as well. It might be too low to be the issue though.

Thanks for the info, guys....

There's 6-inches of snow on the ground now...and rowhouse living does not include a heated garage. (I was actually on the the street on a creeper when the snow started to fall) I'll get out the degreaser and "mirror on a stick" when the air temp gets above freezing. The challenge is that the exhaust heat shield is directly in the way... trap ox replacement pipe needs to come off to get behind this shield, right?

Any chance head bolts have "loosened up" causing a leak?
Any ideas on the low-temp reading?

1. Nope. Even if they did, you would still have to yank the head to replace gasket.

2. Bad thermostat. Bad gauge. Bad wiring. Bad sender.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

I know how you feel, Dig. Exactly. My 14 head isn't cracked, though, so you don't, necessarily, have to jump to the conclusion that yours is a goner.

You might get lucky and find that the leak is coming from the block heater, as it is right there. When the cylinder heads on these fail, it is my understanding that the coolant comes out the tailpipe. Any oil on top of the coolant in the overflow tank?

A lot of these guys are real quick to spend your money. That's an easy trap to fall into. I don't expect my '87 to last forever. It has a pile of miles on it, and I just need a year or two out of the car until I can find a Sprinter or a NICE 124 wagon. I rolled the dice and just replaced the head gasket. Period. No trip to the machine shop, just off - hit it with the roloc on a die grinder, clean w/acetone a couple times - and right back on. The car seems fine. Wish it started a little easier, but I'll get to that.

Long story short, don't lose any sleep. Just figure out what's wrong and fix it.

Need anything, lemme' know.

Jay.

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On the road, currently:
'83 300D (German spec.) 168k mi. - - Wolfgang (tucked snugly away for the winter!)
'87 300D 375k mi. - finally went over to "The Dark Side"
'87 300TD 225k mi.
Cannondale 66cm CAAD5 w/Campy/Jamis Aurora
Hujsak Custom Fixie/Landshark Track Shark Custom/Ahearne Custom 29'er

1. Labor is labor and parts is parts. I do my own work and enjoy spinning a wrench....so $150 worth of gaskets and two days of time with a torque wrench and the FSM is just fine and dandy....a $1200 head rebuild is a bit to choke down, but will take it if I have to.

2. Since the car has been slow to come up to temp and noticeably cool under-hood, I think it's probably a bad thermostat - open early or all the time. Since I've had to top off with green stuff (better than no coolant or pure water), The Hammer needs a coolant flush anyways. Went ahead and bought a new expansion tank and cap too. The old tank was so yellowed, it was unreadable for level....had to choke a bit on the price $160 for a tank (most prices were $200+), but...seeking daily driver status.

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I realize it's sacrilegious to a purist, but what would the "permanent" consequences of using head gasket repair compound be? I mean, if the silicate plugging goop gets me 6-12 months of time to plan my finances to track down a 606 head, are there any potential damages to the lowers of the engine?

No, I am being realistic. These vehicles all suffer from the typical failures. Makes no sense to skip out for a some money if the part fails later you will be SOL and back doing it again. From what I gather he does not need this vehicle simply to run for a few years then is going to trade up

Why would you not replace the chain/tensioner if stretched? Why would you want your IP to still leak oil on your engine mount eventually eating it away? Do you want to pull the head again later to save $120 over the cost of the updated timing cover? Why would you not replace the injector nozzles while apart?

Same goes with a leaking transmission, they almost always leak from the front pump/stator support area. Fix it while the motor is out.

If his head is indeed cracked, then he is really up creek without a paddle. Installing a used No 14 head just is not a good idea as you have no clue how it was treated in the past.

He is prepared to spend some money and to be reliable you will have to do this.



No real sense in just pulling the head and swapping a gasket without pressure testing the head along with at the very least swapping stem seals with valve springs.

Last person I know used that stuff ended up with a plugged radiator. YMMV.

No idea what the 606 head swap would entail, never looked into it.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

I think Metric motor does a rebuild on this head for about $700. That's just an example.

On the cheaper side, I'd take the head into a shop and get it tested, grind the valve/seats, replace the valve stem seals. They can tell you if any of the valve/springs need replacing. They very seldom do, even the valve guides wear extremely well.

Unless you recently had the chain replaced, I'd replace that as well.

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)