1987 300TD head/gasket fears - PeachParts Mercedes-Benz Forum

Beanybean · #1 10-19-2012, 12:18 PM

Hey guys,
I've been digging around the different forums and searching the symptoms of my 87 300TD (recent upgrade from 1980 300td non-turbo), and I'm afraid I might have cracked my head or blown the gasket.. Let's try to alleviate or confirm my fears..

Situation:
I replaced the water pump two days ago due to leakage and a loose bearing.

Flushed and replace coolant (50/50 MB to di water). I had no trouble pouring in all two gallons (into the engine from the top rubber hose, then the rest into the reserve tank.) Didn't seem to need burping..? Cool, or so I thought. Drove to work and the car acted fine at first on the freeway -it came up to temp and hovered around 85, but when I got some more RPMs and spun up the turbo on a little incline (love that sound), it rose to 100, beyond and then all the way to 120. Pulled over as soon as I could (less than a minute right around the white-red line separation on the temp gauge..).
Checked engine: (took a while to slowly let pressure out of reserve tank without letting water gurgle out as well - afterwards the reserve tank was considerably less full -I refilled with DI h20 and noticed the following behavior:

1. The fan clutch is apparently shot. Once the car is hot it completely freewheels when I kill the engine from the hood. Not sure if it was working before or not.

2. With the reserve cap off and the engine idling (or reving, doesn't seem to matter) the coolant level slowly rises in the tank, eventually overflowing and bubbling

. It looks like the bubbles are coming from the coolant system, and it's a few quarter sized bubbles every few seconds. Hard to tell if they contain vapor or smoke, but I assume one or the other because when engine is killed, the water level drops followed by more definite vapor (can't tell if smoke or steam) exiting the tank. It's a little whispy, but keeps coming out for a little while after the engine is off... Is ANY amount of vapor normal here?? I'm really hoping it just needs to be burped more.

3. Since that overheat she went well above 100 once more on the way home from work (again only after the turbo boosted), but I was able to keep it from reaching 120. Just prior to that my check oil light started coming on. Steady for a few minutes, then off. I changed my oil and filter three weeks ago and the light has been consistently off since then... It came on again this morning while I was driving up and down some hills to try and burp air bubbles.. Oil level is normal on a level surface after letting engine cool for a minute.

4. I have NOT seen any signs of oil in the coolant or coolant in the oil yet such as dirty looking or foamy coolant or brown/whitish foamy liquid around the oil cap. (other then the check oil light, that seems like a likely indicator?)

5. I'm pretty sure the car hasn't lost any power.

What else should I check, I'm starting to freak myself out..

Thanks fellow tinkerers.

beanybean

tjts1 · #2 10-19-2012, 01:47 PM

I think if you have visible air bubbles coming out of the cooling system its game over. It could be that you have some air still trapped in the system from the water pump change. Did you also replace your thermostat? My stock 80c thermostat didn't fully open until about 98c when I boiled it. Maybe your's is even worse shape?
If it makes you feel better, I'm also living with a #14 head. It holds cold pressure but I haven't seen bubbles and it has no over heating issues on long steep hills or sitting in 90f LA traffic. I feel a lot better about all this knowing I have a good #17 head safely boxed up in the garage. Maybe its time to start shopping.

pimpernell · #3 10-19-2012, 02:32 PM

I would suggest letting the engine cool down overnight. Before you start the engine, feel the radiator hose. Immediately upon starting the engine, feel the hose again. If you have instant pressure in the hose, you probably have a head gasket leak which is allowing combustion gasses to enter the cooling jackets of the block.

Beanybean · #4 10-19-2012, 03:16 PM

Not from overnight cold, (I drove it around early this morning), it takes about 45 seconds after starting for the radiator hose to build pressure, and at most it's medium stiff, you can still squish it a bit.

I did not replace the thermostat.

Beanybean · #5 10-19-2012, 04:36 PM

Also, I forgot to ask - how do I find the head number stamp? I have no idea right now if this is a #14 head that gets all the bad rap...
**Edit**: nvm found it - my numbers are: 603 16 14 01

Which pair is it, 16 or 14...?

Zulfiqar · #6 10-19-2012, 04:43 PM

if you simply poured the coolant mix into the engine and into the overflow tank you will still have air pockets, the only way they expel out is when the thermostat opens up, if you look closely you can see a stream of bubbles or foam at the hose pipe connection of the expansion tank. your fill cap should be off at this time and you should also pump the hoses with your hands to expel air.

I once filled like you wrote and had an air lock which was causing high temperature.

Beanybean · #7 10-19-2012, 04:52 PM

Quote:

Originally Posted by Zulfiqar

if you simply poured the coolant mix into the engine and into the overflow tank you will still have air pockets, the only way they expel out is when the thermostat opens up, if you look closely you can see a stream of bubbles or foam at the hose pipe connection of the expansion tank. your fill cap should be off at this time and you should also pump the hoses with your hands to expel air.

I once filled like you wrote and had an air lock which was causing high temperature.

When I try this it never-endingly overflows.. Maybe I have the reserve tank too full? I don't really see a fill line, unless it's the rib in the plastic that goes around the tank? I'll go try it again on a slant and catch the overflow in a tub, see if it eventually stops bubbling. brb...

Beanybean · #8 10-19-2012, 06:48 PM

Quote:

Originally Posted by Beanybean

Quote:

Originally Posted by Zulfiqar

if you simply poured the coolant mix into the engine and into the overflow tank you will still have air pockets, the only way they expel out is when the thermostat opens up, if you look closely you can see a stream of bubbles or foam at the hose pipe connection of the expansion tank. your fill cap should be off at this time and you should also pump the hoses with your hands to expel air.

I once filled like you wrote and had an air lock which was causing high temperature.

When I try this it never-endingly overflows.. Maybe I have the reserve tank too full? I don't really see a fill line, unless it's the rib in the plastic that goes around the tank? I'll go try it again on a slant and catch the overflow in a tub, see if it eventually stops bubbling. brb...

OK I parked nose up on a hill after some hill-driving to open the thermostat (at least 90), and let the reserve tank overflow line go into a tub. Then squeezed the lower radiator hose vigorously while idling with the coolant cap off. It still overflowed, and by holding down the radiator cap upside down with a piece of paper between I could force the overflow to go into my tub instead of out the top and down to the ground.

I saw the bubbles you mentioned coming in the reserve tank hose pipe, but coolant was also coming in steadily until it rose to the top.
Squeezing the lower radiator hose seemed to slow the water rising, but it would eventually overflow no matter what and I'd have to jump up and either force it into the tub or cut the engine..

I decided to let it overflow into the tub and hopefully bleed all the air out... Instead it pumped all the coolant into the tub (definitely more than a gallon before I cut the engine to avoid another overheat).
Then I refilled, first filling up the engine block, and then filling up the radiator using opposite ends of the big topside radiator hose. It took all the tub coolant plus another .5 gal DI h20.

Same behavior at idle.

Agh! I can't wait for the new fan clutch to see if that's all that's causing the high rpm overheating!

jay_bob · #9 10-19-2012, 07:03 PM

Here is how vstech and I filled my 1987 300TD

When we filled the radiator we found it was beneficial to raise the front of the car on stands and fill from the detached upper radiator hose. We detached the heater hose at the intake manifold and poured in coolant to the upper radiator hose into the block until coolant ran out the heater hose port then hooked up the hose again. We unplugged the aux pump and jumped 12 V to the connector to help circulate the coolant into the heater core. (Pin 1 is + or the pump runs backwards)

Note your mono valve is designed to flow when the valve is unplugged or the car is off so the coolant should make it all the way back through the heat core and the mono valve using the pump trick. Unhook the hose on the forward side of the mono valve and be sure you have flow.

To your point on the reserve tank, the max fill is the rib.

vstech · #10 10-20-2012, 12:26 AM

and even with an underfilled motor, it should not pump coolant out the expansion tank at idle... I'm worried for what that could mean.

barry12345 · #11 10-20-2012, 02:56 AM

As Vteck states it sounds like you have a real problem either with the head gasket or a cracked head. Forty five seconds is just too short a time for the upper radiator hose to harden up from a cold engine.

Beanybean · #12 10-20-2012, 02:25 PM

Quote:

Originally Posted by barry12345

As Vteck states it sounds like you have a real problem either with the head gasket or a cracked head. Forty five seconds is just too short a time for the upper radiator hose to harden up.

Is opening up the engine is the only way to differentiate blown gasket vs cracked head vs both?

If it's just the gasket I'd be interested in doing the job myself (+10 to Mechanic Skill!), but if it's a cracked head I think I'll want to find some assistance.

R/R jobs I've done before are: rear axle, starter, and transmission (with sbean) on the old '80 300TD, and then the water pump and fan clutch on this '87 td.

Advice anyone?

Beanybean · #13 10-20-2012, 03:13 PM

Quote:

Originally Posted by barry12345

As Vteck states it sounds like you have a real problem either with the head gasket or a cracked head. Forty five seconds is just too short a time for the upper radiator hose to harden up from a cold engine.

I think I just had my reserve tank too full. (I hope..)

This morning I cold started to check how fast the pressure built up in the radiator hose (It had held some pressure over night but wasn't hard) It took about a minute to for a noticeable change from semi-firm and squeezable to less squeezable but never hard..).

Then I got it up to temp by driving a short distance, parked and took the radiator cap off @ idle - it released a bunch of pressure and then stayed right at the rib line... No rising level or overflowing at all. I had definitely been filling the tank too full (just a bit below the cap).

Here is a video of the vapor coming out of the reserve tank right now. I can't smell anything other than coolant-smell.

1987 300td coolant reserve tank vapors at idle - YouTube
I hope the mightiest of hopes this looks normal to you guys.

edit** Now the only concern is why did the check oil light start coming on..
Thanks again,
beanybean

barry12345 · #14 10-20-2012, 06:42 PM

Buy, beg or steal a hydrocarbon presence test kit. Test the coolant for exhaust components or hydrocarbons present in it.

I have no ideal what those test kits go for in the states. Ten dollars or so hopefully. I have been thinking if I have or have not noticed a vapour escape on normal engines. Really close to boiling perhaps some might be there is all I can think. Some member will post the information with a better memory though I hope.

If you saw any fairly continious bubbling when those vapours were present it is fairly conclusive they are abnormal. Testing at idle with no load is different than what may be occuring under heavy driving load and increased revs.

There probably is no way to get a diffinitive answer to the head gasket versus a cracked head usually. Although it seems that with a cracked head the coolant system can sustain pressure overnight. Personally if I was not sure I would do the hydrcarbon presence test though. Besides dealing with a replacement head itself I see no differeance otherwise between dealing with a head gasket and the old head versus a replacement head from a time and difficulty perspective.

dagObx · #15 10-21-2012, 02:27 PM

I've heard that the check oil light sensor fails on these engines. I know mine did & the replacement one wasn't too cheap. I suspect that is the problem, especially if the oil in the engine remains full on the dipstick. I wouldn't completely ignore it, but would change the sensor out as soon as you can for peace of mind...