Head's on, car's running! - PeachParts Mercedes-Benz Forum

MarkM · #1 04-19-2002, 11:14 PM

Just completed my my first ever head removal and replacement !! While I expect this will solve the moderate blowby (new guides nice and tight), and head gasket problems (should eliminate CO in coolant head space, and oil in coolant. BUT, car still runs on the warm side (95-100C) steady on highway, with some unexplained peaks to about 110C. this happens on highway trip with heat on.

I also put in all new coolant hoses, coolant reservoir cap, oil cooler lines, belts.

Previously, I installed new radiator, thermostat, flushed rad every two years.

Any thoughts on the running temp.??

Thanks Mark

HGV · #2 04-20-2002, 12:49 AM

I am perplexed by your running hot problem. I have the similiar situation on my 87 300td. I have done everything I can possibly think of. I think you we need to check engine exhaust back pressure. Search for my thread about the same problem. I still need to check IP timing and exhaust bck pressure. The car runs well with good power but it still runs hot.

MarkM · #3 04-20-2002, 07:36 AM

I read all of your previous posts and no "smoking gun". I know for sure that the problem on my car is NOT the head, since I changed head (I put on a rebuilt one and sent my core back). The running hot problem is exactly the same as before head removal. The symptoms of this problem are exactly what you would expect with a malfunctioning thermostat (erratic, unexplained peaks, etc.), AND they started on my car exactly when I changed thermostats....before thermostat change, temps were low (70-75C).

Thinking through methodically:

Thermostat - I put in two with no differerence - one was a Behr, one a Febi...no difference. What do i do now? put in a Wahler??? (I do have one but havent put it in)

Radiator: I put in new Nissen (for another problem...suspecting trans. fluid leaks)...before I changed thermostat....car ran cool before and after. Cant be this.

Water pump- pully turns, belts tight, no leaks...I cant imaging this to be the cause.

Blockage in cooling system - I always flushed system every two years, never excess crud....if this, the car would have run hot before I changed thermostat...I cant imaging a bad thermostat so bad that it would mask this mega problem. Thus cant be blockage in cooling system.

Head/Head gasket - just replaced with rebuilt head (pressure tested, magnafluxed etc.), new head gasket...no difference before and after...thus cant be this.

Air pocket(s) in cooling system....the system is designed to eliminate air pocket via a little hole in thermostat housing...I cant imagine that the cooling system was designed so poorly as to require some special trick to get the air out, plus Ive never has this problem with previous coolant changes....I dont buy this one!!

Aux. coolant pump....not related to engine cooling (?)...its designed to provide adequate coolant flow to heater/monovalve when idling. Plus, its operating properly. Cant be this.

Collapsed hose(s) - I doubt it, since I just put ALL new coolant hoses in (preventative maintenance while head was off). No change before and after. Cant be this.

Expansion tank Cap - I just put new one on...no difference between new and old one. Not this.

Heater core, mono valve - not directly related to engine cooling (enging should adequate cool with heater system off) I get good heat, mono valve works great etc. Not this.

Coolant volume - I just drained about 11 1/2 quarts and put in same...total capacity is 13 quarts...even with all coolant drained, there must be at least 1 1/2 quarts remaining....with head off, I could see coolant in block even after draining via block drain plug (car on level ground). Cant be this.

Exhaust system back pressure - ??? I dont know about this. Car runs fine, good mileage on highway (25 -30 mpg), peppy, good acceleration. Restricted exhaust would greatly impact this.

Engine timing - could be, but I cant imaging that timing could be off enough to effect the coolant temp while the car still runs fine with good fuel economy. The cooling system MUST be designed with enough cooling capacity so that you would not see drastic changes in coolant temp. with minor variations in fuel injection timing...I dont buy this one. However, with recent head replacement I didnt check timing (no time, had to work till midnight to get car back on road for the next day) I will check in a couple of weeks, but I dont think this is it.

Coolant temp sensor - I put in new one...no change before and after.

HAVE I MISSED SOMETHING....the only thing left for me to do is to go out and kick the darn thing!

As I said, I'm baffled.

I'll go try the Wahler thermostat later today

regards,

mark

MarkM · #4 04-20-2002, 09:07 AM

Just a day after completing head removal and replacement, I went out this morning (car cold after running yesterday) and felt upper radiator hose...high pressure!! Opened expansion tank cap and major woosh of air!!!! WHAT THE!!!!!

Does it take a few days for the head gasket to "settle in" or should the gasket seal immediately??

Just to address obvious questions, I "chased"all head bolt holes with a die, and cleaned them out, head bolts were all new, greased before installation, and torqued properly in accordance with MBZ manual (40 nM, 70 nm, 10 min wait, 90 deg, 90 deg), and I used a new out of the package Goetze head gasket!!!

I wasnt sure of the mating surface of the new head...it had rough longitudinal striations from one end to the other..appeared to have been machined from one end to the other, but did not have circular "finishing" pattern. I didnt know what I was looking for, but it was different from original.

I still have my old head....the only reason I went with the rebuilt was in the interest of time.

I am totally b.s. and depressed now after this MAJOR effort. If I continue to see this high coolant pressure when engine cold, I guess i will have new valve guides and valves ground on my old head, and pull off the replacement head and send the dam thing back!!!!

It's at times like this when having an old Mercedes diesel, and being a DIYer, really sucks!!! The work is hard, the head is heavy, the work is very messy, it takes a lot of time, and I'm almost ready to throw in the towel!!!!

jcd · #5 04-20-2002, 09:19 AM

We have all been where you've been with some job or another.

Although I can't help you with technical advice, my suggestion would be to take the day off, do something enjoyable and give the technical experts a day or so to offer advice so you can reset your plan.

Again, you have my moral support....hang in there.

JCD

Bear · #6 04-20-2002, 09:32 AM

Mark,I agree with JCD but would wait till monday when alot of the tech's will get back to their computers after a relaxing weekend.Hope you get it sorted.Bear

#7 04-20-2002, 01:01 PM

Well, in my past experience as an auto technician, since you have basically eliminated any other source for the problem, the only thing left is the block. More than likely the deck is warped, or you have a hairline crack in the cylinders someplace. Maybe a cracked liner, and the compression is going up btw the liner and the cylinder wall past the compression ring on the cylinder opening in the headgasket and straight into your cooling system.

Cracks ae usually pronounced when the engine is cold and will build excessive coolant pressure with in 30 sec of starting the engine.

My suggestion is to remove and completely disassemble the engine and send the block to be cleaned, pressure checked and magna-fluxed.

There isn't any other possibility, you could bypass the entire heating system and have the engine not run hot.

I'm assuming the coolant senser you replace was the one in the side of the head next to the GP temp sensor. The one in the t-stat housing is for the aux. cooling fan.

Exhaust back-pressure won't have an affect ont he engine temp, except maybe to make it run cooler. You won't have any power because the pistons have to force out the exhaust gases and some stay behind causing cooler combustion temps.

Injection timing may affect it, but not like you are having.

Pressure in the cooling system like that is your clue, combustion is getting in there somehow....They make a tester to check for CO and NOx in the coolant....I can't remember what it is called....works really well.

Good luck!

harrywat · #8 04-20-2002, 04:56 PM

Mark

A fast and simple way to confirm combustion in the coolant is remove the water pump belt, so it can't operate. Remove the thermostat and top that area off so you can see the coolant. You may have to rotate a hose upward. Tie the fuel shut off down so the car won't start.

Best done with a warm engine. Have someone crank it over while you look for bubbles in the coolant.

If you have bubbles, you can narrow the location by removing injectors until there are none.

Harry
86 300 SDL

psfred · #9 04-20-2002, 05:01 PM

Intermittant temp spikes and running slightly warm is what I get on the old 220D when I'm low on coolant -- it dissapears and I've not found the leak yet (I think it is the rad).

You may not have gotten all the air out yet -- refill and run a bit with the expansion tank cap loose and see if the level drops, the refill and re-check pressure.

The head doesn't have to be perfectly flat to seal, but I'd not put on one that had distinct catch-your-nail grooves it in for fear the gasket wouldn't compress enough to seal. Normally reconditioned heads, if machined, are very smooth.

Peter

anhydrous7 · #10 04-21-2002, 03:16 AM

I tend to agree with pfred. It sounds like you may have air trapped in your cooling system. It is always a good idea to loosen or remove the cap and run the car when filling the coolant system. Better yet, I use a kit that allows you to place a substitute cap on the radiator that enables a plastic fitting to stick up through the center of the cap. There is a bowl that then fits into the fitting, thus allowing you to run the vehicle while being able to add coolant and allow the air to escape from the system and not cause a great mess. Most better parts stores should have these.

Good luck!

Rob

gsxr · #11 04-21-2002, 06:19 PM

Mark,

Sounds like my project, except I have the OM603 instead of the OM617. I just replaced my head (was cracked) and now it runs hotter than before. I also have checked the same list of items you had, all are OK. Before the head was cracked, the car had ZERO pressure when cold, sometimes a vacuum. I noticed the high cold pressure last fall and spent Feb+Mar replacing the head. I just got it running last week. I now get slight pressure when cold.

For grins, I even squeezed the upper hose and screwed the cap on, to force a vacuum in the system. The next day the hose was less collapes, the day after there was no pressure, day after that back to slight pressure. It seems to build up slowly (unlike before, with the cracked head, it would build up fast.) I'm guessing either the gasket didn't seal (due to imperfect block sealing surface), or as Brandon said, a problem with the block (cracked liner?). I think I'm losing a small amount of coolant too - haven't gone far enough to tell yet (only ~300 miles).

My car runs hotter than before, but not so hot that it's a problem. It's hit 100C several times in cool ambient temps, normally it never gets to 100C unless it's 100F outside (currently 50-70F). I'm pretty much stumped (and tired, and generally PO'd.) I won't even get into the weird oil drip from the #6 exhaust manifold port...

**sigh**

#12 04-21-2002, 09:05 PM

To add to my previos post, I thought of something regarding your thermostat....

Mark, when you said that maybe the old thermostat was masking a bigger problem, maybe it was.

When thermostats get old, they tend to react slowly and stay open longer allowing cooler engine temps. Maybe when you replaced thermostats, the coolant temp is fluctuating to the exact temp. Now with a working t-stat your engine is running hotter revealing a problem that you've probably had for awhile, just didn't know it due to a poorly operating t-stat.

My car ran around 150-160F before I replaced the tstat, and around 190F after the tstat which is normal operating temp.

Something else to think about....

MarkM · #13 04-22-2002, 10:25 AM

I ran the car with the coolant cap off, then on, then off...etc....no drop in coolant level, therefore I dont believe there is air trapped in system.

Much worse......the car generally runs at around..... 95C clearly not hot enough to boil coolant. But if I stop the car and open the coolant cap, I get major release of pressure, bubbling up of coolant and some loss through overflow tube. If I put the cap on, drive for another 5 minutes or so, same thing. This means there is serious exhaust gas getting into coolant.

When car is cold next morning, there is high pressure in system (hard rad. hose, big woosh when opening coolant cap.)

The running hot symptoms are similar to before, except that I did not previously get high pressure in coolant system.

Pressure builds in the system relatively slowly while driving at 60 - 70 mph. Not fast within 30 seconds of starting..therefore I dont believe there are cracks in block, sleeves etc.

I believe that the source of the problem is the mating surface of the new head....it had "fingernail-catching" grooves across the entire surface of the head, all running in the same direction from front to back. Whereas previously I believe I had minor failure of head gasket, I think that now I am getting combustion gases from each cylinder getting into the coolant passage between cylinders.....gasesare passing through the grooves in the head. The distance from the cylinders to the coolant passage between cylinders is only about 1/4 to 1/2 inch....very close. And the grooves are running in the correct direction to do this.

I think what I am going to do is this:

1. Pull off replacement head and return it for money back.

2. Take my original head and have it checked...I will have all new valve guides and seals installed. I dont believe it is warped and the valves look very good....I think I will leave the mating surface alone, and just lap the valves myself.

Any thoughts???

Thanks,

Mark

gsxr · #14 04-22-2002, 10:53 AM

Mark,

I was thinking the same thing on mine (see previous post). However, what will you do about the block surface? I scuffed mine with sanding sponges and did a final with Scotch-Brite (which was a bad idea, it starting coming apart). The surface *looked* fine. And my head was brand new. I have similar post-operative symptoms (running hotter than normal, and pressure in cooling system - less than yours though). Are you planning to pull the engine and have the block surfaced?

Thanks for sharing your story, btw!

Regards,

MarkM · #15 04-22-2002, 11:19 AM

I think i will just leave the block alone, but Im not sure. I will pull off the head, look extra closely at the block (but I already meticulously went over the block before). If there is any slight imperfection, I will sand out. Also I will get a good straight edge and check for true.

At this point i wonder if I do all this, am i going to see much the same thing??!! I dont have the capability to pull the engine and rebuild (no garage, etc.). Plus, this car is not a "project car", but my daily driver. So, if I go through all this and see similar behavior, I will probably drive it til the natural end of its days (the car may live for years with a minor handicap!!).

(What is really frustrating is that I have completely rebuilt the suspension, AC, put in new axles, a new rear trailing arm, motor mounts, and many, many other things, thinking I could run the car for another 10 years)

Gook luck,

I'll keep you posted.

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