Paul5388

I've about run out of ideas on this and hope someone has additional information or a solution.

So far, I've installed a new radiator, new thermostat, new water pump and a new fan clutch. Today, I drove about 30 miles on open highways without any temperature excursions, until I got into town. By the third traffic light, the temperature reading was close to 120 C or above. That curtailed any further shopping sprees and after a 30 minute stop, we headed home.

The return trip only saw the temperature getting up to about 100 C.

I think the ambient temperature was around 93 F.

I'm beginning to think the gauge isn't being truthful, but I'll probably check it with an infrared thermometer at different levels of temperature readings.

What am I missing on this deal?

Here's a picture of the car that still shows 173K miles after owning it for three years.

Paul5388

I checked the temperature this afternoon in several locations. The radiator never got off of 30 C. The housing that would be for the thermostat on a normal car (upper radiator hose connects to it) read 78 C at the sensor location, but 45 C just an inch toward the radiator hose. That, to me, indicates there's a blockage to the flow of coolant in that area.

Does anyone know if there's a secondary thermostat, besides the main thermostat just forward of the right hand motor mount?

Paul5388

I took the upper radiator hose off today and there's nothing to block the flow in the elbow, but there is a flow blockage somewhere and about the only thing left is a defective Stant #13588 thermostat (made in China and it isn't an exact replacement).

I'll order a Wahler 80 C with a new "O" ring and go to the trouble of changing it again. I did check the original in a pan of boiling water and it did open at about the right temperature.

Sathinas

Blown headgasket maybe?

Paul5388

I don't think so, but it may have happened even though I never did let it get super hot. Normally, a head gasket will allow pressure into the cooling system even if it isn't up to temperature.

There's also the 14# of coolant pressure that many times will leak into the cylinder(s) after the engine is stopped. That usually can be seen, smelled, tasted (antifreeze vapor from the exhaust is a sweet taste and the sweetness is why dogs drink antifreeze) and seen on a radiator pressure leak test. Since the leak test is done without the engine running, I'll probably check that tomorrow.

Sathinas

Ah... Common misconception. You could have a blown headgasket and your cooling system will never over-pressurize.

Did you check the lower radiator hose? I've personally never seen a completely blocked off radiator hose, but I have seen blocked off water passages in the engine.

Try a leakdown test and if that comes back "good", then try running a garden hose in the top radiator hose (make sure your thermostat is open) and see if you get returns through the bottom hose.

Paul5388

I closed my repair shop in 1987, so it's been a while since I've had to stretch my brain on troubleshooting and most of it was on Japanese vehicles or VWs. Bouncing ideas and suggestions back and forth certainly helps in the process.

Since the lower radiator hose has positive pressure from the water pump on it in this application, I would think it would be highly unlikely for it to collapse. That's not right, it has a suction on it, or it depends on head pressure from the coolant column.

You're absolutely right about a blown head gasket possibly not leaking into the water jacket. It will, however, leak somewhere. Either into the oil passages, and make an oil/water emulsion in the radiator, or it will leak somewhere that is inconsequential (if a compression leak can ever be that). None of those leaks has anything to do with the cooling aspects of the engine, especially since the radiator doesn't have any oil in it.

If the compression ratio is 20:1, there will be 290+ psi leaking, and if it gets into the cooling system, the radiator cap cannot hold that pressure.

Paul5388

As I expected, the radiator check, pumped up to 13 pounds, held steady.

We'll know in a few days whether the new Wahler thermostat will fix the problem.

David Hendy

I bet you have a cylinder head that has cracks between the valve seats.

You probably need a new head.

What is the casting number on the head?

Paul5388

I don't have any idea what the casting number is, mainly because I don't know where it's located.

David Hendy

On the drivers side of the cylinder head, immediately below the the intake runners for cylinders 2-4, therer will be a number.

The number has the format 603-016-**-01

The third section of numbers is important. The early heads were number 14. If its a 14 its an original head then you are toast, and you need a new head or a new engine.

There were 6 casting numbers as I remember, with more & more upgrades from the factory. 14-16-17-20-22.

A number 22 head right now bare, is about $3K I think.

The number 14 heads are awfully susceptible to overheating. Once it starts you are done. The early heads had quite a lot of combustion chamber in the head. The latest heads are just plain flat.

I've parted out 10-12 603s in the last 2 years. 25% had cracked heads.

Paul5388

Yep, it's a 14, but I think I'll reserve judgment until the new thermostat is installed.

I suppose you know cracks can be repaired?

David Hendy

I really hope that the thermostat fixes it.

If it doesn't these heads are nearly impossible to weld. Easier to find a known good head. I have sold good #14 heads for $400-$500. I sold a #20 head for $1200.

In Texas I'd run 25/75 MB Coolant & distilled water, 2 cans of water wetter or purple ice, buy a new radiator, a new fan clutch & run my aux fans ALL the time.

I love the '86-'87 diesels & the 603 engine in general, but the early heads are a problem, I mean they crack in the New England heat!

Good luck

Paul5388

A local shop has been "lacing" cracked heads for 25+ years. The process involves screws that are threaded into the head at close intervals and then grinding the screw heads off.

I have already replaced all of the items you listed plus a new water pump, but the radiator was replaced due to a leak, not because it was running hot. The normal operating temperature has always been slightly above 80C.

If the newer heads are flat, the pistons would have to be changed to accommodate an increase in compression, or head shims would have to be used, like VW has done since the 1980s with their varying head gasket thickness.

David Hendy

If you go over to the board at peach parts (www.peachparts.com) you will find a whole crew of people who know way more than I do (the little I know I learnt on that site).

I have sold several blocks (from engines with cracked heads) to guys with 140 s class 350SD or S350D's (the rodbenders). They put their newer (number 17 or later heads) on the early blocks. What they have done is shim the injectors and the engines run fine.

Paul5388

David,

You're probably right about the crack. The car runs without radiator bubbles, until it heats up to operating temperature. The heat is sufficient then to widen the crack and let pressure into the cooling system, creating coolant geysers.

My local shop says they need to see the head before they can tell if it's repairable and definitely not if it's cracked into the port.

My temporary solution was to buy a 1996 E300 with a 606 engine. It sure doesn't have the power of the 603, but maybe it'll be OK after I get used to 1200 cc VW power.

David Hendy

Damn thats a shame.

You know its probably just a parts car now. Sell the turbo ($300-$400), IP ($300-$400), trans ($300-$600) & rear diff ($200) and some of the other easy to harvest parts ($500-$1000 total) and junk the rest.

Paul5388

Can the turbo on the 603 be used on the 606? It sure needs a little boost.

David Hendy

No but I'm pretty sure the turbo from a '98/'99 E300TD will work as that has a 606 engine as well.

Paul5388

I'm making a trip to St. Louis later this month and will see what I have as far as economy and power. I suppose economy is the major factor, since it seems to do well enough on East Texas hills at cruising speeds. The Ozarks may be a little more challenging between here and Little Rock, but it'll all be interstate driving, which will help too.

I don't know if I have enough fuel on board to go the whole 641 miles without refilling, but at my age I don't know that I want to drive that long without a break.

oldbeaver

Paul5388,

More than two years later, but your post is still catching attention: mine.

I hope you solved the overheating issue in yr 603 MB?

Did you get the german thermostat?

Do you know what is the normal operating temp of this car?

I bought a similar car recently and am not sure if my temp is normal or not.

Best,

Oldbeaver

compress ignite

oldbeaver,

You have PM traffic,with links.

Normal Operating Temperature for the 5 Cylinder Turbo-Diesel should be in
the 80 Degree "C" range. (90 degrees "C" would not be alarming, under Load).