Compact overheats until the hood is opened...

So on behalf of a family member, who is technically savvy, he has a 2012 Wacker Neuson 28z3, S/N AG05746, somewhere near 500hours from new.

After about 30/40mins the 28z3 sounds the engine temperature alarm, once i open the engine cover the alarm stops after a minute or two with the engine still running

Diagnostics so far...

1. Blown out the radiator to ensure that it has airflow, radiator fins all in like new condition
2. Verified the radiator fan by verifying that a piece of paper will 'stick' to the radiator thus confirming airflow
3. Removed the thermostat and ran the machine to see if the condition re-occurs, which it does
4. I have confirmed it is a genuine overhead rather than a sensor issue by measuring the temp of the thermostat body when the alarm goes off...saw approx 235deg
5. When removing the thermostat did a visual check of the thermostat housing and inside radiator filler which did show any residue or debris inside the cooling system, it all looked just like new...the coolant was clear and like new
6. The engine cover is in good condition and the front and rear vent's are as designed and not blocked or modified

The hydraulic filter was changed about 20hrs ago, the engine oil and filter changed 5hrs ago, and the air filter is clean. There are no obvious signs of any modification or prior repairs and the machine is fully functional..the machine is I believe 2012 and has 540hrs on it. The typical air temp during these time when the alarm sounds is 80-90deg

I've pondered this and can't seem to figure it out... runs hot till the hood is opened...? WTF

Anyone seen anything similar?

Pictures? It's small, it's tight, it's all insulated, there's not enough venting of the engine compartment air. Is the muffler wrapped? Where is the air cleaner pulling it's air from, inside the compartment? Altitude? Air baffles all in place around the radiator? Those little Yanmar engines are usually bulletproof.

Message passed on...
Pictures and more info to follow...
Agreed in your last point, little yanmar engines are usually bullet proof!
Altitude... It's in Sacramento area so not exactly super high.

No, not high, I would be looking for 10,000 feet before it started cooking usually.

Is there a hydraulic oil cooler in front of the radiator? Is the hydraulic oil getting equally hot?

I'd really flush the radiator out good with a garden hose from both sides. Between the oil cooler and, ac cooler it is tough to blow them all out the way there stacked in there. You'd me amazed how much dust and dirt can pack in there that you might me missing with a blow gun.

I had one that would run hot with the hood closed ck every thing ended up the fan just was not turning fast enough even though it seemed to be I put a fan hub on it and it was fixed

Yair . . .

It is obviously an airflow issue . . . anything changed where air exits the engine bay, a piece of insulation come loose perhaps and causing some obstruction?

The point I make it doesn't have to be on the upstream side.

If it has a viscous drive fan the first thing would be to lock it up and check belt has not worn down into grooves.

It will be interesting to see the outcome.

Cheers.

Make sure the fan is not on backwards and all the foam / gaskets around the radiator are good,

500 hours is a good time for the belt to get loose. Did the overheating start before the oil changes? or after?

Use to be a nearby company called "Huber reversible Fan Company",

and they claimed you would reverse their blades for winter/summer.

Can't really see it making a difference unless the airflow ran thru the cab.

The reversible fans have/had reversible blades. Turning a normal fan around won't reverse air flow, it just makes the fan horribly inefficient and you will have overheating due to low air flow. Something to look at, can't imagine a factory putting a fan on backwards, but you never know?

lantraxco said:

Pictures?...

Click to expand...

The Peej said:

I'd really flush the radiator out good with a garden hose from both sides. Between the oil cooler and, ac cooler it is tough to blow them all out the way there stacked in there. You'd me amazed how much dust and dirt can pack in there that you might me missing with a blow gun.

Click to expand...

Radiator Has been flushed, Was clean inside visibly and clean to flush. Also has been run without a thermostat, Still overheats.

ohiofleet said:

I had one that would run hot with the hood closed ck every thing ended up the fan just was not turning fast enough even though it seemed to be I put a fan hub on it and it was fixed

Click to expand...

The fan hub is fixed.

Delmer said:

500 hours is a good time for the belt to get loose. Did the overheating start before the oil changes? or after?

Click to expand...

The owner/operator has recently bought the machine and has no history on it... so really that is an unknown.

lantraxco said:

The reversible fans have/had reversible blades. Turning a normal fan around won't reverse air flow, it just makes the fan horribly inefficient and you will have overheating due to low air flow. Something to look at, can't imagine a factory putting a fan on backwards, but you never know?

Click to expand...

The fan being fitted backward is something I suggested, on inspection it is offset and therefore can't be fitted in reverse.

Thanks to all for input so far!

I see the hood is adjusted as high as it can go in the hinge slots, is it sealing properly across the top and side when it closes? Also, is there a way to pull that air intake hose out away from the radiator a bit, looks to me like it's blocking air flow. That's so tight in there I think you're looking for a couple degrees at a time.

Is the floor solid under the engine, or is there a provision for some outward air flow there?

Oops typing with elbows again....please dis-regard

man listening to all the things he has tried already, I would say the issue should show itself but it proves otherwise. Maybe try removing the screen in the hood. must be an obstruction somewhere

The hinges being at the end of the slot, and the dent right in front of the battery seem to go together. In one pic the right bolts look like they had been installed at the top of the slot previously and the left side is missing a bolt.

A few things to look at....belt tension is only supposed to be 8mm or roughly 1/4".
Has the cooling system been pressure tested? test to 15psi.
Confirm your rad cap is functioning correctly. test to 15psi.
Your likely culprit is going to be the rad cap.
BTW your coolant doesn't look very healthy. The Wacker machines don't come with the greatest coolant from factory to begin with so I would recommend changing that coolant. Every pound of pressure in the cooling system raises the boiling point 2 degrees. 15psi = 30 degrees. If the coolant turns into steam because of a bad radiator cap is will overheat rapidly. Opening the hood on the other hand is allowing more air flow through the radiator and its pushing air over the engine faster. Never seen a 28z3 overheat because of the location of the engine. One of the best placed engines in its class if you as me.

Let me know what happens. I have worked on my fair share of those machines.

Serpentine belt or V style belt driving the fan ? The reason I ask is I have seen V belts get a hard glaze on them and no amount of tightening would stop them from slipping.

In answer to all feedback to date:
All appears to be correct and serviceable... certainly nothing obvious.
Some have mentioned the radiator cap, seems plausible, its the next stage.
To be tested or replaced and re run.
Thanks to all for feedback.
Results to be confirmed.