Changed out Thermostat and temps keep rising.

Before my theromstat stuck open its running temperature was around 90 degrees C all day every day. I spent today fitting a new thermostat and a couple of other things including a new aux water pump for the D5 Hydronic so i drained the system down completely. After i'd finished the work i filled the coolant circuit up with Comma G48 ready mixed coolant thats approved by Merc to their 326.0 standard.

First impressions, the cab was now toasty warm after five minutes driving which it wasn't with the broken thermostat but rather worryingly the temperature rose to 110 degrees C when under load. I've never seen temperatures like that all the time i've owned the van (14 years).

Should i be concerned? There are no leaks anywhere in the engine bay the part although not OEM is identical to the one removed, the old coolant looked in good nic - no debris so i'm wondering if it'll settle down after a while or whether theres another problem.

Any help greatly appreicated.

Roger

I am not sure about your particular problem/sprinters but aftermarket thermostats in general can come set to open at different temperatures. Can you check what the one you purchased is set at? I noticed a similar thing when I did mine. 180F on old tstat and now 190F. 110C does sound a bit on the high side. Sometimes air can get trapped in the system causing high temps but I havent heard that being an issue in sprinters (it's very common in the VW world)

Njclimber said:

I am not sure about your particular problem/sprinters but aftermarket thermostats in general can come set to open at different temperatures. Can you check what the one you purchased is set at? I noticed a similar thing when I did mine. 180F on old tstat and now 190F. 110C does sound a bit on the high side. Sometimes air can get trapped in the system causing high temps but I havent heard that being an issue in sprinters (it's very common in the VW world)

Click to expand...

It was a Wahler unit i purchased and was identical to the original merc-stamped part it replaced, both had 87oC stamped on the physical valve that opens and shuts so thought nothing of it.

I did wonder whether i had an air lock as at present i have the dashboard removed and could clearly hear gurgling from the heat exchanger in the centre back of the dash so wonder if it may settle or whether the circuit needs burping. I squeezed on the main hose that connects to the rad below where you fill and got a few air bubbles nothin major.

In all the coolant circuit has taken 8.5 litres to refill. Think i'll keep a watching brief to this.

Under load 110*c is not a big worry, quite common.
Any more than that, downshift to raise RPMs and increase heat removal.

NelsonSprinter said:

Under load 110*c is not a big worry, quite common.
Any more than that, downshift to raise RPMs and increase heat removal.

Click to expand...

Cheers NS i've never really taken much notice of the temp guage in all the years i've owned my van as every time i've looked at that part of the binnicle its permanantly at 90oC. FWIW i just gone out for a quick blat of about 10 miles with plenty of hills and a couple of long straights and the running temperature is about 95oC so not all that bad.

Its quite funny, having repaired my cab heater recently (green cable) after being broken for about 8 years and this new thermostat the cabs like a sauna in about 5 minutes of getting in, unbelievable!

https://photos.app.goo.gl/feGyo6VxpGCycSQW7

going to 110c regularly can be a sign of problems... unless of course your regular day is hot (37c+) with a long steep grade.

Low hanging fruit would be to replace the viscous fan clutch at minimum. If the serp belt hasn’t been replaced in a while I’d change that out along with the belt tensioner and idled pulley. If the belt is wobbling badly while the motor is running change out the alternator pulley/clutch assembly. A non-smooth running serp belt circuit due to the alt pulley failing will also make the belt tensioner crap out and then possibly make the v fan/clutch assembly and water pump not operate correctly.

There’s also a chance you dislodged some junk in the coolant circuit when flushing the system and now it’s lodged somewhere else impeding coolant flow.

I'll give you the old school approach to radiator/antifreeze/thermostat R&R.
This isn't the Benz way most likely but I did it anyway when I did mine this summer.

Fill the radiator and run the machine at idle with the cap off until you see evidence of circulation and the coolant is hot.
This eliminates most airlocks.

Cap the system and go for a drive.

Stop along the way and with a towel over the cap gently uncap the system running and have another look. It should be hot but all hell should not break loose.

All good?, but probably the level is a little low so top up but not too much.

Don't top up when the coolant is cold . You will just force it out the cap when the hot expansion happens.

It's always nice to check your temp gauge with a thermometer stuck in the radiator fluid.

After a few runs the radiator will find its own level. Respect that, don't force it to be too full.

Use a funnel or you will just make a mess. You won't see leaks.
Watch for leaks.

If you had hoses off retighten clamps 1/2 a turn even if they didn't leak.
Consider a new radiator cap and carry the old one as a spare.
Get the correct pounds/pressure.
The system has to be under pressure or it will run hot since water boils at a higher temp under pressure. You need a good cap.
(Did I say that right?)


bill in tomahawk

billintomahawk said:

I'll give you the old school approach to radiator/antifreeze/thermostat R&R.
This isn't the Benz way most likely but I did it anyway when I did mine this summer.

Fill the radiator and run the machine at idle with the cap off until you see evidence of circulation and the coolant is hot.
This eliminates most airlocks.

Cap the system and go for a drive.

Stop along the way and with a towel over the cap gently uncap the system running and have another look. It should be hot but all hell should not break loose.

All good?, but probably the level is a little low so top up but not too much.

Don't top up when the coolant is cold . You will just force it out the cap when the hot expansion happens.

It's always nice to check your temp gauge with a thermometer stuck in the radiator fluid.

After a few runs the radiator will find its own level. Respect that, don't force it to be too full.

Use a funnel or you will just make a mess. You won't see leaks.
Watch for leaks.

If you had hoses off retighten clamps 1/2 a turn even if they didn't leak.
Consider a new radiator cap and carry the old one as a spare.
Get the correct pounds/pressure.
The system has to be under pressure or it will run hot since water boils at a higher temp under pressure. You need a good cap.
(Did I say that right?)


bill in tomahawk

Click to expand...

Cheers Bill thanks for your advice.

Been out in it a couple of times today and its running temperature is about 95C, with the old one it was a bit less. Left it idling on my driveway for 30 mins and was rock solid at 95C so will live with it. I did check the levels and they were unchanged from yesterday so i dont think theres an airlock per se.

Also had a read of the owners handbook in the section marked 'coolant' and its suggested running temperatures are between '85C and 120C depending on coolant and environment so feel a little better.

I've had the serp belt done just before christmas but did notice on further investigation the left hand pulley oscillates noticably so thats the next job, (pulleys and tensioner) will take a look at the fan at the same time.

Cheers

Only here to reiterate the importance of a properly functioning viscous van clutch. I replaced mine whilst troubleshooting what I thought were abnormally high operating temps, and it completely resolved it. Now I can run up grades with the a/c on and maintain just a half notch over 180. It may not be your issue of course, but it was a lesson for me in how integral they are to proper engine cooling...

Well that's a lesson learned. Bit the bullet and bought a genuine Mercedes thermostat and whadda you know? Overheating problem solved.

When i compared the two units they look the same but a couple of things stood out on closer inspection. The first unit i bought that was sold as a Wahler unit, it clearly wasn't as there was no manufacturer id/markings on the casting whereas the OEM Merc part is stamped 'Wahler' and the quality of the casting is head and shoulders above the other unit.

The two parts



Also in the back of the thermostat housing on the Merc part is what looks like a brass tube with a ball bearing that moves, the other unit had no such sub-assembly:

Here's the Merc one with the extra sub-assembly in the top-right back of the housing in this picture



And the offending part without



Cylinder head cleaned up before refitting the new part.



So after flushing the engine out and replacing a load of manky jubilee clips with new stainless ones I refilled with G48 coolant and took her for a spin. That included going through the gears going uphill and down dale and also sitting in a bit of holiday traffic for a few minutes and she didn't budge from her 87oC just like the old days so i'm well chuffed with that.

On the shopping list next is replacing the hoses to and from the radiator/water pump & thermostat plus the ones that run up to the heater matrix as they all feel flimsy and a couple are showing signs of perishing but that can wait until i have the front off in a couple of months to do the pulleys.

Cheers

Counterfeit parts are a common occurrence, especially in the euro market. I try to buy from long term dedicated outlets, or the dealer. Pop-up stores on ebay etc, just buy whatever from whoever, and don't often due the diligence to keep fakes out. Of course even major retailers can still get counterfeit parts on occasion. The only exception is the dealer network, as they generally have supply chain visibility from factory to shelf.

Not that you asked...

rogerball0 said:

...

Also in the back of the thermostat housing on the Merc part is what looks like a brass tube with a ball bearing that moves, the other unit had no such sub-assembly:

Here's the Merc one with the extra sub-assembly in the top-right back of the housing in this picture

...
Cheers

Click to expand...

This part?



If yes, it looks like the "Jiggle Valve". The purpose of that part is to allow a low flow of coolant to circulate through the thermostatic valve assembly when the element is closed. Without that flow the element doesn't heat up to properly open when needed.

I believe that that the lack of a jiggle valve would explain your symptoms/problems. It a common design part for many vehicle thermostatic valves. Leaving it out was a real boner of a mistake on the part of a pirate part producer... assuming that is what happened. (I have no reason to doubt it is a pirate part.)

Added:
Further pondering...
In some makes/designs, it isn't uncommon for a jiggle valve to be included into the thermostat element tin flange. Not that it really matters. That just popped up from my memory.

Thanks for the update.

What Midwesterndrifter said about parts suppliers FWIW.

vic

Midwestdrifter said:

Counterfeit parts are a common occurrence, especially in the euro market. I try to buy from long term dedicated outlets, or the dealer. Pop-up stores on ebay etc, just buy whatever from whoever, and don't often due the diligence to keep fakes out. Of course even major retailers can still get counterfeit parts on occasion. The only exception is the dealer network, as they generally have supply chain visibility from factory to shelf.

Click to expand...

Yeah its something that increasing irritating here in the UK where what you order isn't what you necessarily receive. I've found a couple of outlets now online that specialise in sprinter parts so will stick with them in future. The other observation with non-oem /pirate part stuff is how little difference there is in price - a no brainer going forward.

Aqua Puttana said:

Not that you asked...


This part?

View attachment 111934

If yes, it looks like the "Jiggle Valve". The purpose of that part is to allow a low flow of coolant to circulate through the thermostatic valve assembly when the element is closed. Without that flow the element doesn't heat up to properly open when needed.

I believe that that the lack of a jiggle valve would explain your symptoms/problems. It a common design part for many vehicle thermostatic valves. Leaving it out was a real boner of a mistake on the part of a pirate part producer... assuming that is what happened. (I have no reason to doubt it is a pirate part.)

Thanks for the update.

What Midwesterndrifter said about parts suppliers FWIW.

vic

Click to expand...

Yep thats the part Vic, its made all the difference. The last couple of weeks (with paid-work far from home) really tested my confidence in the van. I've been driving with one eye on the guage and one on the road with the heater on full tilt, it reminded me of owning a Fiat in my student days

Just spent the morning pricing up all the water hoses - all Febi-Bilstein stuff and that comes in at £70 the lot, I'm gonna cross check that with the dealer during the week. Its funny - the more i crawl around my engine bay the more i see needs doing.

Still if it saves big bills ahead its worth doing.

Cheers

Roger
The answer is to buy parts from an MB dealer.
Then you will be spared these parts fiascos which can fail or not be to spec (as you have discovered) and do serious damage to your van.
Junk is expensive at any price remember.
Dennis

lindenengineering said:

Roger
The answer is to buy parts from an MB dealer.
Then you will be spared these parts fiascos which can fail or not be to spec (as you have discovered) and do serious damage to your van.
Junk is expensive at any price remember.
Dennis

Click to expand...

I hear ya. A couple of years back i bought pattern part bulb holders (knowingly to save money) for the back lights and had no end of electrical problems (think DJ's disco lights whenever you switched them on) switched out to OEM parts and everything was fine, was definitely a case of buy cheap buy twice.

Gonna head over to my local MB truck counter later in the week & get the hoses.

Thanks for looking in.

Roger,

This is the eBay store for my local MB dealer, Midland Truck and Van (formerly Gerard Mann)...

https://www.ebay.co.uk/usr/mtvparts

All the parts listed will be genuine MB.

Keith.