2.4DW in VW LT - Overheating on short runs - no load

[blix99]

Hello.
I've just got my newly aquired VW LT camper on the road after over 4 years sat idle.
I spent a lot of time trying to get the engine to run OK (IP pump seal and timing, new injectors, new injector hoses etc)

It used to be awful to start, rough idle and lots of smoke. All seemed well and it starts really easily now, even if sat for a couple of months. It idles well and doesn't smoke.

However, late last week was the first time I could actually drive it and it seems to overheat.

This is on short jourenys with no real load, maybe a mile or so, once it's up to temp and all pretty flat driving. My temp gauge is just a needle with a red led in the middle. It has a 'box' at either end of the 'range'. One for low temp and one for high. When up to temp, it sits just below the high temp box and the LED flashes on occasion.

What I mean is, it's maybe 1/4 of the way past the central mark all the time whnen driving but the overheat light flashes seemingly quite randomly then goes out then will come on again. This doesn't seem to happen during high revs or hilly sections of road. I can't really see any pattern to when or why it flashes when it does?

I've checked the coolant. Level is good and it seems to circulate OK.
I've checked the rad for cold spots and this seems OK too. I've removed it and flushed it and it actually seems in good condition.
All pipes are OK. No leaks.
I've changed the thermostat. I was convinced this would be the issue but it's not solved it. However, I read this thread:
https://www.d24t.com/showthread.php?...ht=overheating
partucularly this comment by V8Volvo:

You may want to STOP for a moment and make sure this is right before you put it back together. Can you post a picture of the thermostat and gasket you bought, or post the part number from the box?

Remember this thermostat is an AUDI part and Volvo plays no role in manufacturing or engineering it. Even the tstats sold by the Volvo dealer are repackaged VW/Audi parts.
You probably received a thermostat and gasket by mistake that is for a GASOLINE Volvo engine since those do use a grooved gasket that goes around the perimeter of the thermostat. In that case not only is the gasket wrong but the thermostat may be wrong also. If the thermostat is for the wrong temperature or doesn't function the right way, have the correct block-off dimensions, etc, it will cause serious problems.

The friend you spoke to is wrong, the thermostat gasket for the DIESEL engines never has changed and continues to use an o-ring that sits outboard of the thermostat. The GAS engines do now use the style you described. Your friend might not have been aware that the gas and diesel engines in these cars have no parts or designs in common.

Rather than trying to make something work with sealant you should ensure you have the correct parts. Can you give us more info on the thermostat you have?

Don't run the car with this thermostat in it until you have confirmed that it is correct.

The thermostate I bought had a gasket that fitted around the rim of the stat and wouldn't fit within the housing opening. However, the old stat had an odd gasket too but it did fit above the rim. I'm now wondering if the old one and the new one are wrong?
Would this cause overheating?

My other thoughts are:
Condition of the water pump. Is there a way to check without dismantleing everything? It's definitely pumping but maybe not enough?
Oil. I need to do an oil change but I've never had any overheating problems for older oil. Level is good.
Timing - cam and IP - The fact it starts OK and seems to run so well, I'm thinkning this is unlikely but I don't know? Could something here cause a problem?
That it's actually running at OK temp but the reading is wrong? Sender or gauge?
Blocked waterways on the case / head? Again, how would I know?

Does anyone have any ideas of my best course of action as i can't go anywhere really for fear of a seize or cracking the head.

Thanks in advance for any input

[v8volvo]

Based on what you wrote, and on the other good work you have already done, I think your suspicions about the thermostat possibly being the wrong part are worth investigating further.

The correct type thermostat for this engine is a simple one with a block-off plate for the engine's internal bypass return (when the tstat is open). It does not use a gasket around the perimeter of the thermostat flange; rather, it just has a simple O-ring that goes on the outside of the tstat.

Can you post a picture or part number of the thermostat you installed, or its box? What brand? And what temperature rating? For the correct type tstat, there are several tempeature ratings available, the common ones being 80C and 87C. The 80C version has proved to be the best choice for promoting stable engine temperatures especially in vehicles that are subjected to hard work.

I would start by making sure this area is right, then move on to other possibilities after confirming it.

Here is what the correct thermostat looks like, as sold by Brickwerks there in UK. Does yours look like this? https://www.brickwerks.co.uk/lt-part...2-4d-80-c.html

Here is another view of it, below, showing the back (towards engine) side of the thermostat and the circular block-off plate it incorporates. Did the tstat you installed have this plate? Many other thermostats do not. If a thermostat is installed that fits in the main opening but lacks this plate, the result will be that the water pump is continually pulling coolant through the internal bypass, rather than the radiator, meaning the engine's cooling capacity is greatly reduced.



Let us know what you find -- it is probably something simple if it overheats this quickly. And you are certainly right to not want to drive it at all until it's able to stay cool.

[blix99]

Hey. Thanks very much for the reply and the link / photo.

I had seen the Brickwerks unit and understand that the 80deg one is better than the 87 deg standard unit. However, all this was gleened after I bought and replaced the current tstat (typical, eh!!)

So, this is the one I took out. It doesn't seem to have a part number but is 'Wahler - West Germany' It also has '87' stamped on the bottom as well as '4/3' (not sure what that might signify?)





I didn't take a photo of the one i put back in but this is the box. It came from a motor factor online who ask for all vehicle details before showing products. The only discernable different was the seal fitting around the rim rather than on top of it afterwards.



I did test the original tstat I took out in a pan of boiling water and it did seem to work so I'm still unsure if this was the probelm anyway??

[ngoma]

Couple more thoughts:

Did it do this before? What was the temp. gauge behavior before the layup?

Just to be sure the temp. gauge is not lying to you, verify the actual temps with an IR laser thermometer.

We are not as familiar with the cooling system topography (outside of the engine itself) in the LT; might there be an air bubble trapped somewhere?

[ngoma]

That T-stat appears to be the correct one. We don't see them with the bleeder orifice (should be oriented at the 12 o'clock position) and it is not really useful in our application. Did the new T-stat have one?

Probably the encircling seal instead of the simple o-ring is OK as long as it seals sufficiently well inside the housing. Disc to be installed facing toward the engine block, ya?

The 87 imprint is, of course, the temperature rating. I don't know what the other number is. The one I am looking at currently (much newer, as it says "Made in Germany" vice yours "Made in W. Germany") has a "07 09" stamping opposite the temperature rating.

Good on you for testing the old one-- keep it as a spare.

If you like we can compare dimensional measurements: disc diameters, and disc to disc height.

There have been some isolated reports of defective water pumps. Not so much corroded impellers, but impellers slipping. As you imagined, there is no easy/painless way to verify this. I guess just to continue systematically verifying all the other factors are in good working order.

ALSO: Brickwerx lists the WP version that has less cog teeth. You may ultimately want this for its theoretically increased output for a given engine speed.

[ngoma]

Here are the correct T-stat dimensions. Use Typ 4116 for the A dimension (67mm):



I have verified these dimensions with my caliper and correct T-stat.

[blix99]

Hello.
Thanks for all your replies and help.

So, I removed the new tstat that I fitted and checked that, along with the old one. Both seem to work OK but the new one opens more.

Also, the new one has a smaller disc on the bottom , approx 35mm diam.

However, all of this is academic as neither solve my overheasting problem.

I foolishly only checked the rad was OK and got hot when I removed it and flushed it through. I did this with boiling water and checked that the rad got hot in all areas, which it did.

So, I've now checked it when the van is running hot, in situ (which obviously i should have already done. D'oh!) and it is cold, as is the bottom exit pipe.

So, the coolant is not being circulated around the rad at all.
Having removed the rad and inspected it, I'm pretty confident that this is OK and not blocked.

When the system is full, I can squeeze the hose which enters the tstat housing, which comes from the bottom of the rad, and the coolant in the reservior is affected via the top pipe into the reservior from the top of the rad, so coolant is able to move around.

So, my thought now is the water pump not circualting. I had thought it was circualting due to noticable movement in the reservior but this this is proabbly more likely just movement from the initial difference in water temperature.

Does this sound resonable?
Anything i might be missing?

I think I'll change the pump anyway and do the timing belt at the same time; something that is on my list anyway, for my own piece of mind. Hopefully this will sort it out. If not, I'm stumped??

[ngoma]

Minimum allowable T-stat opening is 8mm (fully opened).

Did you follow the steps to purge entrapped air when you refilled?

In the Volvo, that entails disconnecting the small upper hose from the the cold start waxstat, holding it level with the expansion tank, and verifying no more air bubbles are exiting.

As an experiment, you should be able to do this with the engine running, and by revving up the engine, see increased flow correlating to the engine speed. Have a helper refilling the expansion tank so it doesn't run dry. This would tell us that you have at least some functionality from the WP.

Normally the lower portion of the radiator will be cooler, but it shouldn't be cold, especially when the engine has been operating for some time under load. Did yours stay cold even after driving it (more than 10 minutes)?

Did you verify the gauge indications with an IR thermometer? You can aim it at the engine block next to the temp. sensor, at the radiator hoses, at the radiator tanks (upper and lower sections), at the radiator hose flanges, and take notes.

REMEMBER, IDI diesel engines do not come up to operating temperature as easily as gassers, when started from cold and simply idled. They require a load.

[jpliddy]

Originally Posted by blix99

Hello.
I've just got my newly aquired VW LT camper on the road after over 4 years sat idle.
I spent a lot of time trying to get the engine to run OK (IP pump seal and timing, new injectors, new injector hoses etc)

It used to be awful to start, rough idle and lots of smoke. All seemed well and it starts really easily now, even if sat for a couple of months. It idles well and doesn't smoke.

However, late last week was the first time I could actually drive it and it seems to overheat.

This is on short jourenys with no real load, maybe a mile or so, once it's up to temp and all pretty flat driving. My temp gauge is just a needle with a red led in the middle. It has a 'box' at either end of the 'range'. One for low temp and one for high. When up to temp, it sits just below the high temp box and the LED flashes on occasion.

What I mean is, it's maybe 1/4 of the way past the central mark all the time whnen driving but the overheat light flashes seemingly quite randomly then goes out then will come on again. This doesn't seem to happen during high revs or hilly sections of road. I can't really see any pattern to when or why it flashes when it does?

I've checked the coolant. Level is good and it seems to circulate OK.
I've checked the rad for cold spots and this seems OK too. I've removed it and flushed it and it actually seems in good condition.
All pipes are OK. No leaks.
I've changed the thermostat. I was convinced this would be the issue but it's not solved it. However, I read this thread:
https://www.d24t.com/showthread.php?...ht=overheating
partucularly this comment by V8Volvo:


The thermostate I bought had a gasket that fitted around the rim of the stat and wouldn't fit within the housing opening. However, the old stat had an odd gasket too but it did fit above the rim. I'm now wondering if the old one and the new one are wrong?
Would this cause overheating?

My other thoughts are:
Condition of the water pump. Is there a way to check without dismantleing everything? It's definitely pumping but maybe not enough?
Oil. I need to do an oil change but I've never had any overheating problems for older oil. Level is good.
Timing - cam and IP - The fact it starts OK and seems to run so well, I'm thinkning this is unlikely but I don't know? Could something here cause a problem?
That it's actually running at OK temp but the reading is wrong? Sender or gauge?
Blocked waterways on the case / head? Again, how would I know?

Does anyone have any ideas of my best course of action as i can't go anywhere really for fear of a seize or cracking the head.

Thanks in advance for any input

hi
my volvo main dealer sold me a T stat with a gasket that fitted round the edge of the stat few years back they swopped it for correct one as shown in photos
but it was a pain as being volvo you think it must fit but it surely does not .

[v8volvo]

Originally Posted by blix99

So, the coolant is not being circulated around the rad at all.
Having removed the rad and inspected it, I'm pretty confident that this is OK and not blocked.

When the system is full, I can squeeze the hose which enters the tstat housing, which comes from the bottom of the rad, and the coolant in the reservior is affected via the top pipe into the reservior from the top of the rad, so coolant is able to move around.

So, my thought now is the water pump not circualting. I had thought it was circualting due to noticable movement in the reservior but this this is proabbly more likely just movement from the initial difference in water temperature.

Does this sound resonable?
Anything i might be missing?

I think I'll change the pump anyway and do the timing belt at the same time; something that is on my list anyway, for my own piece of mind. Hopefully this will sort it out. If not, I'm stumped??

Sounds like you are getting closer to pinpointing the issue.

Checking for an air pocket would definitely be the first thing, as described by ngoma above. Presence of an air bubble can prevent circulation even with a working water pump and thermostat. What is the high point in the cooling system on the LT? That is where you will want to try to burp air out.

But you're also right that it's possible for the water pump to fail in a way that could cause these symptoms. That would be in a situation where the impeller comes free from the water pump shaft, so that it is not being spun and doesn't pump fluid. This is fairly rare but not unheard of, and more common with the water pumps with plastic impellers. As the plastic ages and goes through enough hot/cold cycles it can lose its grip on the shaft and spin off.

Note that the rad will only get warm when the tstat opens so the simple fact that it is not getting warm doesn't necessarily mean coolant is not circulating inside the engine. To deduce whether the WP is working, what I would be looking at instead is the heater hoses, since (as long as the heater control valve is open and there is not a major air pocket in the system preventing circulation) those should warm up with the engine, if the WP is functioning. Did those get warm while the rad stayed cold? If so, that indicates that coolant is circulating but for some reason is not making it to the rad. But if not, that suggests no circulation -- again possible because of presence of air but also possible due to WP failure.

The more conclusive, direct test you can do to confirm the integrity of the WP impeller (without having to take the whole front of the engine apart to remove the WP) is to remove the thermostat again and look in towards the front. From the tstat opening you can see the backside of the water pump visually (might need a small mirror), and with a screwdriver or piece of bent rod, you can also reach in there and see if the impeller is loose. If you are able to spin that impeller while the engine is off, then you have found your issue.

This of course requires removing the tstat again, which you're probably tired of doing now. But if other tests or attempts to find/purge air don't get you anywhere, it might be worth a shot.