ALH Jetta VERY long to pick up heat, thermostat tested good.

Hello!

I'm pretty sure this problem wasn't there last year.

Lately, I've been experiencing this problem a couple times as temperature is starting to go down.

Today, it was about 32-34 F outside. Started my trip with a cold engine.
Took exactly 30 miles (50km) of mostly high speed (50-60mph) to get to it's full operating temperature which is around 87C (about 190F on Scangauge II). I tought it was a pretty long way to get to temps compared to what I remember from last year.

Also, while coasting down a small hill or relasing go pedal for several seconds, I can see my temperature go down a lot, I saw it go down to as much as 75C ( about 167F ) .

Around here, temperature are frequently bellow 0F, down to about -22 in worst scenarios so I'm a bit worried as to whether I'll have heat in the cabin during winter time or not.

Most or my trips are about 10 miles and I remember getting to temp just when I was arriving at destination and it was way colder outside and I was traveling at much slower speeds. So I'm pretty sure I'm having an issue.

Yes, during winter nights I'm using a frostheater and I also use a blocked-off grill. (Should start using them soon) But while at work, I have no way to plug car and never got an issue starting it daytime when temperature is usually a bit ''hotter''.

I've checked my thermostat (which is about 2 months old) using the cooking pot technique, with a thermometer in the water, and It prooved good. Also put back my old thermostat in the car and same results happened.

Are there any other reasons that could lead to a colder than usual engine or causing an engine to cool too much?

Mucho thanks for the help!

G.b.

Seems like it’s over cooling? Did any of the ears on the thermostat housing break off & get stuck in the thermostat itself, which causes the thermostat to stay open (over cooling) happened to me


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''Are there any other reasons that could lead to a colder than usual engine or causing an engine to cool too much?''
Have you replaced your coolant temperature sensor lately?
A faulty one may or may not throw a code and report incorrect temp to the ECU. Of course that wouldn't effect the Thermo.....hmm. Just thinking out loud.
Also, is your coolant properly thinned out (50/50) with distilled water?

1) Are you running the cabin heater fan/blower on a speed higher than 1 or 2 until it reaches normal 87?? The heater core is the primary heat exchanger (full coolant flow thru it all the time) and the blower fan at high(er) speeds is very effective at reducing coolant temps.
2) At less than about 60 mph you aren't working the engine much and will take longer to warm up.
3) Cooling fan(s) running when cold??

After seeing where your thermostat opens (cooling), Check at what point the thermostat CLOSES, if it closes late, you won't build up heat.

Thermostat housing has been changed with the thermostat, everything went well and I do not think any of the ears broke off. I also changed the cooling sensor at the same time as the thermostat.

Coolant is about 3-4 years old. OEM g12 or g13 (Can't remember) used with distilled water.

I think the cabin heater/fan may have been blowing full speed while driving, I've always done this, otherwise, if I wait for the engine to be full temp, I can't even get a tiny bit of heat before arriving at destination (work) everyday.

Cooling fans are not running when cold. I've checked, they start at about 95-96.

I'll have to check at what point the thermostat closes, I had never tought about that, nor did I ever tested this. Is there any specification for this?

Thanks for help ppl, not looking forward freezing this winter.

G.b.

Running cabin blower fan on high before getting up to at least mid-range normal operating temp will cause very long (if ever) full warm ups in cold weather short trips. Heated seats help SO much...
I don't think I've ever ran the fan on HI, even in summer cooling. Never needed to in cold weather, either. Unless you work the engine a bit more aggressively than I do, high speed on the blower fan will drop operating temp and result in lower cabin heat output. At least in my cold weather experience.

Is your EGR deleted?

EGR present, not clogged, everything stock.

I noticed today on my scanguauge that the engine has no problem to reach 60C. Then, getting to 70C is a lot longer... and 87... like... forever.

I will try not to use the fan for the first part of my commute to note the difference.

I LOVE the heated seats, but I find mine pretty slow to heat up my ass, I've tried more recent cars which were faster but mine must take 5 minutes for me to even feel the heat, then 10 minutes total to get full temps... usually I get heat from the seat not long before I get heat from the engine...

Again, I'll try beeing less agressive with the blower fan!

What's the temp rating on your Tstat?
I've noticed there are several aftermarket with widely varying ratings.
70C is about 160F. Thats the lowest I saw, I just bought one rated for 195F ~90C
EDIT: Stant 45379, ebay item# REDACTED LOL
(I got mine at a carQuest for a buck more -will install it when I get a chance):

heh, didn't reach tstat temperature at all on the way home from work today.
Got a few EGR coolers saved up, gonna put them in place of the atmospheric turbo. Get at least some coolant heat.

guillaumeber said:

EGR present, not clogged, everything stock.

I noticed today on my scanguauge that the engine has no problem to reach 60C. Then, getting to 70C is a lot longer... and 87... like... forever.

I will try not to use the fan for the first part of my commute to note the difference.

I LOVE the heated seats, but I find mine pretty slow to heat up my ass, I've tried more recent cars which were faster but mine must take 5 minutes for me to even feel the heat, then 10 minutes total to get full temps... usually I get heat from the seat not long before I get heat from the engine...

Again, I'll try beeing less agressive with the blower fan!

Click to expand...

The heated seats in my '01 (w/cloth seats) heat up really fast and HOT, even on "3" setting, the '03 (w/"leather") seats heat up slow and almost unnoticeable until "4-5".
The '01 is my "winter driver" but mostly for other reasons.

I have a ‘spare’ almost new non OEM thermostat sitting on a shelf. Cost half or maybe less than half of what the one I bought from the dealer to replace it cost. Pain in the butt to change too.

Without the EGR cooler the BEW still gets to over 80C in 15 km on a level road at near freezing ambient. Still won’t stay at temperature driving 100 km/hr when it’s below -10C though. Cabin heat isn’t a problem in either case.

From memory, (I believe I posted it somewhere previously, but good luck finding it) mine closed in the 160ish range opened 190ish.
I also flushed the heater core back and forth alternating air and water until clear. By your posted operating temp, a heater core is not your issue though. Just throwing that out there, in the 70's we did that as part of a low cabin heat service.
Both our ALH's heat up quickly while driving, cabin heat starts by the time I reach pavement, 3/8 of a mile, full operating temp usually within 2 or 3 miles.

We see this every fall. Since you have a scan gauge that helps. When the weather gets cold your diesel takes longer to heat up. If you observe your scan gauge and your heat gauge you will notice that the heat gauge starts to move at 124* it reaches straight up at 164*.

At that point it looks like your car is up to temperature according to the heat gauge but it is still 26* below the correct operating temperature. The colder it is the longer it takes to reach the 190* mark. A winter front or grill blocking helps but driving under load is what really makes a difference.

I have one place I frequent that is on a hill, occasionally on a very cold evening I will start for home and it’s all downhill for the first 3 miles, my cars needle on the dash hardly moves, sometimes it doesn’t till I get to flat ground and put some load on the engine. I have an ultragauge and the actual temperature is sometimes less than 124* all the way to the bottom of that hill.

If your temperature is not reaching the 190* mark in a reasonable amount of time, I would replace your thermostat, they can get weak over time. A word of caution, thermostats can be cheap you might be able to find one for less than $10, don’t , idparts has an oem thermostat, I would check your suppliers on that side of the border maybe even a dealer for an oem thermostat.

If it is reaching 190* or at least in the 180’s in say a 10 mile drive (not downhill) on a chilly 32* (0c) day then I’d say you’re close to normal.

I drive almost exactly 10 miles to work, only on the coldest of days 0F or below am I still not up to the 190* mark.

Replace the thermostat with a good OEM one. problem will be solved

If you want to test the thermostat in car, pinch a rad hose completely shut and see how long it takes to get up to temp. Obviously only do this if you are paying attention and will be travelling where it is safe to pull over once you get up to temp to remove the clamp.

This seems pretty simple. Despite your test, it's clear from the car's behavior that the thermostat isn't working properly. Replace it and I bet things will be back to normal.

I might be trying a new OEM thermostat then...

However, I would like to try the ''pinch the radiator hose'' trick before, just to compare.

Actually, how does one manage to pinch a radiator hose without damaging it, without any special tools? Are there any common tricks?

I'm having difficulty blaming the thermostat because I know it's closing when cold, and also, the problem happens even BEFORE the Tstat even comes into play... before it even opens for the first time...

I can't imagine the Tstat beeing 100% closed when I removed it and trying it in my hot water pan on my stove, but staying open when put back in the car.

Thanks all for the help!

Thermostat design is a big factor, you probably need to get a higher temperature thermostat. I found if you get one without holes in it letting coolant flow just a little, they was up much faster. Usually the higher temp ones don't have holes.

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Diesels are bypass systems. Trust me on this -- the OEM thermostats are worth the money in this application while the cheaper, aftermarket ones -- often not so much.

They have tools at Harbor Freight to pinch hoses.

2 pieces of wood/steel on each side of the hose pinched together using vise grips or a c-clamp will do the trick. You'll probably need a helper though. Make sure it's pinched right off or the test won't be accurate.

Looking at another post about the temp sensor I saw the coolant glow plugs. This is something we rarely ever think about, seems as if it should throw a code, however, new coolant glow plugs might just help good pic of coolant temp sensor also.
http://forums.tdiclub.com/showpost.php?p=838469&postcount=2

coolant glow plugs are not on before the engine is running
besides, they do not even make a huge difference in warmup when factory-switched, let alone getting heat into the piston bowls before cranking

They shut off after a couple minutes regardless of temp (same time as when the high idle shuts off). You can ground the relays with a switch in the cab to keep them on, but as said, they don't really put a huge amount of heat in there, iirc around 1000 watts when all three are going.

The ECU doesn't monitor if the coolant GPs are working or not.

[486] said:

coolant glow plugs are not on before the engine is running
besides, they do not even make a huge difference in warmup when factory-switched, let alone getting heat into the piston bowls before cranking

They shut off after a couple minutes regardless of temp (same time as when the high idle shuts off). You can ground the relays with a switch in the cab to keep them on, but as said, they don't really put a huge amount of heat in there, iirc around 1000 watts when all three are going.

Click to expand...

It does make a difference though and possibly more on short drive situations mentioned.

jettawreck said:

The ECU doesn't monitor if the coolant GPs are working or not.

Click to expand...

I was wondering about that

Pinch radiator hose, just squeeze it with your gloved hand, if it seems like that would damage it, the hose is shot.
Issue sure sounds like thermostat, but 2 months old seems it would be a pretty raunchy part (ebay, amazon).
30 minutes highway speed to get to temperature is a problem, if not thermostat, failing water pump, clog, low coolant or leak. Guess you'd also want to rule out errant sensor reading.

Sensor has been changed at the same time as the thermostat... 2 months ago, max.
Sensor seems right as it finally gets to it's working temperature... EVENTUALLY.

After 30mins +, i finally get to about 91C and it seems to stay there, as long as i keep load on the enigne, otherwise, it will drop down some degrees.

I have now installed my blocked-off winter grill and bocked the lower bumper grill too. Doesn't seem to do much difference.

I will really need to try to pinch a radiator hose, was supposed to do this this week-end but I will have to deal with my sticky handbrake cable/caliper... which started acting since cold weather arrived...

This car makes me work every damn weekend... !

Replace the thermostat with a good OEM one. problem will be solved.