engine slow to warmup 92 Ecodiesel

[92EcoDiesel Jetta]

I drove 10 miles from a cold start at ambient of 50 F and the engine did not fully warm up. It used to be up to temp by 4 to 5 miles with good heat by then.

Upper radiator hose was hot (160F per ir thermometer), lower rad hose was cold (per my fingers and 72F per ir thermometer). heater hoses in/out the fire wall were hot. I was getting coolant flow in the expansion globe.

What do you think is wrong? T stat was new 3 years ago (192F) as well as new water pump.

[Hoble]

my guess is the same as whats going on in this topic
http://www.vwdiesel.net/forum/index.php?topic=32436.0
it explains everything

[CrazyAndy]

If you want to test the thermostat in your car, you could do what us air cooled guys do and put your thermostat in a bag (or not since it IS a water cooled T-stat) and submerge it in partially boiling water; if it opens fully then it's just the cold northern NY temps getting to your car and consider doing what they do in that other thread.  Hope that helps!

[92EcoDiesel Jetta]

Would a stuck open thermostat cause the lower radiator hose to be cold? Or only a blocked radiator?

[TylerDurden]

It's a tricky question...

A good radiator can be absurdly efficient at cooling. I could see a >50F drop in coolant temp from the inlet to the outlet, when the t-stat was fully open. If the t-stat were stuck part-way, only a part of the flow would circulate through the radiator and might allow greater cooling.

Is the A/C condenser still in place?

[Gizmoman]

50 F is not that cold (some here would say it's warm) My 1st guess is a stuck closed T-stat. Can you feel or hear coolant flow (using a long screwdriver from the top rad hose connector to your ear). The warm upper hose is probably just heat transfer of the coolant as heat rises, even in fluid. Here's a link to a typical diagram-
http://www.peachparts.com/shopforum/attachments/diesel-discussion/47719d1189368702-coolant-flow-path-82-300tdt-coolant-flow-diagram1.jpg - not our engine but the same principal.

Other things to check would be the plugged radiator as you mentioned or a loose pump impeller (don't know if that can really happen though). I'm no expert but these are things I'd look for and in that order.

Good luck

[92EcoDiesel Jetta]

AC condenser in place. Coolant level is full. Fan is not running constantly.

Something definitely changed in the past few weeks where it would take longer to warm up and less heat output from the heater. If the thermostat is stuck shut, how long will it take before the engine overheats at 50F ambient driving around not stuck in traffic?  I have the stamped metal impeller water pump. If the impeller is slipping, would that cause the lower rad hose to be cold and less heat output?

[TylerDurden]

Stuck closed will show normal warmup and cabin heat, until it overheats. Stuck open will delay warmup and lower cabin heat.

Does the gauge read lower than before?

Overheating takes a good while in cool flatland operation.

Three years is not a bad interval to change the t-stat (still a PITA if u have PS). T-stat housing (elbow) should also be replaced. I'd test the new t-stat before installation.

(Using a vacuum cleaner to keep the new tstat in place while installing the o-ring and elbow works a treat.)

[Hoble]

In the last few weeks has the outside temp been getting cooler? Did you have this car last winter too?

[Gizmoman]

No idea how long it would take but as has been mentioned, these engines are big heat sinks and if it's really really cold - may never warm up.
OTOH, overheating one is a very expensive moment.

You eventually need coolant flow at 50 F ambient unless you never drive more than ten miles. Some of the folks to the North may seldom have theirs open at all (or only slightly) in the winter.

The Bentley basically says a stuck open stat will make both hoses warm but the engine will never reach full temp. A stuck closed one (or a plugged rad) will leave the lower cold. It makes no mention of checking the impeller - it's only a possibility but certainly not at the top of the list.

Again, overheating one is very sad thing and you don't want to go there. Don't mean to be a jerk but three years has little to do with the device going bad - it could happen on day 2 - I'd pull it and drop it in a pan of boiling water.

[92EcoDiesel Jetta]

In the last few weeks has the outside temp been getting cooler? Did you have this car last winter too?

I've had this car for 3 winters now and I've always marveled at how fast and how much heat I get out of this beast so something is definitely not right.

[R.O.R-2.0]

In the last few weeks has the outside temp been getting cooler? Did you have this car last winter too?

I've had this car for 3 winters now and I've always marveled at how fast and how much heat I get out of this beast so something is definitely not right.

usually its a funky T-stat..

[8v-of-fury]

10 Miles seems like it should be enough time to heat up. I am pretty sure in part of my drive from work to the highway which equals ~10miles I just get the car up to about 3/8 on the gauge. This is from a similar temperature cold start, and the top of 4th gear for the duration.

HOWEVER i encounter a lot of hills and winding roads like you would see in mountain passes. Not that I am in the mountains but the Canadian Shield proves a challenge when designing a roads path.

I have three diesels in my driveway right now to be subjective to this; a 1.6 TD a 1.9 AAZ and a 1.9 M-TDI. Out of them all the 1.9 AAZ gets heat the fastest while idling, the 1.6 TD will get up to temps the quickest from driving, and the 1.9 M-TDI doesn't make heat ever.. Lmao.

Depending on what temperature thermostat you have in the engine it really decides how it will react in the cold weather. If you have a 195 thermostat, it should theoretically almost never open in the winter. My 180 barely opens when driving around for ever.

[92EcoDiesel Jetta]

I drove the car again and it seems to warm up normally this last time so it was an intermittent problem. Maybe the T- stat is funky.

I didn't drive it that long or far this time, about one mile at 30 mph on flat roads, then idled it and watched the gauge and felt the hoses, shot it with the IR thermometer. Progressively got good normal heat while it idled. The gauge eventually reached the middle mark after 10 -15 minutes of idling. All the hoses got hot except the lower rad hose. The radiator felt colder the lower I felt. The lower rad hose was warmer at the rad neck end than at the T- stat end, which indicates coolant was flowing at a very slow rate. Everything was normal IMO. I will keep monitoring.