Engine water temp stuck @ 70 degrees / thermostat cool/normal stat

[_Matt_ 26]

Hi,

 

I went for a long run at the weekend around the motorway. After getting stuck in some traffic and seeing my engine temp rise from 85 to 90 I noticed it sank down to 70 once on the move again. It rose again to 85 a few times on the remainder of the journey but spent most of it's time @ 70 degrees.

 

The previous owner said the thermostat was a cool stat from the VR6 used in the T4 camper van. I assumed 85 was the cool stat normal position.

 

I know the dial isn't that accurate but I'm thinking my stat is starting to get stuck open if the reading is sitting at 70 and I need to think about replacing it? Oil temp remained as it usually does: 100-106 on a motorway cruise. I don't know when it was last done but can see the main rad hose to the right of the engine was replaced in 2011 so guessing it was back then.

 

So assuming I need a new stat (and housing as I'm lead to believe from reading around) should I go for a normal stat or stick with the cool stat - what's the benefit/why bother with the cool stat - is it just less stressful sitting in traffic jams knowing the temp is unlikely to go over?

 

Cheers

Matt

[swiftkid 1]

Personally, I'd get rid of the low temp thermostat, yes it will make your car run cooler but if everything is working as it should it shouldn't get too hot anyway and even if it does get a little hot, that's what the 3 stage fan is for.

You will find that the low temp thermostat's will keep the engine temp around the crossover point of closed/open loop so you'll end up using more fuel as well.

 

Don't think you'll need a new housing, should just be able to swap thermostat

[_Matt_ 26]

Cheers yeah I’ll stick it back to the original spec stat. is it an involved job? Ie drain coolant and lots of taking stuff off to access? I’m coming back to working on cars from a 15 year break so confidence is lacking and I’ll use my mechanic if it’s complicated.

[Jon_vr6 1]

Yeah bin the low temp stat mate ran one for a while but didn't see any benefit.

 

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[swiftkid 1]

Nah its easy, will probably only take half an hour. Remove the 3 Allen head bolts from side of thermostat housing and gently slide it off the crack pipe, be very careful with the crack pipe as it does have a tendency to Erm... Crack.

You can drain the water by removing the bottom rad hose.

 

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[_Matt_ 26]

Cheers, that sounds ok. Watched for a few youtube vids too. This seems the best time as any to get my sleeves rolled up.

 

Await further threads on - feck I cracked the the crack pipe what now or how do I get an air lock out :)

[Roger Blassberg 0]

Be aware that all those plastic parts will be very brittle if they are the originals. Get a set of replacement rubber o-rings at the very least because if you reuse the old ones they WILL leak.

 

best of luck,

 

RB

[_Matt_ 26]

Thanks Roger. I'm tempted buy all the bits - crack, termo housing & rings. If anyone has part numbers or recommended suppliers that would be great.

 

The crack housing concerns me a bit as I gather you have to push it through the (head?) and have to feel your way to making it connect on the other side. Need to do some more research here, only saw one video on this part's replacement and it was on an R32.

[Roger Blassberg 0]

All the part numbers are in the list given in the Knowledge Base/Engine/ Timing Chain Replacement Part 2, sub-forum. Sadly, the prices quoted are out of date and some parts may be obsolete from VAG but still obtainable via eBay or from VW Heritage.

 

Best wishes

 

RB

[swiftkid 1]

I think you can get all the replacement parts from avs.

Its pretty much the same as the r32, just the r32 crack pipe is a fraction longer. nothing is internal, it's all accessible.

 

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[fendervg 30]

Are you basing your temperature readings off the dash gauge? In my experience that reading can vary wildly and is really only helpful as an indication of when you should pull over and stop to avoid overheating!

 

You could try hooking up VCDS diagnostics software - this will let you see the exact coolant temperature that is being reported back to the ECU by the blue temp sensor. Alternatively, swap the plugs around between the blue sender and the (yellow, I think) one for the dash to see if the reading changes. All are located at the front of the thermostat housing.

 

I used to run the low temp rad switch mentioned in the "Definitive VR6 Cooling" thread on here for a few years, but replaced it with a normal one once it went faulty. Having refurbished/replaced most of the cooling system I didn't have any issues - I think most of the over heatng happens when there is already a problematic component somewhere in there such as a pump, rad, fan, stat etc., and the low temp alternative parts are fitted in an effort to fix this and end up masking the real cause.