Dodgy thermostat

[Vitwagen]

Hey Guys,

I'm wondering, can thermostats be sticky/not open fully?

My truck, with near standard AAZ, has perfect temps all the time, until you get the speed up. after 60 MPH, the oil and water temps rise fast and keep rising, with EGTs around 400Degs C.

As soon as I slow down, the temp drops.


is it possible that the thermostat isn't opening properly, and causing a restriction? it does seem pretty slow to react to changes in engine temp.

HALP! 

[R.O.R-2.0]

either that, or possibly a crack in the head..

[Vitwagen]

either that, or possibly a crack in the head..

Christ, don't say that! I've only just replaced it 

The coolant level and pressures are spot on. no loss of coolant. nothing irregular except this temp thing...

 

[R.O.R-2.0]

take the thermostat out, and boil it, see what temp it opens at, and if it opens completely..

[Vitwagen]

Hmm, did that, it opens slowly, but how do I know if it's open fully? not much really happened TBH, just the rubber on the shaft moved.


And who thought it a good idea to put the thermostat on the BOTTOM of the engine? 

[R.O.R-2.0]

Hmm, did that, it opens slowly, but how do I know if it's open fully? not much really happened TBH, just the rubber on the shaft moved.


And who thought it a good idea to put the thermostat on the BOTTOM of the engine? 

doesnt matter its location.. ive seen them everywhere.. hell, the one on my toyota is on the front of the engine, sitting on edge..
my audi 5kTD, same deal, t-stat is on edge, in the side of the block..

the hot water from the top of the engine is still getting circulated over the thermostat. sure, heat rises, but heat also falls when its pumped to a lower spot.. apparently the VW engineers thought it was a good idea to put it down there.. and ive seen nothing to suggest it was in a bad spot..

heres a better question:

WHO IN THEIR RIGHT MIND PUT THE ALTERNATORS ON THE BACK SIDE OF A HONDA ENGINE?! you cant even see it, let alone get at it easy to replace it.. same deal with their oil filters.. on the back! wtf?

[Vincent Waldon]

They are cheap, they fail regularly, they are a pain to remove and install... me personally: I just install a new one and be done with it.  Your symptoms certainly sound t-stat related, and Occam's Razor says the simplest answer to a question is usually the right solution. 

If your t-stat housing is plastic it's a good idea to replace it as well... it's even cheaper and loves to warp.  Unbolt it and it will spring into a new shape and never seal properly again. BTDT.. twice. 

[R.O.R-2.0]

They are cheap, they fail regularly, they are a pain to remove and install... me personally: I just install a new one and be done with it.  Your symptoms certainly sound t-stat related, and Occam's Razor says the simplest answer to a question is usually the right solution.  

If your t-stat housing is plastic it's a good idea to replace it as well... it's even cheaper and loves to warp.  Unbolt it and it will spring into a new shape and never seal properly again. BTDT.. twice.  

there only hard to replace if you have a/c and power steering..

on all my cars, it takes me like 15 minutes to remove, and re-install a thermostat. oh, the beauties of cars with nothing on them besides an alternator <3

(also, be sure to buy a GOOD QUALITY (should cost about 20 bucks) thermostat.. the cheap, stamped steel ones are pretty much junk. ive seen a high failure rate with brand new cheap thermostats.. like over half of the cheapo's are junk, right out of the box. from my experience atleast)

[Vitwagen]

Awesome, thanks guys.

It is indeed a newish-looking stamped tin jobbie. I just took the truck for a spin, 20 mins at 30-50 MPH, my digital temp gauge (sensor just after the head) never got above 70 degs C.

Oh, the only reason I think it's daft having it there is beacuse it means having to drain the whole system in order to fit a new one! 

[R.O.R-2.0]

gives you a good reason to inspect your coolant tho..

the coolant still looked purple in my rabbit, but upon draining it, it wasnt purple/blue anymore.. it was BLACK.

and if you have an aluminum water neck, then you can drill and tap it in the corner, and voila, instant drain plug!

[NA diesel]

gives you a good reason to inspect your coolant tho..

the coolant still looked purple in my rabbit, but upon draining it, it wasnt purple/blue anymore.. it was BLACK.

and if you have an aluminum water neck, then you can drill and tap it in the corner, and voila, instant drain plug!

Have a part # or application (vehicle on which it is original equipment) for the aluminum t-stat housing?

[Vincent Waldon]

A1s and very early A2s... if you want one keep your eyes peeled at the local wreckers since they are NLA from VW.   

[R.O.R-2.0]

gives you a good reason to inspect your coolant tho..

the coolant still looked purple in my rabbit, but upon draining it, it wasnt purple/blue anymore.. it was BLACK.

and if you have an aluminum water neck, then you can drill and tap it in the corner, and voila, instant drain plug!

Have a part # or application (vehicle on which it is original equipment) for the aluminum t-stat housing?

all mk1s had aluminum water necks. for the heater hose connection, and both radiator hose connections..

i believe even the gas mk1s had the aluminum parts.

my 85 GTI even had aluminum water necks, but my 86, had plastic originally, but now swapped to AL-13..

[R.O.R-2.0]

A1s and very early A2s... if you want one keep your eyes peeled at the local wreckers since they are NLA from VW.   

lol, i love how often times we have almost identical responses.. yours was just worded much better..

[8v-of-fury]

Pretty sure both my 91 na and 91 td both have aluminum thermo housings as well.. Seems a lot of vw stuff is inconclusive. Lmao