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Author Topic: Thermostat  (Read 8964 times)

November 25, 2011, 12:16:18 am

jimfoo

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Thermostat
« on: November 25, 2011, 12:16:18 am »
Was having some more minor overheating issues, so I swapped a different thermostat in my AAZ(mtdi)  It seems like I have had issues quite a lot with that. I did put a new all metal water pump in. Anyway, I tested the stat in boiling water before installing it, and it opened right where it should. Put it in, and had bad overheating! With the engine hot, the h2o pump was hot, but the rad wasn't, and I would loose heat at the heater. Can a thermostat that opens in water, not work so well when in the engine? The old one, which I had modified to block off the internal passage sooner, worked much better, but still got hot somewhat on hills, but nowhere as bad as the 2nd one. Could I have the wrong one to start with? Is an AAZ thermostat similar to any of the other engines, or is it it's own beast? Thanks!


Jim
1966 Land-Rover 88" with 1.9 1Z which has been transformed to an M-TDI
TFO35 mechanically controlled VNT, IC , and 2.5" exhaust.
Driven daily

Reply #1November 25, 2011, 12:37:55 am

CRSMP5

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Re: Thermostat
« Reply #1 on: November 25, 2011, 12:37:55 am »
boil test on a vw thermo is BAD idea... they are unsupported properly and can be damaged...

so is it a cast or stamped impeller on it?

th elittle line flowing into the bottle flowing? if nt.. ive seen them get clogged, it will trap a air pocket and cause issues..

you say aaz and tdi-m... so.. its a aaz block with tdi head/pistons? aaz=idi stock... tdi is based off aaz but different head/pistons.. just courious..

Reply #2November 25, 2011, 01:03:02 am

mystery3

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Re: Thermostat
« Reply #2 on: November 25, 2011, 01:03:02 am »
Does it overheat without a thermostat installed?

Reply #3November 25, 2011, 08:11:50 am

jimfoo

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Re: Thermostat
« Reply #3 on: November 25, 2011, 08:11:50 am »
AAZ with TDI head and pistons, brand new cast iron impeller pump. I haven't run it without the thermostat in. I don't have the "little bottle" in the conventional sense as it's in a Land Rover, but I do have a bottle that coolant can flow into and out of. Other things I have thought about are collapsing hoses as I am running Evans coolant at 0 psi. I have springs in the suction line from the rad, but am wondering about tht smaller line from the head to the WP. If that one were to be restricted, would hot water be able to reach the thermostat? Is there a complete coolant flow diagram somewhere? I have thought about making some kind of housing to put a thermostat on the hot (upper)side, but a diagram would help a lot to see if it could be done. I would have to mostly gut the lower one I think, but leave the block off plate part.
Jim
1966 Land-Rover 88" with 1.9 1Z which has been transformed to an M-TDI
TFO35 mechanically controlled VNT, IC , and 2.5" exhaust.
Driven daily

Reply #4November 25, 2011, 08:33:06 am

theman53

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Re: Thermostat
« Reply #4 on: November 25, 2011, 08:33:06 am »
I wonder if somehow air is sittiing just around your T stat. This summer when I changed coolant in the jetta it took a couple days until I quit adding coolant. It was clear full and I kept driving it, watching temp gauge, and every trip I added probably 8oz of mix. I did this for about 5 days straight. I haven't had to add since, so I am assuming air in the system. Maybe it is taking yours longer since it isn't pressurized? Just a guess to try and help, mabye start you mind thinking in other ways and actually find out what is up.

Reply #5November 25, 2011, 01:56:01 pm

CRSMP5

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Re: Thermostat
« Reply #5 on: November 25, 2011, 01:56:01 pm »
you cannot run a vw engine with NO thermostat.. its design blocks off the bypass hose.. waterpump to head... so do NOT do that.....

ok how to help...

you got the bypass hose...

how do you have the heater set up? off back of head and waterpump right?

the pipe from waterpump to heater tends to have a bottle in it.. to fill the system..

bottom of rad... top of rad...

nipple on top neck to bottle..

thats pretty much the full complete cooling system...

id add in a VW style bottle on the heater hose and nipple.. i do know for a fact that unpressurised system tends to run warmer then pressurised..

next.. rad higher then engine? if lower... how are you purging air from the head? aka vw bottle will solve that if rigged in and higher then head..

Reply #6November 25, 2011, 04:58:27 pm

jimfoo

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Re: Thermostat
« Reply #6 on: November 25, 2011, 04:58:27 pm »
Rad is higher than the engine, with the hose coming up right at the head, so air goes into rad. When bleeding, I have that side of the engine up higher and tilted so the hose side is the highest point on the head. I hope to have a good look at everything this weekend, and try a few things to see what helps and what doesn't. If I only had a crapload of thermocouples I could attach at various points, I could really understand what is happening.
Jim
1966 Land-Rover 88" with 1.9 1Z which has been transformed to an M-TDI
TFO35 mechanically controlled VNT, IC , and 2.5" exhaust.
Driven daily

Reply #7November 27, 2011, 10:03:37 pm

Toby

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Re: Thermostat
« Reply #7 on: November 27, 2011, 10:03:37 pm »
boil test on a vw thermo is BAD idea... they are unsupported properly and can be damaged...

How can heating the thermostat when it is not held by the rim be bad for it? I do this all of the time and have never had one that checked good fail in service.

Reply #8November 27, 2011, 11:07:41 pm

R.O.R-2.0

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Re: Thermostat
« Reply #8 on: November 27, 2011, 11:07:41 pm »
boil test on a vw thermo is BAD idea... they are unsupported properly and can be damaged...

How can heating the thermostat when it is not held by the rim be bad for it? I do this all of the time and have never had one that checked good fail in service.

how is boil testing a vw thermostat bad? whats the difference if the engine boil tests it, or if you boil test it in a pot of water on the stove?
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Reply #9November 28, 2011, 12:25:46 am

ORCoaster

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Re: Thermostat
« Reply #9 on: November 28, 2011, 12:25:46 am »
Maybe because it is in a pot on the stove people think they need salt in the water to make it boil better.   I heat them on the stove all the time.  Just make sure the wife is gone or there will be H to pay for using her kitchen for the garage.

Reply #10November 28, 2011, 07:28:36 pm

jimfoo

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Re: Thermostat
« Reply #10 on: November 28, 2011, 07:28:36 pm »
I put one of my modified thermostats in, and while I didn't do any long highway drives, it didn't get 250+ degrees on the first hill like it did with the old(newer) thermostat. It didn't get much above 190, though ran cooler in general. I think coolant may leak through it a tiny bit. While I had it drained, I did some measuring and found the old(newer) thermostat wouldn't close the recirc port in the water pump until it was already between 3/8-1/2" open. The modified one has a weaker spring on the plate to close the port, and I turned the plate over so it closes earlier, it has maybe a 1/8" gap before it closes the port. What is the normal gap a thermostat should have? I'm wondering if I have a different housing or the wrong thermostat. Things may be a little different also due to the more viscous coolant, but it shouldn't make that much difference.
Jim
1966 Land-Rover 88" with 1.9 1Z which has been transformed to an M-TDI
TFO35 mechanically controlled VNT, IC , and 2.5" exhaust.
Driven daily

Reply #11November 30, 2011, 08:07:04 pm

jimfoo

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Re: Thermostat
« Reply #11 on: November 30, 2011, 08:07:04 pm »
New 180F 80C thermostat, and it gets way too hot still. Radiator is cold on cold side, so causes I can think of:
Thermostat-not likely after so many tries, but modified ones do make it run cooler, so something to consider
Radiator-could be clogged, but I believe it was brand new when I got it from a friend. Worth checking
Water pump-brand new, cast iron impeller, so not slipping. Are there different sized pulleys? Could it be turning too slow?
Any other ideas?
My heaters(2) do really crank out the heat, so maybe that gives credence to the radiator theory.
Jim
1966 Land-Rover 88" with 1.9 1Z which has been transformed to an M-TDI
TFO35 mechanically controlled VNT, IC , and 2.5" exhaust.
Driven daily

Reply #12November 30, 2011, 09:43:07 pm

ORCoaster

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Re: Thermostat
« Reply #12 on: November 30, 2011, 09:43:07 pm »
Time for a hosing on the radiator I would have to agree.  Maybe it was just cleaned up when you got it and it was never cleaned inside.  Looks can be deceiving.

Reply #13December 01, 2011, 01:55:23 am

Toby

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Re: Thermostat
« Reply #13 on: December 01, 2011, 01:55:23 am »
Try flushing the cooling system. DuPont no longer sells its 2 part radiator flush (which actually worked quite well) and only sells some one part BS that does not seem to do more than water alone.

You can do a really good job with a gallon of vinegar for the flush and washing soda for the neutralizer. Distilled white vinegar is available for about $2 a gallon from Costco or Cash & Carry and washing soda can be found at Ave Hardware and Wally World.

Just like the old DuPont stuff, drain all of the coolant and flush with water. I like to back flush the heater and radiator as long as I have the hose out. (for all of you kids that is running water BACKWARDS through the radiator/heater core) Add the vinegar and top up with water. Run it until it gets hot and then from 10 minutes to a couple of days. Drain the vinegar, flush with water and the add 1/2 - 3/4 cup of washing soda and top up with water. Run for ten minutes and then drain and flush with water. Add you antifreeze and drive happily on your way.

It is surprising how well this works. It will even clean the rust out of coolant bottles. If you drain it all into one tub the washing soda "neutralizer" corrects the Ph of the waste water making it safe to dump down the drain since it is not hazmat. Just stuff your mother had under the sink.

Reply #14December 02, 2011, 11:59:48 am

wdkingery

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Re: Thermostat
« Reply #14 on: December 02, 2011, 11:59:48 am »
Why is the cooling system @ 0 psi?

 

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