VWDiesel.net The IDI, TDI, and mTDI source.
General Information => Troubleshooting => Topic started by: jimfoo on November 25, 2011, 12:16:18 am
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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!
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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..
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Does it overheat without a thermostat installed?
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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.
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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.
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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..
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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.
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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.
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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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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.
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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.
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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.
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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.
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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.
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Why is the cooling system @ 0 psi?
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Why is the cooling system @ 0 psi?
Evans is waterless coolant, and requires 0psi for it to work correctly..
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I do not think it requires 0 pressure, just that it does not need to be pressurized to operate in the normal ranges for internal combustion engines. I do not think it would generate any significant pressure in a closed system anyway.
The over the road truckers are using it to run much hotter coolant temps thereby increasing efficiency of their big diesels. IIRC north of 250*. 1/2 a mile per gallon is big money when a fleet runs millions of miles a year. Might be something to try in a VW diesel. Maybe there are a couple of MPGs in it for us.
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i would be TERRIFIED to run my VW diesel that hot.. that wont give you much overhead before your oil temps and such get to lethal temperatures..
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With good reason. Any water based coolant has long since flashed to steam in the hottest areas of the head forming transient pockets of steam. Steam does not cool well. Evans, on the other hand, keeps all of those areas wet, and therefor cooled.
Oil temps are an issue, but that just means synthetic oil and maybe a bigger cooler. I intend to try it in my XR4Ti and the LBGTD.
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With good reason. Any water based coolant has long since flashed to steam in the hottest areas of the head forming transient pockets of steam. Steam does not cool well. Evans, on the other hand, keeps all of those areas wet, and therefor cooled.
Oil temps are an issue, but that just means synthetic oil and maybe a bigger cooler. I intend to try it in my XR4Ti and the LBGTD.
ok, you can be the test guinnea pig.. im not gonna risk it on any of my cars. 250* just sounds like its asking for problems..
i wouldnt be hesitant in a DI engine, but an IDI where the head already has a hard enough time with heat, no way..
im sure IT DOES HELP with the DI engines quite a bit. i know they have a problem maintaining heat sometimes in cold weather just because they are soo efficient.
but being the nature of the IDI, and inherent problems with getting the heat away from the pre-cups, it just doesnt sound like something i would be willing to try without knowing the exact outcome before hand..
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I think I might have figured out the problem. The cooling system design. I think the system was designed to work in a certain configuration, and not having the engine in a VW, I no longer have a configuration that will work within the designed parameters. The thermostat is on the cold line, so hot and cold water have to mix. I think my system has too much capacity and cooling. Since my cold side doesn't get hot, the hot side has to get extra hot to be able to blend down to the opening temp of the thermostat. To fix this, I am going to put a remote thermostat on the hot side and take out the stock thermostat. I found I run a little cooler by completely pinching off the bypass hose, and just having the bypass water through the heaters(which are currently my "radiator" as the thermostat never opens much) the thermostat I found has a bypass that gets blocked off at temp, in and out, and a heater hose port, so should be relatively easy to retrofit. The only downside is that it is permanently encased in plastic, but is only $25. I believe this will fix all my heat problems. I get it tomorrow, and should have it on by Saturday, so I will let you all know how it goes.
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(http://www.66rover.com/temp/Stat.jpg)
Got the thermostat today. Letting the car cool down, then in it goes ;D
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That looks like my air manifold that I put in my oil system...only plastic and not threaded. Will you show a pic when done. Also some of your ride. I am thinking of building one only keep it IDI.
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WOOT!!!!!! I just got back from my test hill, which with the stock thermostat I would be up to 230 by the top. The temp climbed to 195, stat opened and the temp dropped to 180 and stayed between there and 190, all without my fan coming on.
As for my ride, I have pics here http://www.66rover.com/mods/mods.html, although you may have seen them from back when I was on the board a lot. I don't know that a pic of the thermostat mod will help as you can't see enough as other things are in the way. What I did was cut the upper hose between the engine and radiator and put it there. I took the stock thermostat completely out I plugged the bypass hose coming from the head, although some day it will get a fitting without a bypass. The slightly smaller fitting on the very end of the thermostat, opposite the radiator end, got hooked to the bypass fitting on the water pump. The slightly larger fitting on the thermostat went to my second heater.
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BTW, the thermostat is off of a P38 Range Rover, year range of around 2000. I got it from a local shop for $25.
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I think I might have figured out the problem. The cooling system design. I think the system was designed to work in a certain configuration, and not having the engine in a VW, I no longer have a configuration that will work within the designed parameters. The thermostat is on the cold line, so hot and cold water have to mix. I think my system has too much capacity and cooling. Since my cold side doesn't get hot, the hot side has to get extra hot to be able to blend down to the opening temp of the thermostat. To fix this, I am going to put a remote thermostat on the hot side and take out the stock thermostat. I found I run a little cooler by completely pinching off the bypass hose, and just having the bypass water through the heaters(which are currently my "radiator" as the thermostat never opens much) the thermostat I found has a bypass that gets blocked off at temp, in and out, and a heater hose port, so should be relatively easy to retrofit. The only downside is that it is permanently encased in plastic, but is only $25. I believe this will fix all my heat problems. I get it tomorrow, and should have it on by Saturday, so I will let you all know how it goes.
I wanted to bump this as I think it will be useful for those putting a VW into a non VW type cooling environment.
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maybe your temp gauge is not reading right. use a hand held infa. red gun type to check temps at all points. they are perry check to buy now.
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maybe your temp gauge is not reading right. use a hand held infa. red gun type to check temps at all points. they are perry check to buy now.
i believe replacing his thermostat with the one pictured, solved his problems...
this is ah OLD thread BTW.. hasnt been viewed in a LONG time..
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That is why I bumped it. I will probably use this thermo deal in the Heep TDI I am building.
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That is why I bumped it. I will probably use this thermo deal in the Heep TDI I am building.
try to keep the t-stat in the original location first..
the original location is actually very good..