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would you drill a hole in this thermostat?

LPBlues

Member I
Hi all,
I'm having overheating issues in an engine that has just been inspected by a marine mechanic… (see my other thread about the temp sending line for background info if you're interested). I'm not that thrilled that this was not caught but stuff gets missed I guess. He has suggested drilling a hole in the thermostat below to prevent an airlock. I know some people do this, he seemed to think any mechanic worth his salt would do it without hesitation.

1) Recommended?
2) Where exactly to drill?
3) What diameter (I suggested 3/16" and he agreed that would be fine).

I posted this over a the Moyer forum too in case anyone thinks this looks familiar :). I just want to get to as many experts (self designated or otherwise) as possible...

image-1.jpg

image.jpg
 

LPBlues

Member I
thermostat a red herring too

So, I ran the old heat up the thermostat on the stove test and and it opened and closed at the appropriate temps. So either an airlock is actually the issue or there is a blockage somewhere else.
 

markvone

Sustaining Member
Neal,

I'm a big trial and error tester. I'd run the motor without the thermostat to see what happens before I drilled a hole in it. If no change, then no air lock and no hole required. I would think drilling a hole in the thermo would be common knowledge for mechanics and well documented on message boards if used to cure overheating as a common problem on the A4.

Mark
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
I seem to recall others commenting regularly, over the years, about airlocks in their thermostat housings.

Our Universal diesel has a small petcock at that point to vent out air bubbles. Last time I filled up the engine with new coolant from empty it took me quite a while to get those bubbles all out!
I would know that yet another one had worked its way up to that high point in the system when the temp gauge would quickly rise.
:0

Most recent coolant change was done by a mechanic that has rigged up a pump from a bucket to force-flow new coolant thru the system and force out the old stuff. That process was much faster and Pretty Nifty to watch happen.
:)

Loren
 

LPBlues

Member I
ran it without the thermostat tonight...

and the temps stayed around 130 occasionally getting to 136ish. It stayed like this for 20 min or more of idling and putting it into reverse etc. (while tied to the dock).

So given that the thermostat functioned fine in a pot of water I can only come to 3 possible conclusions:

1) The thermostat was gunked up enough to prevent it from operating correctly until my vinegar soak and brushing before the 'pot' test. It didn't look much worse before I cleaned it so I'm mostly discounting this theory.
2) There was an airlock forming under the thermostat that was preventing it from functioning normally. Drilling a hole could be an answer here but the thing has been in that engine most likely for over 30 years, why would that suddenly be an issue now? I think the leak might be a suspect here.
3) removing the Thermostat from the cooling system caused something that was creating a blockage to move or become dislodged, which I guess could haunt me later.

I'm leaning towards #2 at the moment because it seems the most likely.

Thanks everyone for your replies, I'm learning lots from you. If anyone has any thoughts on my conclusions above I'd love to hear from you.

So I may have solved one problem but now I found I couldn't get it into forward gear. I'll start another thread on that one if I get stuck :). There is prior history here with the previous owner, he was fixing this before the inspections and I think something has slipped (adjusting collar and pin). Anyway, it's looking more like I'll be able to take the boat out this weekend which is exciting.
 

Afrakes

Sustaining Member
Maybe?

LP: By removing the thermostat you have significantly reduced resistance to the coolant flow. Being the pessimist that I am I would still make sure that you don't have any other impediment to coolant flow. Just how "gunked up" was the thermostat? If that was "gunked up" what does that say about what may lie in other coolant passages. Al Frakes, Port Kent, NY
 

markvone

Sustaining Member
Sure sounds like thermostat related

Neal,

My only other thoughts are:

1) Did you load up the engine enough to fully warm it up to verify no overheating without the thermo?
2) Is the water colder now than when it last overheated?
3) Did you verify the engine was not overheating even if the gauge said +/- 130?

After I upgraded my Universal 5424 to the 3" H/E, I ran it in Feb with Bay water near freezing, I could not get the gauge to move. Even in gear with 2000 rpm for 20 min. It never overheated during the first few runs and even the coolant side and exhaust manifold were not hot, I could touch them. So the engine was just not loaded up enough in cold air and cold water to get it warmed up in 20 min. Also I'll bet air pockets were in with the temp sensor because several runs later, I could see rising temps on the gauge (130-140), then it would drop back on the peg, even though the engine was warm/normal temp. It finally started to heat up to 160 and stay there after several runs with all the air out. So the gauge can be off for various reasons and not match the engine temp.

So, drilling a hole in the thermo may be the logical next step since you can reverse it with a new thermo.

Mark
 

Bill Sanborn

Member III
A4 cooling

I agree with Mark, should run at full power in forward at the dock with no thermostat. 136F is too warm for running at idle. When these were salt water cooled the rule of thumb was to stay below 140F under full load to reduce salt buildup in the block. Reverse gear can slip so running in forward is better.

If you still have the original pump it might be time for a new one. Inside the pump is a "camming surface", a little bronze shoe that is mounted inside between the inlet and outlet ports. Over the years the shoe gradually wears reducing the volume of fluid the pump puts out. The shoe is replaceable but you said that the pump was leaking anyway and suspected the seals. If you do this consider replacing the coolant hoses at the same time.

I replaced mine several years ago with the Moyer pump. It uses sealed ball bearings so no grease cup. The cover also seals with an o'ring, a definite advantage.

Where in the Salish Sea are you? (that almost sounds like a curse:egrin:). If at Shilshole we might be neighbors.
 

LPBlues

Member I
I agree with Mark, should run at full power in forward at the dock with no thermostat. 136F is too warm for running at idle. When these were salt water cooled the rule of thumb was to stay below 140F under full load to reduce salt buildup in the block. Reverse gear can slip so running in forward is better.

If you still have the original pump it might be time for a new one. Inside the pump is a "camming surface", a little bronze shoe that is mounted inside between the inlet and outlet ports. Over the years the shoe gradually wears reducing the volume of fluid the pump puts out. The shoe is replaceable but you said that the pump was leaking anyway and suspected the seals. If you do this consider replacing the coolant hoses at the same time.

I replaced mine several years ago with the Moyer pump. It uses sealed ball bearings so no grease cup. The cover also seals with an o'ring, a definite advantage.

Where in the Salish Sea are you? (that almost sounds like a curse:egrin:). If at Shilshole we might be neighbors.

Good points, I plan on getting an acid flush done, replace hoses and probably replace that pump with a moyer one soon. It only made it up to 136 when I was flipping the thing in and out of gear and revving quite a bit. Most of the time it hovered around 130 or just below. I just want to get the dang boat out of the previous owners slip/marina and down to ours. Which is not in Shilshole, we're in Canada (Tsehum Harbour in Sidney) but we do like to get over to Friday Harbour etc. Now with the bigger boat we might make the trek down to Seattle sometime. I'd say we're still neighbours.
 

LPBlues

Member I
LP: By removing the thermostat you have significantly reduced resistance to the coolant flow. Being the pessimist that I am I would still make sure that you don't have any other impediment to coolant flow. Just how "gunked up" was the thermostat? If that was "gunked up" what does that say about what may lie in other coolant passages. Al Frakes, Port Kent, NY

Barely is how I would characterize it. The pics above show it after cleaning but If I'd taken pics before you might not have been able to see any real difference. Point taken about issues elsewhere. This is intended to be a temporary measure so I can just make the several hour trip to the boats' new home. I'm hoping to sail some of it. Once I get the boat closer to home I plan on doing a bunch of work and possibly replacing the thermostat, maybe with a new one that can drill without feeling guilty about wrecking a piece of cherished marine history :).
 

LPBlues

Member I
Neal,

My only other thoughts are:

1) Did you load up the engine enough to fully warm it up to verify no overheating without the thermo?
2) Is the water colder now than when it last overheated?
3) Did you verify the engine was not overheating even if the gauge said +/- 130?

So, drilling a hole in the thermo may be the logical next step since you can reverse it with a new thermo.

Mark

Thanks Mark,
1) not really. I didn't take it out of the slip. However my previous test the week earlier only ran at idle for about 7 minutes before it started overheating so this was a big improvement to stay near 130 most of the time for 20 minutes. More trials are needed for sure.
2) Probably not, given the short timeframe between tests (1 week) and our water tends to hover around 5-6 degrees Celsius at this time of the year.
3) Two things made it clear the overheating was real, one was the Heat exchanger was practically boiling when I managed to get the cap off and two, the oil filler pipe was literally smoking. Neither occurred during the trial without the thermostat so I'm fairly certain I wasn't getting false readings.

great questions though, thanks!
 

Stu Jackson

C34IA Secretary
I seem to recall others commenting regularly, over the years, about airlocks in their thermostat housings.

Our Universal diesel has a small petcock at that point to vent out air bubbles. Last time I filled up the engine with new coolant from empty it took me quite a while to get those bubbles all out!
I would know that yet another one had worked its way up to that high point in the system when the temp gauge would quickly rise.
:0

Most recent coolant change was done by a mechanic that has rigged up a pump from a bucket to force-flow new coolant thru the system and force out the old stuff. That process was much faster and Pretty Nifty to watch happen.
:)

Loren

We call it "Burping" your engine, whenever coolant is replaced:

Engine Overheating 101 - How to Burp Your Engine (Reply #6) http://c34.org/bbs/index.php/topic,4518.msg26462.html#msg26462

May not be applicable to A4s, but sure works for Universals.
 

LPBlues

Member I
Thermostat still a red herring

Finally got the forward gear working again but the engine overheated in the same place as last time, after about 30 min of motoring. So we sailed back again. I need to start taking more stuff apart and looking for restrictions. Next most likely place to look, according to the Moyer manual, is a restriction at the fitting for the water jacket side plate. Which I think involves moving the alternator and maybe some other stuff out of the way first…
 

Bill Sanborn

Member III
If you are running w/o the thermostat try blocking the bypass hose which goes from the forward end of the T on the side of the block to the thermostat housing. This will force all of coolant thru the block. As I posted in the prior thread, I installed a ball valve in this bypass hose and used in to regulate temp. This worked for years until I finally got around to installing FW cooling.

In the short run try a pair of vice grips to pinch off the hose, maybe with some padding on the hose.
 

jreddington

Member III
If you are running w/o the thermostat try blocking the bypass hose which goes from the forward end of the T on the side of the block to the thermostat housing. This will force all of coolant thru the block. As I posted in the prior thread, I installed a ball valve in this bypass hose and used in to regulate temp. This worked for years until I finally got around to installing FW cooling.

In the short run try a pair of vice grips to pinch off the hose, maybe with some padding on the hose.

My '84 E-28 converted to FW cooling has specifically a ball valve for the same thing. For years I did not know what its function was. It just sat there open. Then, pulled the heat exchanger for cleaning. Refilled with coolant (Sierra non-tox since this does run through my water heater). Kept getting overheat. Finally closed the valve and could hear a gurgle from the new flow. Added a little over a quart back in the resevoir (Level dropping was a good sign of venting air). Then reopened the valve.

I would suspect just pinching the hose would work as well. A couple pieces of waste pywood squeezed with a Vise Grip should work.

Jim R.
 

LPBlues

Member I
looks like we found it

So there was some buildup on the intake side of my heat exchanger, a hard white lump right where the raw water fitting comes in that closed that intake by about 50%. I chipped it off and got things back together and took it out for a motor yesterday and it never rose above 170 while running. much better. I'm sure there is still more that could be done and we'll be taking short trips for a while till the engine proves itself more but at least we can get out. Now all we need is some wind.

Thanks everyone for your advice!
 
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