Water Bypass Valve - were does the water go?

[wilgil]

Hi all. Will from New Zealand here.

I am having problems sorting outmy old HF 105's overheating issue. So far i have replaced the water pump, impeller, thermostat and temperature sensor. All of the compressions (cold) are approx. 125. Since installing the new impeller plenty of water is coming out of the two vents as well as the pee hole I installed. The over temp alarm only goes off at high revs, and stops within 10 or so seconds after slowing down to non-planing speeds.

I replaced the water pump as the old one was falling apart after
ingesting quite a bit of mud/stones after becoming beached a few
months back.

Apart from this the old girl goes great. A knowledgeable mechanic told
me (with an evil grin on his face)that it would probably be the Water
Bypass Valve - my Clymer manual doesn't even mention the existence of
one.

When it happened the other day I did a bit of on the water fiddling
and removed the thermostat - the alarm didn't go off after this, but I
reckon that it's fitted for a reason, so it should be there.

Funny thing - when i was checking it out the motor seemed to run much
better (faster) with the cowl off - my wife complained about the noise
though!

In order to gain access to the bypass hole (105 '75) for cleaning, I got out the trusty hole saw and drilled a 4 cm diameter hole through the bottom
cowling. I can always cover it with a 'service' plate. I cleaned it
all out and then I reasoned that if I forced water down the head
cooling hole (after the thermostat), water should come out the water
bypass hole, right? Wrong! What actually gets cooled first - the
cylinders? The head? I tried to force water into the bypass hole to -
no go. Do I have a major blockage?

Even though the compressions checked out ok, I removed the head (that is a story in itself) and I noticed that one of the combustion chambers was very clean - that would suggest water ingress?

I've now got to order a new head gasket, but i don't want to put it all together unless the cooling system is working as it should. I can't find any obvious blockages, and now everything is pretty clean. It's a good old motor and I don't have the $$$ to replace it (currently unemployed, waiting for new job to start).

Why doesn't any water go to the bypass hole????

Thanking you all in advance!

 

[Frank Acampora]

Re: Water Bypass Valve - were does the water go?

FIRST: If you removed the thermostat and the cooling problem stopped, you have a bad thermostat. leave it out or replace it. Yes, you can leave out the thermostat and the engine will run quite happily with no harm. The open thermostat only cools the head--more later.

Now for the water circuit: Water comes up the water tube from the pump and enters match plate. It makes a 90 degree turn and at the pipe plug which you can not remove, it turns 90 degrees again and enters the block. At the point where it enters the block, there is a bypass valve (which was discontinued in later models.). This valve is located on the block at the dog-leg on the lower front exhaust cover plate and is covered with a diamond shaped plate held with two 10X24 hex head screws. This valve opens when there is excess pressure in the cooling system and dumps water back down into the engine leg. If you were able to remove the plate without snapping off the screws, you were very lucky. When you replace them be certain to liberally coat them with anti-seize.

Water now continues into the block and first circulates around the exhaust chamber. Since there is always exhaust present when the engine is running, it is critical that water cools the chamber and walls at all times.

Water also enters the area around the cylinders and a small amount always circulates because there is a weep hole in the thermostat. This allows hot water to flow over the thermostat expansion element and allow faster opening of the thermostat as the engine heats up.

Once the thermostat opens, full water flow is maintained around the cylinders and through the head from top to bottom. This water is now dumped through the bottom of the head into the engine leg. Once in the engine leg, a little pressure at the exhaust idle relief valve blows some out the two idle relief holes in the rear shroud, usually as a spray. Later, on the water when the engine is running fast, a lot of water will exit these holes as a stream. However, the bulk of the water will exit the exhaust snout with the exhaust.

The idle relief functions to relieve exhaust pressure in the exhaust chest when the engine is sitting deep in the water, like when idling or moving slowly off plane. Under these conditions, water is high inside the leg and it would take excess pressure to blow it out the snout behind the prop. This pressure would cause exhaust gas to be aspirated back into the cylinders through the open exhaust ports and cause a rough idle or stall the engine.

Remember I wrote that the water bypass valve was discontinued on later models? If the bypass valve is clogged, then nothing will happen! The water pump acts as a centrifugal pump at high speeds and simply will not deliver excess water--no harm, no foul. On the later models, the cast hole was left in the block, but it was not drilled into the water passage and the hole was not capped. For you Force owners, that is why there is still the hole in the block and the dog-leg on the lower exhaust cover--it was cheaper to leave it there, unused, than to change the molds.

If you try to put water into the head after the thermostat, it will simply run down the head and into the engine leg. If you try to put it into the bypass with the plate, spring, and plastic valve removed, then again it will only go down into the engine leg if the bypass is not clogged.

This same exhaust and cooling arrangement was used with minor modifications on all Chrysler and Force three and four cylinder engines until the Force brand was discontinued.

 

[wilgil]

Re: Water Bypass Valve - were does the water go?

Fantastic answer as always, Frank - thanks.

I am concerned that I can't get any water to flow back up through the Bypass Valve hole. It looks clear, but there is no flow at all even when supplied by the high pressure garden hose.

If there is a major blockage in there, how could I possibly clear it?

If I have to give up on this motor, I have a tidy 3 cylinder 90 that I could fit to the boat. If the prop. shaft output of the 105 is closer to 90hp, does the same apply to the 90? (i.e. about 80hp). My boat is rated for up to 250HP and the 105 has a top speed of only about 50kph.

Thanks again.

 

[john from md]

Re: Water Bypass Valve - were does the water go?

Wilgil,

Drop your timing back to 28 degrees and see what happens. I have done that on several of the early engines and the overheat problem goes away.

I believe that this is because the gasoline sold then and that sold now are of different makeup.

Hope this helps,

John

 

[wilgil]

Re: Water Bypass Valve - were does the water go?

Thanks for the suggestion. Here in NZ we have 91 and 95 octane (both unleaded) - I always run the old girl on the 91. But as part of the major overhaul she is getting, timing would be a sensible thing to do. Thinking about it, it will be much easier with the head off too - TDC should be pretty easy to find when i can actually see the pistons!

 

[wilgil]

Re: Water Bypass Valve - were does the water go?

Frank - If I block off (by filling with a Metalset type epoxy) the bypass valve hole, then I won't have to worry about it ever getting stuck open or corrosion causing the block to break out at that point? It would also solve my little problem of the broken off screw - your thoughts?

Re. the thermostat - another site claims that i MUST always run a thermostat. I trust that you have had enough experience with these engines to know what you are talking about. It's also one less item to go wrong when I'm out on the briny - likewise the removal and blocking procedure i am suggesting for the Bypass Valve hole.

Should I use a gasket sealant when replacing the Headgasket?

Thanks again!

 

[Frank Acampora]

Re: Water Bypass Valve - were does the water go?

Obviously, the engine was designed to run at 160 or 180 degrees. The pistons are cam ground, that is, egg or oval shaped in cross section so the uneven heat they get from the exhaust and bypass side makes them "perfectly" circular at operating temperature.

Many people will assume that changing the temperature by leaving out the thermostat will change the expansion of the piston and they would be correct. This will change the shape of the piston and the seal of the piston skirt. This will change SLIGHTLY the inducted charge. Although the efficiency of the engine will be slightly less, you won't be able to notice it.

The rings will seal as they normally do so compression ratio will not suffer.

SO: While it is best to install a thermostat, it is not absolutely necessary to do so. You are certainly not going to wear out the engine in one run. Much more damage will be done with one overheating. Understand that while I would run without a thermostat if necessary, all my engines are equipped with one.

NOW: On to the water bypass valve. At the base of the cast hole is a drilled hole the size of the cross on the plastic valve. This hole communicates with the actual water passage going into the block. Filling this hole with epoxy is risky as you may reduce the size of the water passage.

As water comes out around the valve, it exits below the valve through a square hole below it about one inch inward from the edge of the block. This square hole is very difficult to clean with the engine assembled. You can try but I know you will start "saying your prayers."

Although Franz thinks Clymers is only good for starting your fireplace or used as toilet paper, It does have some decent information. For example: there are two different lengths of cover plates. Each uses a different length spring. Too short a spring on the short cover plate will let the valve open too easily. Thus his instructions "Stretch the p*ss out of the spring." Remember, Franz was (and still is) an excellent Chrysler dealer and thinks differently about aftermarket publications and parts. He has probably forgotten more than I will ever know. I will admit though, my 1988 Force factory manual does make the Clymers pale in comparison.

If you don't want to use the bypass, I would leave the plastic valve in it without the spring and then fill the hole with black RTV silicone. That way, it would be easier to remove in the future if necessary. Just be certain to rough up the interior walls so the RTV gets a good grip on them and won't blow out. The actual water passage is more than 1/2 inch in diameter so it almost never clogs. I doubt you need to worry about it.

And last night I neglected to mention, at the bottom of the block back by the head is another water drain from the passage around the cylinders. This communicates with the match plate drain from the head and ensures that water will ALWAYS circulate through the exhaust chest and around the cylinders even if the weep hole in the thermostat is blocked. Thus my statement that the thermostat only controls flow to the head. It does and it doesn't. If you have a block off the leg, look at it and you will see the water routes.

DO NOT use sealant on the head gasket UNLESS you have water weepage on the outside of the block that you can't stop any other way. Then, only use it on the outside surfaces; never the cylinder walls and head mating surfaces. As I have written before, in my engines I prefer to re-use the original head gasket if it is in good condition. It is already compressed by heat expansion and usually does not need to be re-torqued after the first run. Of course, when I rebuild for someone else, I always use a new gasket--eliminates the impression of shoddy workmanship. For me, it is a question of trust and honor; two values that are sadly lacking in many people today. The owner may not know what I did, but I will!

 

[wilgil]

Re: Water Bypass Valve - were does the water go?

Thanks Frank - I take it all on board what you have said. Thanks also for taking the time to look at what was said on the Chrysler Crew website by Franz.


'For me, it is a question of trust and honor; two values that are sadly lacking in many people today. The owner may not know what I did, but I will!'

It's too bad that there aren't more people in the trade like you. Trust, honor, integrity and honesty are values that I live my life by, and I never fail to be surprised by how others are completely happy to gain at the cost to a fellow human being these days. Maybe it's always been that way, I just notice it more now that I am more 'mature' (46 this year).

But getting down off my soapbox, I am now ready to reassemble everything and be reasonably confident that the whole lot won't go up in my face.

I promise to post back after the initial run!

 

[wilgil]

Re: Water Bypass Valve - were does the water go?

I took the old girl out today. The alarm went off within about 5 minutes. I took the thermostat out - the alarm took a while, but still sounded. The motor was running sweetly - the water coming out of the pee hole was approx 60-70 deg. C (calibrated finger). There was a good stream of water coming out as well. In the end I disconnected the alarm. The motor ran fine all day even at WOT. If it was overheating surely it would have seized or at least let me know that it was too hot?

Next step is to replace the impeller (I left the old one as it looked and felt good, but i have a new one on order and I will fit it).

I'd like to install a temperature gauge so that I can SEE what's happening.

My over temperature switch is white. I suppose it could be that?

Have i covered everything?

 

[john from md]

Re: Water Bypass Valve - were does the water go?

Back to my original suggestion, back the timing off to 28 degrees before you go tearing into anything. It only takes a half hour to do.

You can buy a handheld thermal sensor from Harbor Freight company for $20 bucks or so. Have someone aim it at the head while you are going WOT and you will see what your temperature is.

Disconnecting a warning system has dire results in any application and will void any insurance you may have. If someone gets injured and it is related to your actions, you can be held responsible. The risk isn't worth it.

Regards,

John

 

[wilgil]

Re: Water Bypass Valve - were does the water go?

I'm not so stupid as to not have a warning system, no worries there. I am going to try to find a combo thermal switch/sender so that I can have a gauge PLUS the alarm if I'm not attentive enough keeping an eye on my instruments.

I did read somewhere that the thermal switch was replaced with a higher temp unit - apparently they are red in colour, but I can't source any here in NZ.

I have a temperate sensor for my multi meter - when the engine is warmed up the temp is approx. 70 deg C (without the thermostat) measure coming out of the pee hole. The head are is not so hot as to stop me resting my hand on it for 5-10 seconds (that's with it running about 3000 rpm - with the temp alarm sounding).

The motor runs perfect.

I AM going to do the timing - I have a digital caliper that I can use for the stroke of the piston, but I'm unsure regarding the stroke distance from TDC that equates to the 28 degrees.

Can anyone take me through the maths?

Thanks.

 

[john from md]

Re: Water Bypass Valve - were does the water go?

How many timing marks are on your flywheel? Some have only 1 others have three. If you search for timing or timing marks etc, I know that Frank A has explained it numerous times. Let us know if you don't have any luck.

Regards,

John

 

[Frank Acampora]

Re: Water Bypass Valve - were does the water go?

Don't make your life more difficult than it needs to be. I get the impression from you that the engine is a distributor ignition engine. If that is a distributor ignition engine you can static time it using no measuring or math.

The ring gear on the flywheel will be marked 0 degrees and 36 degrees. On the front of the block above the top carb should be a bent metal pointer with a large line and several smaller ones. The large line represents either 0 degrees or 36 degrees, so at full throttle, the 36 degree mark on the flywheel should be four lines to the left for 32 degrees.

To static time the engine, remove all four plugs and ground them. Advance the control lever to full throttle. With the ignition switch on, turn the fkywheel by hand until the 36 degree mark is close to the pointer. Now as you continue turning, watch for the spark on the top plug. If it occurs when the 36 degree mark on the flywheel is to the left of the pointer large line by four small lines, it is correct at 32 degrees BTDC.

If you don't have the small lines, then count the number of teeth on the ring gear and divide it into 360 degrees. Now you know how many degrees each tooth represents.

If by some chance you do not have the bent metal pointer, salvage one off another engine--it was basically the same part for all three and four cylinder engines. Lacking that , make your own pointer from some sheet aluminum or such.

If you install a temperature gauge, the sender goes in the hole in the top of the head. This hole is plugged with a stainless slotted head pipe plug (1/8 NPT) and will be difficult to get out.

To wire the gauge, you connect power from the "I" terminal of the ignition switch to the power terminal of the gauge. A wire goes from the ground side of the gauge to the top post on the sender. The sender has variable resistance with temperature so as the engine heats up and cools, the sender allows more or less voltage to ground thus letting the meter read it.

The orange wire can be used for either a temp alarm or a gauge, but not both at the same time. If you want both, you must run another wire back or disconnect purple from the voltage regulator and use that. (Unless it is being used for a different tachometer)

YES! At one point during the very early 1980s I believe that Chrysler derated the 105 to a 90. This was when the industry decided to change from HP rating at the crankshaft to rating at the prop.

 

[wilgil]

Re: Water Bypass Valve - were does the water go?

Thanks John and Frank for the replies.

I checked the compression yesterday - all 120, BUT one of the plugs was clean. I mean REALLY clean - what gives?

I'll take the thermostat cover off and into an automotive store and hopefully fit a temp sender that will fit the thread. Either that or I will re tap the hole. I was using the hole for the pee hole.

Will

 

[john from md]

Re: Water Bypass Valve - were does the water go?

If one plug is burning real clean, chances are that it is burning too lean. Have you adjusted the carb mixtures? If so, maybe you have a float that is too low or a varnished jet. You need to take a look at this before you melt a piston!

John

 

[Frank Acampora]

Re: Water Bypass Valve - were does the water go?

Or a water leak into the cylinder. Water turns to steam from the combustion temperature and scours the plug and head clean.

 

[wilgil]

Re: Water Bypass Valve - were does the water go?

I haven't touched the carbs - I'm afraid that it might be a water leak - but the compressions all all even, dammit!

I've just purchased a water temperature gauge and will work out how to fit it in the weekend.

Just to confirm - if the water temp is ok, there's no way that the engine can be over heating, right?

 

[john from md]

Re: Water Bypass Valve - were does the water go?

I don't know if that is true or not. Frank will have to chime in here as I cannot recall the water jacket path.

Water is always coming out of my pee hole which is connected to the port next to the thermostat. This tells me that, water is not circulating through the entire powerhead until the engine warms up. It may be possible for some internal passages to be parially or entirely blocked and you would still get water to that port. This may show an acceptable temperature while the engine is actually cooking.

Again, this is only a theory as I have not had to trouble shoot too many water system problems in the powerhead. Lets see what he has to say.

John

 

[wilgil]

Re: Water Bypass Valve - were does the water go?

Hi John (and Frank)

Well, I fitted the temperature gauge in the weekend - the sensor screwed straight into the thermostat housing where the tell tale nipple was. (I now have to find a new spot to fit that).

I took the old girl out and gave her a thorough thrashing. The motor ran smoothly all afternoon over all rev ranges (except for the slightly 'hairy spot' I have always had just under planing speed).

The temperature came up to about 60 deg. C and didn't really move from that regardless of how hard the engine was working. This was all with the thermostat itself removed, so it's pretty much what I would expect. This weekend I will refit the thermostat and then I would expect a reading of about 80 Deg C (I think the 'stat opens at about 83 deg C).

If the engine was overheating and the water temperature didn't reflect it, I would say that she would be well and truly cooked by now.

I haven't checked the plugs yet, but I have a feeling that the #3 cylinder plug will be clean again - not sure what I can really do about that. I will re-torque the head with an accurate torque wrench and hope for the best I suppose.

I have yet to check the timing! I know - I've been slack, but it's the middle of Summer over here and the boat garage gets pretty darn hot, so I have to wait for the evening to work on the boat - and by then there's good stuff on the TV, and the animals have to be fed, the wife wants company, etc......

This weekend for sure!