8 replies to this topic

[Minwah]

My '79 850 has a water leak on the thermostat housing, the bypass hose is very split and the radiator has seen better days. That said, no real temperature issues, it just gets slightly hot in traffic and on very hot days as you'd expect. The coolant hasn't been changed for donkeys years so I'm expecting plenty of crap to be in the system.

 

I'd like to replace the radiator, hoses and thought I'd replace the thermostat & water pump while I'm at it. I have a few questions:

 

1) Are the water pump bolts likely to shear off? (I know the thermostat studs often shear but I replaced mine with stainless ones years ago so not so concerned about that.)

 

2) Should I flush the system *before* taking the rad/pump etc off? ie so that any crap in the engine/heater doesn't end up in the new rad/pump etc.

 

3) I've found various suggestions in old posts for stuff to use to flush/clean the system, with motorist specific products often shunned. Is CLR still a good recommended product to use for this?

 

Many thanks.

[Spider]

Probably answering in reverse order here !

CLR now have a specific Radiator flush, which granted, I haven't tried. I was using CLR for a number of years and found it good, but I looked away from it as there was the odd engine it was very slow to work on and I wasn't thrilled with the results, though, usually it would do the Trick. I've now gone to another product, which seems to be a commercial grade, ' Liquid Intelligence '. It's a 2 step process and is VERY good, though all up will take about 7 days to do a thorough clean.

Before cleaning, I will recommend removing the block drain plug and de-crapping that. I'm sure you'll find once you remove it, no coolant will flow from there. I use a few size drill bits, just turning by hand here, starting with a 1/4" / 6 mm bit and working up to the biggest I can get in there.

Given your description here, I would strongly recommend a cooling system clean before removing parts. Noted you are replacing your radiator, however, if when cleaning there's more solid pieces moving through the cooling system, you'll find they'll be more likely to get stuck in the radiator, which is best not with a new unit. You'll likely find the block and head passageways quite rusty, which is very poor for heat transfer (they say a 1/2" rusted plate has similar heat transfer to a 'clean' 6 - 8" plate).

I can't say if the pump bolts will be likely to shear off, I think you'll only find this out when you go to undo them.

I'm sorry, I am not a fan of Stainless Fasteners here. They are of very dissimilar metals to the block and will react with the block causing it to corrode in very quick time. They can also be sufficiently dissimilar to the alloy of the Thermostat Housing and Water Pump to also cause them to corrode here too. Stainless also has very poor tensile strength. When they break or become jammed from corrosion, being hard only makes them so much more difficult to remove. What I have found as a good solution here to stop plated fasteners from corroding or rusting in these applications is to just coat some ordinary grease over the threads and shanks of these bolts before fitting them. There is some better products on the market for this, however, I've found here, grease works perfectly well. I'm not sure what you have in mind for a radiator, but I would recommend a Brass / Copper unit for the reasons or dissimilar metals in the cooling system. These are also more efficient for cooling / heat transfer that an aluminum unit.

I would also recommend plugging up the By-pass. When the Thermostat opens, it allows a reasonable flow of hot coolant from the head to flow back in to the block, by-passing the radiator. When these were originally designed, best I can determine, they used a different style thermostat that hasn't been available since the very early 60's. That one had a sleeve on that that blocked the by-pass as the thermostat opened. Jags of the era had a similar Thermostat. Blocking this off, you'll find your heater will work better and the engine run cooler.

[Minwah]

Many thanks for your detailed reply!
 

CLR now have a specific Radiator flush, which granted, I haven't tried. I was using CLR for a number of years and found it good, but I looked away from it as there was the odd engine it was very slow to work on and I wasn't thrilled with the results, though, usually it would do the Trick. I've now gone to another product, which seems to be a commercial grade, ' Liquid Intelligence '. It's a 2 step process and is VERY good, though all up will take about 7 days to do a thorough clean.

It looks like Liquid Intelligence 239 is the stuff I need. It doesn't look like there is a UK distubutor but I'll contact the manufacturer and see how much it would cost to get shipped over.
 

Before cleaning, I will recommend removing the block drain plug and de-crapping that. I'm sure you'll find once you remove it, no coolant will flow from there. I use a few size drill bits, just turning by hand here, starting with a 1/4" / 6 mm bit and working up to the biggest I can get in there.

I was planning to remove the drain plug. I'm hoping it isn't too bad but we'll see...
 

Given your description here, I would strongly recommend a cooling system clean before removing parts. Noted you are replacing your radiator, however, if when cleaning there's more solid pieces moving through the cooling system, you'll find they'll be more likely to get stuck in the radiator, which is best not with a new unit. You'll likely find the block and head passageways quite rusty, which is very poor for heat transfer (they say a 1/2" rusted plate has similar heat transfer to a 'clean' 6 - 8" plate).

Thanks for confirming, I assumed that would be the best idea.
 

I can't say if the pump bolts will be likely to shear off, I think you'll only find this out when you go to undo them.

Sure, I'll give them plenty of penetrating oil beforehand and hope for the best.
 

I'm sorry, I am not a fan of Stainless Fasteners here. They are of very dissimilar metals to the block and will react with the block causing it to corrode in very quick time. They can also be sufficiently dissimilar to the alloy of the Thermostat Housing and Water Pump to also cause them to corrode here too. Stainless also has very poor tensile strength. When they break or become jammed from corrosion, being hard only makes them so much more difficult to remove. What I have found as a good solution here to stop plated fasteners from corroding or rusting in these applications is to just coat some ordinary grease over the threads and shanks of these bolts before fitting them. There is some better products on the market for this, however, I've found here, grease works perfectly well.

I hadn't realised that. I forget exactly when I put the stainless studs in, but I think about 10 years ago...it seemed like a good idea at the time. Perhaps I should carefully check whether they are seized and if not, replace them with standard studs with some grease.
 

I'm not sure what you have in mind for a radiator, but I would recommend a Brass / Copper unit for the reasons or dissimilar metals in the cooling system. These are also more efficient for cooling / heat transfer that an aluminum unit.

I was just going to fit a standard one, like this:

https://minispares.c...px|Back to shop
 

I would also recommend plugging up the By-pass. When the Thermostat opens, it allows a reasonable flow of hot coolant from the head to flow back in to the block, by-passing the radiator. When these were originally designed, best I can determine, they used a different style thermostat that hasn't been available since the very early 60's. That one had a sleeve on that that blocked the by-pass as the thermostat opened. Jags of the era had a similar Thermostat. Blocking this off, you'll find your heater will work better and the engine run cooler.

I wondered why people do that, thanks for the explanation. However would I need to remove the tube from the head and put a blanking plug in? Also would I need a different water pump without the bypass tube? Or can you just use a rubber bung in both tubes? I was planning on leaving it standard but with a silicon hose.

Thanks again.

[Lplus]

Removing the bypass and blocking the head/pump tubes (or using a bypassless pump) will leave the engine with no coolant flow at all until the thermostat opens if the heater tap is shut.  I understand the advice for fitting non bypass heads is to drill a few small holes in the thermostat plate to allow some flow past the thermostat.  Without that flow the thermostat could remain relatively cold even though the water was boiling elsewhere in the head.

[Spider]

 

I'm not sure what you have in mind for a radiator, but I would recommend a Brass / Copper unit for the reasons or dissimilar metals in the cooling system. These are also more efficient for cooling / heat transfer that an aluminum unit.

I was just going to fit a standard one, like this:

https://minispares.c...px|Back to shop
 

I would also recommend plugging up the By-pass. When the Thermostat opens, it allows a reasonable flow of hot coolant from the head to flow back in to the block, by-passing the radiator. When these were originally designed, best I can determine, they used a different style thermostat that hasn't been available since the very early 60's. That one had a sleeve on that that blocked the by-pass as the thermostat opened. Jags of the era had a similar Thermostat. Blocking this off, you'll find your heater will work better and the engine run cooler.

I wondered why people do that, thanks for the explanation. However would I need to remove the tube from the head and put a blanking plug in? Also would I need a different water pump without the bypass tube? Or can you just use a rubber bung in both tubes? I was planning on leaving it standard but with a silicon hose.

Thanks again.

 

One of those Radiators should be OK. I don't think there's much option these days for a new unit. If your radiator is blocked but in otherwise good condition, I would suggest having yours overhauled.

There's a few options here for plugging up the By-pass. There is a Factory Cap for doing the job;-

http://www.minispare...|Back to search

 

You could fit one of these on the Head and if you already have a Pump, fit one on that too, however, if you are yet to purchase a Pump, a GWP187 Pump is already plugged up. If you ever have the Head off at some future time, you could then plug the By-pass in a more effective way, however, I wouldn't pull the Head just to plug it.

There is no need to modify the Thermostat in any way and in fact, I would discourage it. Drilling Holes in it effectively by-passes it. I would suggest leaving it as is and let it do it's job. When the Thermostat is closed, while there'll be no normal circulation, the warm coolant will rise to the Thermostat regardless, just as it would say in a kettle - we heat it from the base, but that warm water from the base rises to the top and pushes the cooler water down to the base, so it in turn heats and rises and on and on it goes until the Thermostat begins to open. If you are concerned about the Pump building up pressure in the system, it may build some, however, it won't be much at all. The Pump is a Centrifugal design and the correct way to shut off flow from them is to close the Outlet, they are not a positive displacement pump, so the pressure developed is quite limited.

[Minwah]

One of those Radiators should be OK. I don't think there's much option these days for a new unit. If your radiator is blocked but in otherwise good condition, I would suggest having yours overhauled.

It doesn't look too good but I'll see what it looks like after flush and have a good look when I take it out.

There's a few options here for plugging up the By-pass. There is a Factory Cap for doing the job;-

http://www.minispare...|Back to search
 
You could fit one of these on the Head and if you already have a Pump, fit one on that too, however, if you are yet to purchase a Pump, a GWP187 Pump is already plugged up. If you ever have the Head off at some future time, you could then plug the By-pass in a more effective way, however, I wouldn't pull the Head just to plug it.

The pump without the bypass is meant for bigger engines really, not sure if it's suitable for an 850. I was considering rebuilding the original pump if it's serviceable as I don't think the new replacements are the same shape.

I'm not yet sold on bunging the bypass pipes as that would possibly be more prone to leaking than the hose, and just as awkward to replace...

Watched some videos of the Liquid Intelligence 239, that does look like good stuff!

[Spider]

The pump without the bypass is meant for bigger engines really, not sure if it's suitable for an 850. I was considering rebuilding the original pump if it's serviceable as I don't think the new replacements are the same shape.

I'm not yet sold on bunging the bypass pipes as that would possibly be more prone to leaking than the hose, and just as awkward to replace...

Watched some videos of the Liquid Intelligence 239, that does look like good stuff!

 

The Pumps were standardised across all engines from the late 60's, if your engine is original to your car, then this pump will fit.

I agree with those caps not being the best method of plugging them, however, it is a factory item. Shortly after your car was made, they did away with the by-pass in this location. A client of mine manufactures and tests pumps, years back when I showed their test engine these pumps, he said right off the bat that the location of that by-pass take off on the pump would lead to early low speed cavitation. I'm not sure if that was why the factory did away with them. The Factory eventually didn't drill and tap the heads to plug the by-pass, however, in the interim, they fitted these caps.

[timmy850]

Another option is to get a bypass-less pump which has the blank spigot and then use a good quality rubber hose in the same position as usual to blank the head side

Eg one with the bypass outlet added but not drilled
https://classicmotor...-no-bypass-hole

[Minwah]

Thanks, I didn't think the non-bypass water pump (which has the large impellor) was suitable for an 850, but it seems it's only the very early ones it won't fit on.

 

One other thing I was wondering about...considering I only really use the car in spring/summer when it's warm, would it be a good idea to use an 82deg thermostat, or is it best to stick with the standard 88deg one?