1800: P1800 Rad/Expansion bottle problems

[Kevin 1964]

Hello All,

Had the car (1964 P1800) go into the garage for some clutch work & a basic service whilst up on the ramp. Oil change, coolant change etc. and now have issues that I didn’t go in with.

Although I’ve never had any cooling issues before the car, I barely made it home (about 2/3 of a mile) before the radiator emptied into the expansion bottle which in turn ended up bone dry with the contents on the drive. I let it cool down for quite a while and refilled the rad and part of the bottle. I left it is idling on the drive for approx. 15-25 before the same happened, days later tried changing the thermostat, same happened. One idea was to change the head gasket, done (probably needed it though), 15-20 mins later same rad/bottle issue again.

Was told later, try running without a thermostat, tried that…worked, went for a quick drive for about 30 minutes in the motorway, seems OK.
One week later, went for a spin around the corner, got back home and started to hear the dreaded knocking from the rad, looked on the floor to see expansion bottle contents. This time a small puddle instead of the of the usual rad/bottle full.

Found out after, that the garage on changing the coolant, changed a few hoses and the thermostat (which has been since changed again and then removed), none the wiser as to why its happening.

Any ideas, as at the moment as I don’t want to move it until I know how to fix it?

Regards,
Kevin

[Burdekin]

When filling raise the front of the car as high as you can and raise the expansion bottle as high as you can to remove any air. Then only fill expansion bottle to minimum level marked on the bottle.

[c1800]

Not advisable to run without the thermostat. There is a plate on the bottom of the thermostat which, when the thermostat opens, allows the coolant to circulate through the block. Without a thermostat proper cooling doesn't happen.

Make sure that the thermostat is the correct one. Notice the plate at the bottom.

https://classicvolvoparts.co.uk/part...ts_and_Housing

[142 Guy]

First off, whoever advised you that running without a thermostat was a fix should be avoided in the future.

I am not particularly familiar with the P1800S history (being the 142 Guy!). That said, in the time line of the B18 the type 1 engine (75 hp) had a pressurized system and the type 2 engine (85 hp) had a sealed system (expansion bottle). Not being an 1800 expert, 1964 seems early for a sealed system. Is your car a genuine type 2 engine sealed system or is it a retrofit or has somebody just added a catch tank on to the original pressurized system?

The reason this matters is that when filling (or a major top up of) the cooling system on the sealed system, the system must be filled from the radiator. The procedure is with the heater valve open and engine cold, fill to just below the neck of the rad cap opening and then start the engine. As the engine runs, burps air pockets and comes up to temperature the level will likely drop at which point you top up. As the thermostat opens the top hose should heat up (as will the coolant in the top of the rad). At the point the coolant approaches the overflow point in the rad opening, shut the engine down and cap the rad. Fill the expansion bottle to the mid point and replace cap. As the engine cools the coolant will contract sucking coolant out of the expansion bottle. If it drops below the low level, top up the expansion bottle to no higher than the mid point. All minor top ups of coolant are done from the expansion bottle.

Note that if you have the type 2 sealed / expansion bottle system you must never over fill the expansion tank. The expansion tank needs 'space' to allow for coolant expansion. If you overfill the system the pressure cap on the expansion tank will release when the engine comes up to temperature burping coolant over the engine compartment and driveway.

If you have a pressurized system with an over flow tank the fill procedure is similar; but , the details on how much to fill the rad are different. I have never owned a car with a pressurized system so best to consult the service manual.

From your description of the behavior of your system, it does not seem to be a true sealed / expansion bottle system. Is it possible that it is the original pressurized system and that somebody has retrofitted a catch / overflow tank to the radiator? The 'tell' between the two systems is that on the original pressurized system the pressure cap is on the radiator filler. On the sealed system the cap on the radiator is just a simple cap that seals the filler on the radiator. The pressure cap is on the expansion tank. An overflow tank retrofitted to a pressurized system will just have a simple sealing cap.

If you truly have the later type 2 sealed system with expansion tank, is it possible that the garage got confused and switched the expansion tank cap and the rad cap. On my 1971 140 with the cross flow rad the two caps are physically not interchangeable. However, on the very early cars which started out with pressurized rads perhaps it is possible to interchange the caps.

One idea was to change the head gasket, done (probably needed it though), 15-20 mins later same rad/bottle issue again.

'The' head gasket? Very strange. The head gasket can fail on a severe overheat although this is less likely on the cast iron B18/B20 than the later aluminum head engines. If you thought you had a head gasket failure you would always check with a compression test first and a coolant system pressure test to confirm that there was leakage between the combustion chamber and the cooling system. Reagent tests will also flag leakage of combustion products into the cooling system. However, if the leak is bad enough to over pressurize the cooling system that should show up with a compression test / coolant pressure check. I would not go through the 4-5 hour hassle of a head gasket replacement because of 'it might be a problem'.

If none of the preceding turns out to useful or relevant, I have three final suggestions.

The first is a pressure test of the cooling system. If you have a sealed system you will need to arrange to test the system to confirm that both the rad cap and the pressure cap are sealing. The pressure test will allow you to confirm the operating pressure of the pressure cap.

On my B20E, the thermostat has a flap on the bottom of it which closes off a by-pass in the cooling circuit. If the B18 has the same arrangement, some of the aftermarket thermostats that are sold for the B18/B20 will fit; but, lack the flap or have a flap that does not achieve closure. Something to check if your 'shop' replaced the thermostat - did they give you back the original?

If they changed some heater hoses, is it possible that they bollixed the hose installation. The heater is not in the normal coolant loop; but, some reversed connections might create some interesting problems (I am really reaching on this one!).

[Ron Kwas]

Kevin;

Good info from 142G! If problem started only after "service", it's likely they mucked something up in either the servicing or simply the refilling of Cooling system!...and I agree with him about the "run without a TStat recommendation"!

Questions: Was Cooling Sys refilled with equal amount that was drained?...was CS burped of air at refilling?...was replacement TStat a bypass type?...what was temp rating?

Simple as they are, the vintage Volvo (clearly with a retrofitted) sealed CS with overflow does have a specific fill procedure and things to watch for when servicing, that a mechanic used to more modern vehicles might not be familiar with...

Suggested reading: https://www.sw-em.com/Cooling_System.htm

Cheers

[c1800]

I’ll be interested to find out if the correct thermostat was installed. Many reports of poor quality thermostats , even with the correct configuration to close off the bypass, failing to do the job.

AFAIK, Calorstat and Wahler are the typically recommended higher quality thermostats.

Others like Stant get poor reviews.

[Kevin 1964]

Thanks all, about to fit a Brookhouse thermostat and start again.
Thank again for the feedback, its appreciated.

[Kevin 1964]

Hello 142 Guy,

Thanks for the feedback, from what you have said, my set up seems to be the sealed system from your description. The rad cap is just a cap and the pressure cap is on the expansion tank. This has been the set up since I purchased the car 6+ years ago and I have always topped up the radiator, never the expansion bottle which is something I know the garage was filling up. The caps are also different sizes and are not interchangeable

I would not be surprised if it had been modified over the years though.
I have attached a photo.

Thanks again

[142 Guy]

Yes, it looks like you have the later sealed cooling system with expansion tank which may be original or could have been a retrofit.

The cap on your rad looks very 'crusty'. When your problem occurs, are you losing coolant from the expansion tank or from the rad cap (where it is crusty). My 142E has the same rad seal cap as your 1800. Years ago I did a complete resto on my 140 which included a new rad cap. I discovered that the new rad cap was a leaker because it was manufactured incorrectly - the retaining ears on the cap were positioned incorrectly with the result that it did not seal tightly against the filler neck on the rad. I had to cut a couple of sheets of brass shim to fit under the rubber seal of the cap to get it to fit tightly. The cooling system is designed to operate under pressure which suppresses the boiling point of the coolant. If the rad cap is not sealing you will get premature coolant boiling which causes overheating which causes more boiling ..... and eventually coolant dumping out on the floor. A pressure test of the cooling system would confirm whether the rad cap is leaking. However, visual inspection of the underside of the rad cap may also reveal that it is leaking. During the work on the car the gasket under the cap may have been disturbed or damaged resulting in a sealing failure.

If the expansion bottle is venting due to overheating the venting will occur at the top of the bottle around the pressure cap. From the photo, there are no obvious signs of venting around the top of the bottle; but, things are a little dirty so hard to tell. A crack in the expansion bottle can result in coolant loss; but, the original round expansion bottles have been pretty durable. The much much later Volvo tanks with slab sides - not so durable.

[Kevin 1964]

Thanks 142G, since the issue started, I have replaced both the Rad cap and the expansion bottle cap, the bottle itself is OK, unfortunately changing the caps did not help.
Regards the leak, it always comes from the top of the expansion bottle where there are 2 x small holes just below the cap, never the rad cap. To make matters worse, the new cap seems such a good fit, that after the last overflow yesterday, today, I cant get the cap off to check the rad level!
The new thermostat should arrive tomorrow, so I'll try again.