Recently purchased a model year ‘98 Q45 for daily driver duty - test drove great and is in okay condition for 122k miles interior/body wise.

Digging further into it finding some common problems based on the threads I’ve come across. Leaky valve covers on both sides causing oil to drip onto exhaust manifolds, failed hood lifts, suspension will need as refresh sooner than later (S13 suspension bits to come)....

My main concern and item to diagnose right now is the cooling issue. The temp gauge has never increased beyond the half way mark (+/-) however I realized the coolant reservoir was near empty and below the min line. Went ahead and put distilled water in to bring it up to max line and follow FSM procedure of starting car and running to normal temps + rev to 3000k for 10 seconds w/ AC @ 85 and allow car to return to cold and check coolant level again - 4 hours after this procedure the reservoir level was down to half way between min and max and around 10 hours later I check again and coolant level is a couple of inches above min line.

We are going to do a compression test today to diagnose whether there is a potential head issue, which at that point my understanding is we are better off sourcing another Y33 engine and swapping in.

Any thoughts given the compression does check out that could be causing this issue? There is no easily visible areas where hoses or connections are leaking.

You may have just had trapped air. When you refill the reservoir like that, the procedure needs to be done twice to tell if coolant is actually being lost. The first pass will just void whatever air was trapped at the top of the system and suck in coolant to replace it. So naturally the level falls.

https://www.amazon.com/EPAuto-Radiator- ... B01I40ZQWE

Buy one of these. Its also good to point out that the reservoir will fluctuate a bit when going from hot to cold and vice versa. Mine starts at halfway between the min and max and when fully warm it goes to the max line.

There is one tricky bit of hose underneath the manifold but as Vstar said. Bleed the system good to make sure no air is in it.

Also, get a good high mileage oil to see if any seepage from the seals may stop. It's the inexpensive way to go at first without dumping a lot of time/money into the car. My 2 cents anyways

VStar650CL wrote: ↑

Sun Feb 07, 2021 1:13 pm

You may have just had trapped air. When you refill the reservoir like that, the procedure needs to be done twice to tell if coolant is actually being lost. The first pass will just void whatever air was trapped at the top of the system and suck in coolant to replace it. So naturally the level falls.

This. Also, those plastic reservoirs (and the hose that feeds it) are prone to cracking. A small leak, over a few drive cycles, means you're losing a lot of coolant (the radiator keeps dumping coolant in when it's hot, then there's nothing to suck back into the radiator as it cools).

I can't recall is the Y33 has a bleed screw, but if not, get the nose of the car up high and redo the procedure.

Compression test as well as a cooling system pressure test should be done before purchase. Both tools are inexpensive.

+1 for the cooling system funnel. Remember you have 2 "radiator" caps, put the funnel on the one on the upper front of the engine by the alternator (not the one on the radiator).
The reason Greg suggests getting the nose up high is to gravity feed liquid to displace the air. you want the air to escape from the highest altitude point in the system.
If the car has an unknown service history, I'd also do a coolant drain/fill once you confirm no leaks. Best is to remove the threaded plugs from each side of the block to get the best exchange.
If you want your system to run cooler in summer and you don't need to worry about subzero farenheit in your climate, consider a 35/65 coolant to distilled water mixture. You read that right. LESS coolant than water.
As for valve covers, very common on these cars, the good news is the FGY33 is considerably easier than the G50 for this job due to firewall clearances. Plan to remove the upper plenum (there are a few extra gaskets involved) to do the job right and get your intake/EGR passages clean in the process. Correct NGK PFR5G11s too. A little dielectric grease on the porcelain part of the plugs (below the metal terminal) to preclude the dreaded FGY33 coil pack issue.

Thank you for al of the responses. Vstar and others nailed it suggesting it was a result of trapped air. The amount of coolant that was disappearing was throwing me off as it seemed excessive for it to be a product of air in the system. It’s safe to say the prior owner did not know how to maintain or work on the Q as when I went to check it out and change the battery (ad stated bad charging system), he applauded me for knowing how to remove the top bracket and cables. :O

Did a compression test and it exceeded my expectations - the following was recorded:

Cylinder 1: 175+/-
Cylinder 2: 165+/-
Cylinder 3: 175+/-
Cylinder 4: 175+/-

Cylinder 5: 180+/-
Cylinder 6: 175+/-
Cylinder 7: 165+/-
Cylinder 8: 175+/-

Could not find in the service manual which cylinders are designated which number however the above is based on cylinders 1-4 being the drivers side with 1 being closest to headlights and 4 being closest to firewall. 5-8 is passenger side with 5 being closest to headlight, 8 closest to firewall.

I will be doing a coolant pressure test sometime in the near future however completing the proper coolant fill process has ceased the “disappearing coolant” concerns.

Car drove great after reassembling post compression check. Ordering valve cover gaskets, PCV valves, and looking to order the upper/lower plenum gaskets as well + standard coolant and oil flushes just to get the service history documented and able to be recorded more accurately.

I was able to find the OEM valve cover gaskets however am having difficulties with OEM plenum gaskets. Using parts.infinitiusa and they show 14035/14035P for these parts but then follow it with a statement this is for 2000-2001 only. Interested to hear where you guys source your parts and if OEM plenum gaskets cannot be found what brands have been tried and tested as a second alternative.

Thank you in advance!

3Q Jay wrote: ↑

Mon Feb 08, 2021 9:43 am

+1 for the cooling system funnel. Remember you have 2 "radiator" caps, put the funnel on the one on the upper front of the engine by the alternator (not the one on the radiator).
The reason Greg suggests getting the nose up high is to gravity feed liquid to displace the air. you want the air to escape from the highest altitude point in the system.
If the car has an unknown service history, I'd also do a coolant drain/fill once you confirm no leaks. Best is to remove the threaded plugs from each side of the block to get the best exchange.
If you want your system to run cooler in summer and you don't need to worry about subzero farenheit in your climate, consider a 35/65 coolant to distilled water mixture. You read that right. LESS coolant than water.
As for valve covers, very common on these cars, the good news is the FGY33 is considerably easier than the G50 for this job due to firewall clearances. Plan to remove the upper plenum (there are a few extra gaskets involved) to do the job right and get your intake/EGR passages clean in the process. Correct NGK PFR5G11s too. A little dielectric grease on the porcelain part of the plugs (below the metal terminal) to preclude the dreaded FGY33 coil pack issue.

Will be running a lower coolant/distilled water ratio as I live in AZ and see 30F at the lowest in my part of the valley for a max of 2-4 months.

Spark plugs are on the list too as PO had NGK BKR5EIX-11 in all cylinders - will be replacing with Laser Platinums.

Sounds good. On your compression results, 1,3,5,7 is the nissan cylinder designation--Driver;s bank fore to aft
for the plenum gaskets, I used:
14032-6P010 upper to lower plenum
GASKET, MANIFLD (2) INF#14035-6P001 for the lower to the heads.
you might consider replacing the KS, fuel hoses, and the lower valley coolant hoses if you go that far. the Vh41DE uses actual steel gaskets from the y-pipe to the heads:
GASKET OUTLET (2) INF#11062-6P001

I'm in the Valley as well (far NW Surprise). Welcome aboard!

3Q Jay wrote: ↑

Mon Feb 08, 2021 1:11 pm

Sounds good. On your compression results, 1,3,5,7 is the nissan cylinder designation--Driver;s bank fore to aft
for the plenum gaskets, I used:
14032-6P010 upper to lower plenum
GASKET, MANIFLD (2) INF#14035-6P001 for the lower to the heads.
you might consider replacing the KS, fuel hoses, and the lower valley coolant hoses if you go that far. the Vh41DE uses actual steel gaskets from the y-pipe to the heads:
GASKET OUTLET (2) INF#11062-6P001

Thanks for the verified part numbers!

AZhitman wrote: ↑

Mon Feb 08, 2021 10:08 pm

I'm in the Valley as well (far NW Surprise). Welcome aboard!

That’s awesome to hear! I’m glad to be doing maintenance items during the best time of year and not sweating it out in the garage in a few months from now doing this.

Had an order ready to go from Infiniti Parts Deals and checked their availability - everything is 9 days out + shipping. Interested to hear what other go to sources you guys have for OEM parts. Tried parts.infinitiusa and a couple others but they were out of one or more of the requested part numbers I need for this refresh.

Ordered a coolant pressure tester as I figure now is the best time to confirm everything is in good working condition while I am in the process of removing Plenum!